Professor John O'Hara

We conducted a systematic review and meta-analysis of randomized clinical trials examining the effect of inorganic nitrate or nitrite supplementation on cognitive function (CF) and cerebral blood flow (CBF). Two databases (PubMed, Embase) were searched for articles from inception until May 2017. Inclusion criteria were: randomized clinical trials; participants >18 years old; trials comparing a nitrate/nitrite intervention with a control. Thirteen and nine trials were included in the meta-analysis to assess CF and CBF, respectively. Random-effects models were used and the effect size described as standardized mean differences (SMDs). A total of 297 participants (median of 23 per trial) were included for CF; 163 participants (median of 16 per trial) were included for CBF. Nitrate/nitrite supplementation did not influence CF (SMD +0.06, 95% CI: -0.06, 0.18, P = 0.32) or CBF under resting (SMD +0.14, 95% CI: -0.13, 0.41, P = 0.31), or stimulated conditions (SMD +0.23, 95% CI: -0.11, 0.56, P = 0.19). The meta-regression showed an inverse association between duration of the intervention and CBF (P = 0.02) but no influence of age, BMI or dose (P < 0.05). Nitrate and nitrite supplementation did not modify CBF or CF. Further trials employing larger samples sizes and interventions with longer duration are warranted.

Carbohydrate (CHO) ingestion during prolonged exercise is common practice amongst athletes and improves endurance performance. Glycogen is a limited energy resource during prolonged exercise and as such sparing glycogen has been proposed as a mechanism behind the ergogenic effect of CHO. However, evidence to support such an effect is equivocal and it appears that the dose of CHO may play an important role in this regard. The aim of this thesis was to investigate a dose response to prolonged exercise CHO ingestion on exogenous CHO, liver and muscle glycogen utilisation and exercise performance.  Two multiple condition studies were conducted consisting of either a 2 or 3 hour continuous period of fixed workload cycling followed by a 30 minute time trial. During the fixed workload period, a placebo solution or various CHO solutions were ingested which had been artificially labelled with a 13Carbon (13C) stable mass isotope tracer. By analysing the appearance of the 13C tracer in expired air and plasma glucose, rates of exogenous CHO, plasma glucose and liver and muscle glycogen were calculated. Study 1 investigated 4 CHO doses (60 to 112.5 g.h-1) using both single and multiple transportable CHO designed to saturate and over saturate the intestinal transport proteins SGLT1 and GLUT5 during 2 hours of continuous cycling at 77% V̇ O2max. Study 2 examined a smaller dose range (80 to 100 g.h-1) in order to provide evidence to the effectiveness of a 90 g.h-1 dose during 3 hours of continuous cycling at 60% VO2max. ̇  In Study 1 the ingestion of multiple transportable CHO at 90 g.h-1 improved performance by 9-15% and spared muscle glycogen relative to the ingestion of glucose only. Fat oxidation was spared relative to placebo ingestion with CHO. It was also seen that increasing CHO dose with ingestion of both single CHO and multiple transportable CHO at rates exceeding intestinal saturation did not further increase exogenous CHO oxidation, and had potentially negative consequences on time trial performance and endogenous substrate (fat and glycogen) oxidation. Study 2 showed that multiple transportable CHO ingestion at 90 g.h-1 produced a small reduction (17.8%) in muscle glycogen oxidation rate and an improvement (3.6 - 7.1%) in mean power output in the time trial, relative to 80 and 100 g.h-1 .  This thesis provides novel evidence that with the right dose of CHO ingestion during prolonged exercise, muscle glycogen was spared, which coincided with improved subsequent time trial performance. Further, the effect of ‘over-dosing’ exogenous CHO intake was potentially detrimental to endogenous substrate oxidation and time trial performance.

The Tokyo 2020 Olympic Games were due to be the hottest on record, with hot (>30 °C) and high-humidity environmental conditions (70-90% relative humidity). Olympic Distance Triathlon comprises a 1.5 km swim, a 40 km bike ride, and a 10 km run performed successively. Prolonged exercise in the heat produces greater physiological and perceptual strain compared to exercising in temperate environmental conditions at the same intensity. Athletes competing in middle- and long-distance events are at a higher risk of reductions in exercise performance and incidence of heat illness compared to short distance events in the heat. Heat acclimation (HA) is the most effective countermeasure to protect athlete health and improve performance. Research on applied and effective HA strategies which confer the necessary heat adaptation responses while still conforming to the ecological training needs of highly trained athletes is limited. The first study (Chapter 4) of this thesis established the reliability of novel blood biomarkers and classical physiological and perceptual markers of heat stress during a new cycling heat stress test (HST) which fixes the intensity relative to body mass. The test offers a reliable assessment tool to evaluate the effectiveness of HA protocols employed. Chapter 5 evaluated whether 5-days isothermic HA was an effective preparation strategy for the Tokyo 2020 Olympic Games in endurance trained athletes. Reduced cardiovascular and perceptual strain, plasma volume expansion and an increase in sweat loss were evident. However, there was no change in body temperature or surrogate biomarkers of physiological stress. Chapter 6 investigated the effectiveness of a novel and ecologically valid 8-day HA strategy which combined modes of HA; isothermic HA and post-temperate exercise hot water immersion (HWI). There was reduced thermal, cardiovascular, and perceptual strain after 4-days HA, with no further improvement at day 8 of HA. Diminished sympathetic activity and fluid-regulatory stress were evident after 8-days HA. However, no change in performance was demonstrated during a 20-km cycling time trial in the heat. This thesis provides practitioners and coaches within British Triathlon Federation a reliable assessment tool of heat dissipation capacity in Tokyo specific environmental conditions. 5-days isothermic HA induced partial HA, affording athletes a time-efficient approach for rapid adaptation. However, a combined HA protocol of isothermic HA and HWI over 4 and 8-days induces superior thermoregulatory, perceptual, and biochemical adaptations. Hence, is the recommended approach for elite triathletes prior to competition at the Tokyo 2020 Games.

The use of global positioning systems (GPS) technology within referees of any sport is limited. Therefore, the purpose of the current study was to evaluate the movement and physiological demands of professional rugby league referees using GPS tracking analysis. Time-motion analysis was undertaken on 8 referees using 5-Hz GPS devices and heart rate monitors throughout a series of Super League matches. 44 data sets were obtained with results identifying similar total distance covered between first and second half periods with a significant (P=0.004) reduction in the number of high velocity efforts performed between 5.51-7.0 m.s-1 (1st=21±8, 2nd=18±8). Mean distance covered from greatest to least distance, was 3 717±432 m, 3 009±402 m, 1 411±231 m, 395±133 m and 120±97 m for the following 5 absolute velocity classifications, respectively; 0.51-2.0 m.s-1; 2.1-4.0 m.s-1: 4.01-5.5 m.s-1; 5.51-7.0 m.s-1; <7.01 m.s-1. Heart rate was significantly (P<0.001) greater in the first (85.5±3.4% maxHR) compared to the second (82.9±3.8% maxHR) half. This highlights the intermittent nature of rugby league refereeing, consisting of low velocity activity interspersed with high velocity efforts and frequent changes of velocity. Training should incorporate interval training interspersing high velocity efforts of varying distances with low velocity activity while trying to achieve average heart rates of ~ 84% maxHR to replicate the physiological demands.

The present study evaluated whether the inclusion of protein (PRO) and amino acids (AA) within a maltodextrin (MD) and galactose (GAL) recovery drink enhanced post-exercise liver and muscle glycogen repletion. A total of seven trained male cyclists completed two trials, separated by 7 d. Each trial involved 2 h of standardised intermittent cycling, followed by 4 h recovery. During recovery, one of two isoenergetic formulations, MD-GAL (0.9 g MD/kg body mass (BM) per h and 0.3 g GAL/kg BM per h) or MD-GAL-PRO+AA (0.5 g MD/kg BM per h, 0.3 g GAL/kg BM per h, 0.4 g whey PRO hydrolysate plus l-leucine and l-phenylalanine/kg BM per h) was ingested at every 30 min. Liver and muscle glycogen were measured after depletion exercise and at the end of recovery using 1H-13C-magnetic resonance spectroscopy. Despite higher postprandial insulin concentations for MD-GAL-PRO+AA compared with MD-GAL (61.3 (se 6.2) v. 29.6 (se 3.0) mU/l, (425.8 (se 43.1) v. 205.6 (se 20.8) pmol/l) P= 0.03), there were no significant differences in post-recovery liver (195.3 (se 2.6) v. 213.8 (se 18.0) mmol/l) or muscle glycogen concentrations (49.7 (se 4.0) v. 51.1 (se 7.9) mmol/l). The rate of muscle glycogen repletion was significantly higher for MD-GAL compared with MD-GAL-PRO+AA (5.8 (se 0.7) v. 3.7 (se 0.6) mmol/l per h, P= 0.04), while there were no significant differences in the rate of liver glycogen repletion (15.0 (se 2.5) v. 13.0 (se 2.7) mmol/l per h). PRO and AA within a MD-GAL recovery drink, compared with an isoenergetic mix of MD-GAL, did not enhance but matched liver and muscle glycogen recovery. This suggests that the increased postprandial insulinaemia only compensated for the lower MD content in the MD-GAL-PRO+AA treatment.

PURPOSE: This study determined the effect of ingesting galactose and glucose 30 min before exercise on exogenous and endogenous fuel use during exercise. METHODS: Nine trained male cyclists completed three bouts of cycling at 60% W(max) for 120 min after an overnight fast. Thirty minutes before exercise, the cyclists ingested a fluid formulation containing placebo, 75 g of galactose (Gal), or 75 g of glucose (Glu) to which (13)C tracers had been added, in a double-blind randomized manner. Indirect calorimetry and isotope ratio mass spectrometry were used to calculate fat oxidation, total carbohydrate (CHO) oxidation, exogenous CHO oxidation, plasma glucose oxidation, and endogenous liver and muscle CHO oxidation rates. RESULTS: Peak exogenous CHO oxidation was significantly higher after Glu (0.68 ± 0.08 g.min(-1), P < 0.05) compared with Gal (0.44 ± 0.02 g.min(-1)); however, mean rates were not significantly different (0.40 ± 0.03 vs. 0.36 ± 0.02 g.min(-1), respectively). Glu produced significantly higher exogenous CHO oxidation rates during the initial hour of exercise (P < 0.01), whereas glucose rates derived from Gal were significantly higher during the last hour (P < 0.01). Plasma glucose and liver glucose oxidation at 60 min of exercise were significantly higher for Glu (1.07 ± 0.1 g.min(-1), P < 0.05, and 0.57 ± 0.08 g.min(-1), P < 0.01) compared with Gal (0.64 ± 0.05 and 0.29 ± 0.03 g.min(-1), respectively). There were no significant differences in total CHO, whole body endogenous CHO, muscle glycogen, or fat oxidation between conditions. CONCLUSION: The preexercise consumption of Glu provides a higher exogenous source of CHO during the initial stages of exercise, but Gal provides the predominant exogenous source of fuel during the latter stages of exercise and reduces the reliance on liver glucose.

This study examined the relationships between selected kinematic and physiological parameters and their influence on performance during incremental exercise in elite swimmers competing at the international level. Eleven men and ten women (all specialized in 200-m events) performed an incremental 7 × 200-m test in their specialized stroke. Stroke rate (SR), stroke length (SL), velocity (V), and blood lactate concentration (BLa) were measured for each 200 m. In addition to the cross-sectional group design, the longitudinal performance of a male swimmer was evaluated by 4 tests during a period of 20 weeks. Stroke rate increased and SL decreased with V, regardless of the age, stroke, or gender of the swimmer. Statistically significant correlations were found between SR and V (p < 0.01; r = 0.66 to 0.99), SR and SL (p < 0.01; r = -0.78 to -0.99), SL and V (except for women's freestyle and breaststroke) (p < 0.01; r = -0.67 to -0.98), and BLa and V (p < 0.01; r = 0.7 to 0.96). Changes in SR and SL were not affected by changes in BLa. Similar velocities were produced with different combinations of SR and SL. The fastest times reached in the test were generally slower than expected, and the performance in the test was not associated with competition performance. The case study revealed similar results to those of the group. The test used in this study was informative with respect to identifying the most economical and effective stroke kinematics combination for slow to submaximal velocities. It is possible that the swimming speeds were not maximal in the final 200-m swim because of cumulative fatigue, which is a major limitation for assessing race pace. An additional test that produces velocities similar to those used in competitions would be more useful for the purpose of providing optimal kinematic information specific to racing speeds, which would facilitate performance improvement through regular monitoring in training.

The utilisation of carbohydrate sources under exercise conditions is of considerable importance in performance sports. Incorporation of optimal profiles of macronutrients can improve endurance performance in athletes. However, gaining an understanding of the metabolic partitioning under sustained exercise can be problematical and isotope labelling approaches can help quantify substrate utilisation. The utilisation of oral galactose was investigated using (13)C-galactose and measurement of plasma galactose and glucose enrichment by liquid chromatography/isotope ratio mass spectrometry (LC/IRMS). As little as 100 μL plasma could readily be analysed with only minimal sample processing. Fucose was used as a chemical and isotopic internal standard for the quantitation of plasma galactose and glucose concentrations, and isotopic enrichment. The close elution of galactose and glucose required a correction routine to be implemented to allow the measurement, and correction, of plasma glucose δ(13)C, even in the presence of very highly enriched galactose. A Bland-Altman plot of glucose concentration measured by LC/IRMS against glucose measured by an enzymatic method showed good agreement between the methods. Data from seven trained cyclists, undergoing galactose supplementation before exercise, demonstrate that galactose is converted into glucose and is available for subsequent energy metabolism.

This study investigated the acute changes in body composition that occur over the course of a competitive season in elite rugby league players. Twenty elite senior players from an English Super League rugby league team underwent a total-body dual-energy X-ray absorptiometry scan at 3 phases of a competitive season: preseason (February), midseason (June), and postseason (September). Body mass (BM), fat mass (FM), lean mass, percentage body fat, and bone mineral content (BMC) were reported at each phase. Between the start and midpoint of the season, BM, lean mass, FM, and body fat percentage showed no significant change (p > 0.05); however, BMC was significantly increased (+0.71%; 30.70 ± 38.00 g; p < 0.05). Between the midseason and postseason phase, BM and BMC showed no significant change (p > 0.05); however, significant changes were observed in lean mass (-1.54%; 1.19 ± 1.43 kg), FM (+4.09%; 0.57 ± 1.10 kg), and body fat percentage (+4.98%; 0.78 ± 1.09%; p < 0.05). The significant changes in body composition seen over the latter stages of the competitive season may have implications for performance capabilities at this important stage of competition. An increase in FM and decrease in lean mass may have a negative effect on the power/BM ratio, and therefore may be a cause for concern for playing, coaching, and medical staff. Coaching and strength and conditioning staff should aim to prescribe appropriate training and nutritional practices with the aim of maintaining the players' optimal body composition until the conclusion of the competitive season, in order that performance capabilities are maximized over the entire competition period.

The purpose of this study was to examine the effects of altitude on dynamic balance and jump performance of a controlled landing during a 12-day high altitude trek. Following a two-legged jump, time to stabilization (5% of body mass for 0.5 s), maximum power, and jump height were measured in 11 participants using a portable force platform at sea level (BL), 3619 m (C1), and 5140 m (C3). Jump performance significantly decreased at C1 and C3 compared to BL (P=0.001). There were no significant differences found in time to stabilization and maximum power with increasing altitude. The present findings indicate that jump performance is significantly decreased with increasing altitude. However, dynamic balance and jump power remain unaffected.

The daily energy requirements for specialist military troops can reach 5000 kcal during training and wartime deployment. Maintaining energy balance is important for health and physical and mental performance in this population, who can effectively be considered as high-performance endurance athletes. In this regard, a balanced diet consisting of 50-60% carbohydrate (CHO), 20-25% protein and 25-30% fat is recommended for endurance athletes in the sporting world. Carbohydrate intake is regarded as a key dietary constituent of the high-performance athlete, as this substrate provides the sole fuel source during high intensity exercise. However, achieving such high CHO intake rates can be challenging, especially when military personnel are in the field. In sports nutrition, athletes commonly use dietary CHO supplements to reduce this deficit. There may be lessons and insight from nutrition and metabolism in sport that could provide Royal Marines, Medical Officers and other embedded medical professionals with strategies to increase CHO intake during intense training or combat situations. This review will highlight the exercise demands of infantry soldiering; it will suggest supplementary strategies to increase CHO intake, in addition to dietary intake, and will describe the metabolic effects of CHO ingestion during prolonged activity in the context of military exercise.

Heart rate variability (HRV) is a useful index of autonomic function and has been linked to the development of high altitude (HA) related illness. However, its assessment at HA has been undermined by the relative expense and limited portability of traditional HRV devices which have mandated at least a minute heart rate recording. In this study, the portable ithlete(™) HRV system, which uses a 55 s recording, was compared with a reference method of HRV which utilizes a 5 min electrocardiograph recording (CheckMyHeart(™) ). The root mean squares of successive R-R intervals (RMSSD) for each device was converted to a validated HRV score (lnRMSSD × 20) for comparison. Twelve healthy volunteers were assessed for HRV using the two devices across seven time points at HA over 10 days. There was no significant change in the HRV values with either the ithlete (P = 0·3) or the CheckMyHeart(™) (P = 0·19) device over the seven altitudes. There was also a strong overall correlation between the ithlete(™) and CheckMyHeart(™) device (r = 0·86; 95% confidence interval: 0·79-0·91). The HRV was consistently, though non-significantly higher with ithlete(™) than with the CheckMyHeart(™) device [mean difference (bias) 1·8 l; 95% CI -12·3 to 8·5]. In summary, the ithlete(™) and CheckMyHeart(™) system provide relatively similar results with good overall agreement at HA.

Summary: Fluid retention is a recognized feature of acute mountain sickness. However, accurate assessment of hydration, including the quantification of body water, has traditionally relied on expensive and non-portable equipment limiting its utility in the field setting. We compared the assessment of total body water (TBW) and their relationship to total body weight using two non-invasive methods using the NICas single-frequency bioimpedance analysis (SF-BIA) system and the BodyStat QuadScan 4000 multifrequency BIA system (MF-BIA). TBW measurements were performed at rest at sea level and at high altitude (HA) at 3833 m postexercise and at rest and thereafter at rest at 4450 m and 5129 m on 47 subjects. The average age was 34·5 ± 9·3 years with an age range of 21-54 years (70·2% male). There were strong correlations between TBW assessment with both methods at sea level (r = 0·90; 95% CI 0·78-0·95: P<0·0001) and at HA (r = 0·92; 0·89-0·94: P<0·0001), however, TBW readings were 0·2 l and 1·91 l lower, respectively, with the NICaS. There was a stronger correlation between TBW and body weight with the QuadScan (r = 0·91; P<0·0001) than with the NICaS (r = 0·83; P<0·0001). The overall agreement between the two TBW methods was good, but the 95% confidence intervals around these agreements were relatively wide. We conclude that there was reasonable agreement between the two methods of BIA for TBW, but this agreement was lower at HA.

Summary

Fluid retention is a recognized feature of acute mountain sickness. However, accurate assessment of hydration, including the quantification of body water, has traditionally relied on expensive and non‐portable equipment limiting its utility in the field setting. We compared the assessment of total body water (TBW) and their relationship to total body weight using two non‐invasive methods using the NICas single‐frequency bioimpedance analysis (SF‐BIA) system and the BodyStat QuadScan 4000 multifrequency BIA system (MF‐BIA). TBW measurements were performed at rest at sea level and at high altitude (HA) at 3833 m postexercise and at rest and thereafter at rest at 4450 m and 5129 m on 47 subjects. The average age was 34·5 ± 9·3 years with an age range of 21–54 years (70·2% male). There were strong correlations between TBW assessment with both methods at sea level (r = 0·90; 95% CI 0·78–0·95: P<0·0001) and at HA (r = 0·92; 0·89–0·94: P<0·0001), however, TBW readings were 0·2 l and 1·91 l lower, respectively, with the NICaS. There was a stronger correlation between TBW and body weight with the QuadScan (r = 0·91; P<0·0001) than with the NICaS (r = 0·83; P<0·0001). The overall agreement between the two TBW methods was good, but the 95% confidence intervals around these agreements were relatively wide. We conclude that there was reasonable agreement between the two methods of BIA for TBW, but this agreement was lower at HA.

Mellor, Adrian, Christopher Boos, David Holdsworth, Joe Begley, David Hall, Andrew Lumley, Anne Burnett, Amanda Hawkins, John O'Hara, Stephen Ball, and David Woods. Cardiac biomarkers at high altitude. High Alt Med Biol 15:452-458, 2014. - Background: Classically, biomarkers such as the natriuretic peptides (NPs) BNP/NT-proBNP are associated with the diagnosis of heart failure and hs-cTnT with acute coronary syndromes. NPs are also elevated in pulmonary hypertension. High pulmonary artery systolic pressure (PASP) is a key feature of high altitude pulmonary edema (HAPE), which may be difficult to diagnose in the field. We have previously demonstrated that NPs are associated with high PASP and the presence of acute mountain sickness (AMS) in a small cohort at HA. We aimed to investigate the utility of several common cardiac biomarkers in diagnosing high PASP and AMS. Methods: 48 participants were assessed post-trekking and at rest at three altitudes: 3833 m, 4450 m, and 5129 m. NPs, hs-cTnT and hsCRP, were quantified using immunoassays, PASP was measured by echocardiography, and AMS scores were recorded. Results: Significant changes occurred with ascent in NPs, hs-cTnT, hsCRP (all p<0.001) and PASP (p=0.006). A high PASP (≥40 mm Hg) was associated with higher NPs, NT-proBNP: 137±195 vs. 71.8±68 (p=0.001); BNP 15.3±18.1 vs. 8.7±6.6 (p=0.001). NPs were significantly higher in those with AMS or severe AMS vs. those without (severe AMS: NT-proBNP: 161.2±264 vs. 76.4±82.5 (p=0.008)). The NPs correlated with hsCRP. cTnT increased with exercise at HA and was also higher in those with a high PASP (13.8±21 vs. 7.8±6.5, p=0.018). Conclusion: The NPs and hs-cTnT are associated with high PASP at HA and the NPs with AMS.

Background: There is a widely held belief that strenuous exercise should be avoided on arrival at high altitude (HA) and during acclimatization. Data from chamber studies are contradictory and the studies are usually of short duration, therefore differing from the " real world. " Methods: We studied 48 trekkers during a 10-d ascent to 16,827 ft (5129 m) in the Cordillera Real area of Bolivia. Borg Rating of Perceived Exertion (RPE) scores were recorded for the hardest perceived exertion during the day after ascents to 12,576, 14,600, and 16,827 ft (3833, 4450, and 5129 m). Heart rate, SpO2 , and Lake Louise Score (LLS) were recorded simultaneously. Statistical testing was performed using SPSS 21 software. A P - value of ≤ 0.05 was deemed significant. Results: Acute mountain sickness (AMS) rates were higher after trekking days with higher levels of perceived exertion. The LLS was higher in those with a Borg RPE score ≥ 15 both following exercise (mean LLS 2.6 vs. 1.7) and at rest the following day (mean LLS 2.7 vs. 1.7). Heart rate was higher in those with high Borg RPE scores (80 vs. 87) and oxygen saturations lower at rest (86 vs. 83) the following morning. Discussion: This data lends weight to the advice of moderate exertion during a trek to HA and suggests that reducing perceived exertion may reduce AMS.

Our objective was to evaluate the utility of the natriuretic peptides BNP (brain natriuretic peptide) and NT-proBNP as markers of pulmonary artery systolic pressure (PASP) in trekkers ascending to high altitude (HA). 20 participants had BNP and NT-proBNP assayed and simultaneous echocardiographic assessment of PASP performed during a trek to 5150 m. PASP increased significantly (p=0.006) with ascent from 24+/-4 to 39+/-11 mm Hg at 5150 m. At 5150 m those with a PASP>/=40 mm Hg (n=8) (versus those with PASP<40 mm Hg) had higher post-exercise BNP (pg/ml): 54.5+/-36 vs. 13.4+/-17 (p=0.012). Their resting BNP at 5150 m was also higher: 57.3+/-43.4 vs. 12.6+/-13 (p=0.017). In those with a pathological (>/=400 pg/ml) rise in NT-proBNP at 5150 m (n=4) PASP was significantly higher: 45.9+/-7.5 vs. 32.2+/-6.2 mm Hg (p=0.015). BNP and NT-proBNP may reflect elevated PASP, a central feature of high altitude pulmonary oedema, at HA.

Intense exercise is an integral part of high altitude (HA) exposure and is linked to an increased risk of acute mountain sickness (AMS)1. Quantification of exercise intensity at HA is challenging and prone to marked inter-individual variability due to subjectivity in reporting. The Borg rating of perceived exertion (RPE) scale allows for a quantitative measure of exercise intensity2 however its relationship to heart rate (HR) during exercise at HA is not well established3. This study aimed to assess the relationship between HR and Borg RPE scale during exercise at HA. Seventeen healthy and physically active adults (11 male, 6 female), with median age 32 (range 25-54 years) were studied at terrestrial HA during unacclimatised ascent from 1180 to 5140m over 11 separate trekking days. Subjects were issued with individual Polar watches (RS400) which were linked to a Polar (H1) chest worn heart rate monitor and set to record continuously throughout the trek. The overall RPE was quantified using Borg 6-20 scale and was collected at random intervals during the trek. HR data was subsequently analysed and paired to the corresponding RPE, although HR between these intervals was not analysed. 419 paired observations of HR and RPE were recorded. The median RPE score was 10.0 (IQR 9.0-11.0) with an average HR (mean ± SD) of 110 ± 18bpm. There was a significant increase in HR with increasing RPE category: 100 ± 17bpm (RPE 6-9), 114 ± 14bpm (RPE 10-13) and 131 ± 12bpm (RPE >14; ANOVA p <0.0001). HR and RPE significantly correlated across all altitudes (Spearman’s rho =0 49: 95% CI 0.41-0.56: p<0.001) and at each altitude range rho=0.44 at 1200-3500m (n=221; p<0.01,), 0.34 at 3600-4600m (n=36; p=0.043) and 0.57 at 4600-5140m (n=162; p<0.01). The Borg 6-20 RPE scale significantly correlated with HR at HA and appears to be an effective method for monitoring exercise intensity at HA. RPE monitoring should be considered as a useful prevention and risk stratification tool for the development of AMS.

PURPOSE: Heat stress exacerbates post-exercise hypotension (PEH) and cardiovascular disturbances from elevated body temperature may contribute to exertion-related incapacity. Mast cell degranulation and muscle mass are possible modifiers, though these hypotheses lack practical evidence. This study had three aims: (1) to characterise pre-post-responses in histamine and mast cell tryptase (MCT), (2) to investigate relationships between whole body muscle mass (WBMM) and changes in blood pressure post-marathon, (3) to identify any differences in incapacitated runners. METHODS: 24 recreational runners were recruited and successfully completed the 2019 Brighton Marathon (COMPLETION). WBMM was measured at baseline. A further eight participants were recruited from incapacitated runners (COLLAPSE). Histamine, MCT, blood pressure, heart rate, body temperature and echocardiographic measures were taken before and after exercise (COMPLETION) and upon incapacitation (COLLAPSE). RESULTS: In completion, MCT increased by nearly 50% from baseline (p = 0.0049), whereas histamine and body temperature did not vary (p > 0.946). Systolic (SBP), diastolic (DBP) and mean (MAP) arterial blood pressures and systemic vascular resistance (SVR) declined (p < 0.019). WBMM negatively correlated with Δ SBP (r = - 0.43, p = 0.046). For collapse versus completion, there were significant elevations in MCT (1.77 ± 0.25 μg/L vs 1.18 ± 0.43 μg/L, p = 0.001) and body temperature (39.8 ± 1.3 °C vs 36.2 ± 0.8 °C, p < 0.0001) with a non-significant rise in histamine (9.6 ± 17.9 μg/L vs 13.7 ± 33.9 μg/L, p = 0.107) and significantly lower MAP, DBP and SVR (p < 0.033). CONCLUSION: These data support the hypothesis that mast cell degranulation is a vasodilatory mechanism underlying PEH and exercise associated collapse. The magnitude of PEH is inversely proportional to the muscle mass and enhanced by concomitant body heating.

BACKGROUND: Medical personnel may find it challenging to distinguish severe Exertional Heat Illness (EHI), with attendant risks of organ-injury and longer-term sequalae, from lesser forms of incapacity associated with strenuous physical exertion. Early evidence for injury at point-of-incapacity could aid the development and application of targeted interventions to improve outcomes. We aimed to investigate whether biomarker surrogates for end-organ damage sampled at point-of-care (POC) could discriminate EHI versus successful marathon performance. METHODS: Eight runners diagnosed as EHI cases upon reception to medical treatment facilities and 30 successful finishers of the same cool weather marathon (ambient temperature 8 rising to 12 ºC) were recruited. Emerging clinical markers associated with injury affecting the brain (neuron specific enolase, NSE; S100 calcium-binding protein B, S100β) and renal system (cystatin C, cysC; kidney-injury molecule-1, KIM-1; neutrophil gelatinase-associated lipocalin, NGAL), plus copeptin as a surrogate for fluid-regulatory stress, were sampled in blood upon marathon collapse/completion, as well as beforehand at rest (successful finishers only). RESULTS: Versus successful finishers, EHI showed significantly higher NSE (10.33 [6.37, 20.00] vs. 3.17 [2.71, 3.92] ug.L-1, P<0.0001), cysC (1.48 [1.10, 1.67] vs. 1.10 [0.95, 1.21] mg.L-1, P = 0.0092) and copeptin (339.4 [77.0, 943] vs. 18.7 [7.1, 67.9] pmol.L-1, P = 0.0050). Discrimination of EHI by ROC (Area-Under-the-Curve) showed performance that was outstanding for NSE (0.97, P<0.0001) and excellent for copeptin (AUC = 0.83, P = 0.0066). CONCLUSIONS: As novel biomarker candidates for EHI outcomes in cool-weather endurance exercise, early elevations in NSE and copeptin provided sufficient discrimination to suggest utility at point-of-incapacity. Further investigation is warranted in patients exposed to greater thermal insult, followed up over a more extended period.

Introduction: High-altitude (HA) exposure affects heart rate variability (HRV) and has been inconsistently linked to acute mountain sickness (AMS). The influence of increasing HA exposure on ultra-short HRV and its relationship to gold standard HRV measures at HA has not been examined. Methods: This was a prospective observational study of adults aged ≥ 18 years undertaking a HA trek in the Dhaulagiri region of the Himalayas. Cardiac inter-beatintervals were obtained from a 10-s recording of supra-systolic blood pressure (Uscom BP+ device) immediately followed by 300 s single lead ECG recording (CheckMyHeart device). HRV was measured using the RMSSD (root mean square of successive differences of NN intervals) at sea level (SL) in the United Kingdom and at 3,619, 4,600, and 5,140 m at HA. Oxygen saturations (SpO2) were measured using finger-based pulse oximetry. The level of agreement between the 10 and 300 s RMSSD values were examined using a modified Bland–Altman relative-difference analysis. Results: Overall, 89 participants aged 32.2 ± 8.8 years (range 18–56) were included of which 70.8% were men. HA exposure (SL vs. 3,619 m) was associated with an initial increase in both 10 s (45.0 [31.0–82.0]) vs. 58.0 [33.0–119.0] ms) and 300 s (45.67 [33.24–70.32] vs. 56.48 [36.98–102.0] ms) in RMSSD. Thereafter at 4,600 and 5,140 m both 10 and 300 s RMSSD values were significantly lower than SL. From a total of 317 paired HRV measures the 10 and 300 s RMSSD measures were moderately correlated (Spearman = 0.66; 95% CI: 0.59–0.72; p < 0.0001). The median difference (bias) in RMSSD values (300 s − 10 s) was −2.3 ms with a lower and upper limit of agreement of −107.5 and 88.61 ms, respectively with no differences with altitude. Overall, 293/317 (92.4%) of all paired HRV values fell within the 95% CI limits of agreement. Neither HRV method was predictive of AMS. Conclusion: Increasing HA affects ultra-short HRV in a similar manner to gold-standard 300 s. Ultra-short HRV has a moderate agreement with 300 s measurements. HRV did not predict AMS.

Travel to high altitude is increasingly popular. With this comes an increased incidence of high-altitude illness and therefore an increased need to improve our strategies to prevent and accurately diagnose these. In this review, we provide a summary of recent advances of relevance to practitioners who may be advising travelers to altitude. Although the Lake Louise Score is now widely used as a diagnostic tool for acute mountain sickness (AMS), increasing evidence questions the validity of doing so, and of considering AMS as a single condition. Biomarkers, such as brain natriuretic peptide, are likely correlating with pulmonary artery systolic pressure, thus potential markers of the development of altitude illness. Established drug treatments include acetazolamide, nifedipine, and dexamethasone. Drugs with a potential to reduce the risk of developing AMS include nitrate supplements, propagators of nitric oxide, and supplemental iron. The role of exercise in the development of altitude illness remains hotly debated, and it appears that the intensity of exercise is more important than the exercise itself. Finally, despite copious studies demonstrating the value of preacclimatization in reducing the risk of altitude illness and improving performance, an optimal protocol to preacclimatize an individual remains elusive.

The binding of high-mobility group box-1 (HMGB-1) to the membrane receptor for advanced glycation end-products (mRAGE) is a key early mediator of non-infectious inflammation and its triggers include ischaemia/hypoxia. The effects of acute hypoxia on soluble RAGE (sRAGE) are unknown. Fourteen healthy adults (50% women; 26.6±3.8 years) were assessed at baseline normoxia (T0), followed by four time-points (T90, 95, 100 and 180 minutes) over three hours of continuous normobaric hypoxia (NH, 4450m equivalent) and again 60 minutes after return to normoxia (T240). A 5-minute exercise step-test was performed during NH at T90. Plasma concentrations of HMGB-1, sRAGE VCAM-1, ICAM-1, VEGF IL-8 and IL-13 were measured using venous blood. Arterial and tissue oxygen saturations were measured using pulse oximetry (SpO2) and near-infrared spectroscopy (StO2) respectively. NH led to a significant reduction in SpO2, StO2, sRAGE and VEGF, which was compounded by exercise, before increasing to baseline values with normoxic restoration (T240). NH-Exercise led to a paired increase in HMGB-1. sRAGE inversely correlated with HMGB-1 (r=-0.32; p=0.006), heart rate (r=-0.43; p=0.004) but was not linked to SpO2 or StO2. In conclusion short-term NH leads to a fall in sRAGE and VEGF concentrations with a transient rise post NH-exercise in HMGB-1.

INTRODUCTION: Medical Emergency Response Team (MERT) helicopters fly at altitudes of 3,000m in Afghanistan (9,843ft). Civilian hospitals and disaster-relief surgical teams may have to operate at such altitudes or even higher. Mild hypoxia has been seen to affect the performance of novel tasks at flight levels as low as 5,000ft. Aeromedical teams frequently work in unpressurised environments; it is important to understand the implications of this mild hypoxia and investigate whether supplementary oxygen systems are required for some or all of the team members. METHODS: Ten UK orthopaedic surgeons were recruited and in a double blind randomised experimental protocol, were acutely exposed for 45 minutes to normobaric hypoxia (fraction of inspired oxygen (FiO2) ~14.1% - equivalent to 3000m/10,000ft) or normobaric normoxia (sea-level). Basic physiological parameters were recorded. Subjects completed validated tests of verbal working memory capacity (VWMC) and also applied an orthopaedic external fixator (Hoffmann® 3, Stryker UK) to a plastic tibia under test conditions. RESULTS: Significant hypoxia was induced with the reduction of FiO2 to ~14.1% (SpO2 87% vs. 98%). No effect of hypoxia on VWMC was observed. The pin-divergence score (a measure of frame asymmetry) was significantly greater in hypoxic conditions (4.6mm) compared to sea level (3.0mm), there was no significant difference in the penetrance depth (16.9 vs. 17.2mm). One frame would have failed early. DISCUSSION: We believe that surgery at an altitude of 3000m when unacclimated individuals are acutely exposed to atmospheric hypoxia for 45 minutes, can likely take place without supplemental oxygen use but further work is required.

This study evaluated the effects of the pre-exercise (30 minutes) ingestion of galactose (Gal) or glucose (Glu) on endurance capacity as well as glycemic and insulinemic responses. Ten trained male cyclists completed 3 randomized high-intensity cycling endurance tests. Thirty minutes before each trial, cyclists ingested 1 L of either 40 g of glucose, 40 g of galactose, or a placebo in a double-blind manner. The protocol comprised 20 minutes of progressive incremental exercise (70-85% maximal power output [Wmax]); ten 90-second bouts at 90% Wmax, separated by 180 seconds at 55% Wmax; and 90% Wmax until exhaustion. Blood samples were drawn throughout the protocol. Times to exhaustion were longer with Gal (68.7 ± 10.2 minutes, p = 0.005) compared with Glu (58.5 ± 24.9 minutes), with neither being different to placebo (63.9 ± 16.2 minutes). Twenty-eight minutes after Glu consumption, plasma glucose and serum insulin concentrations were higher than with Gal and placebo (p < 0.001). After the initial 20 minutes of exercise, plasma glucose concentrations increased to a relative hyperglycemia during the Gal and placebo, compared with Glu condition. Higher plasma glucose concentrations during exercise, and the attenuated serum insulin response at rest, may explain the significantly longer times to exhaustion produced by Gal compared with Glu. However, neither carbohydrate treatment produced significantly longer times to exhaustion than placebo, suggesting that the pre-exercise ingestion of galactose and glucose alone is not sufficient to support this type of endurance performance.

The potential for imprecision in the estimation of hydration status from changes in body mass has been outlined previously but the equations derived from these derivations appear inconsistent. Reconciliation of body mass loss in terms of sweat loss and effective body water loss is possible from specific equation sets provided that gains and losses of both body mass and water used in the derivation of sweat loss and to derive effective body water loss are in inclusive equation sets. This is obligatory so that mass and water changes as quantifiable determinants are consistent with both internal processes and external gains and losses. Thus, body mass loss, substrate oxidation, metabolic water, and all the terms used in simultaneous equation sets have to be reconciled not only as identical variables but mathematically balance exactly. The revised equation for effective body water loss given here is different from that originally proposed. Metabolic water is part of body mass loss corrected for substrate oxidation, fluid ingestion, and respiratory water to derive sweat loss and it may not be justified to also include water associated with glycogen as releasable bound water. Accordingly, our calculated effective body water loss is substantially a greater loss than originally supposed but clearly still less than the simple balance between mass loss and fluid ingested.

The addition of carbohydrate (CHO) to an acute creatine (Cr) loading regimen has been shown to increase muscle total creatine content significantly beyond that achieved through creatine loading alone. However, the potential ergogenic effects of combined Cr and CHO loading have not been assessed. The purpose of this study was to compare swimming performance, assessed as mean swimming velocity over repeated maximal intervals, in high-performance swimmers before and after an acute loading regimen of either creatine alone (Cr) or combined creatine and carbohydrate (Cr + CHO). Ten swimmers (mean ± SD of age and body mass: 17.8 ± 1.8 years and 72.3 ± 6.8 kg, respectively) of international caliber were recruited and were randomized to 1 of 2 groups. Each swimmer ingested five 5 g doses of creatine for 4 days, with the Cr + CHO group also ingesting ∼100 g of simple CHO 30 minutes after each dose of creatine. Performance was measured on 5 separate occasions: twice at "baseline" (prior to intervention, to assess the repeatability of the performance test), within 48 hours after intervention, and then 2 and 4 weeks later. All subjects swam faster after either dietary loading regimen (p < 0.01, both regimens); however, there was no difference in the extent of improvement of performance between groups. In addition, all swimmers continued to produce faster swim times for up to 4 weeks after intervention. Our findings suggest that no performance advantage was gained from the addition of carbohydrate to a creatine-loading regimen in these high-caliber swimmers. © 2005 National Strength & Conditioning Association.

Introduction There appears to be a dose dependent curvilinear exercise performance response to ingested carbohydrate (CHO), with an optimum of 78 g/h (Smith et al., 2013). However, the physiological mechanisms underpinning performance gains are unclear and fuel use responses to glucose and mixtures including fructose have not been investigated fully. This study investigated the effect of CHO dose on fuel selection during exercise, in particular exogenous and endogenous (liver and muscle) CHO oxidation. Methods Ten trained male cyclists (VO2max: 61.6 ± 7.4 ml/kg/min) cycled on 4 occasions at 77% VO2max for 2 hours after an overnight fast. From 15 min into exercise and every 15 min thereafter, either 60 g/h glucose (LG), 75 g/h glucose (HG), 90 g/h glucose/fructose (LGF; 2:1 ratio) or 112.5 g/h glucose/fructose (HGF; 2:1 ratio) was ingested in a double-blind randomised order. The formulations contained 13C tracers and were designed to saturate and over saturate intestinal transporters for each hexose. Total, exogenous, endogenous (muscle and liver) CHO oxidation, and total fat oxidation were computed using indirect calorimetry and isotope ratio mass spectrometry. Results Total CHO oxidation was elevated, and total fat oxidation suppressed in HGF relative to all other conditions (CHO 24.9-41.8 g/h higher, Fat 7.9-11.3 g/h lower: both ES > 0.78). Exogenous oxidation was unchanged with higher dose glucose (LG = 41.2, HG = 41.4 g/h, ES = 0.02) and reduced with higher dose glucose/fructose (LGF = 67.7, HGF = 59.2 g/h ES = 0.48). Increasing CHO dose beyond intestinal saturation increased muscle glycogen utilisation for both glucose and glucose/fructose ingestion (125.1±22.6 vs. 109.9±26.9 g/h for glucose, ES=0.59; 129.5±22.6 vs. 100.3±23.1 g/h for glucose/fructose, ES=1.28). Liver glycogen oxidation was reduced with LG vs. HG (20.9±5.6 vs. 24.4±10.1 g/h; ES=0.43), but increased with HGF vs. LGF (30.5±17.7 vs. 19.3±9.4 g/h; ES=0.43). Discussion Increasing CHO ingestion rate for each hexose was not associated with higher exogenous oxidation. When the CHO dose was increased for both glucose and glucose/fructose, endogenous glycogen oxidation was increased, primarily due to an increased reliance on muscle glycogen. This with high liver glycogen and reduced fat oxidation for very high dose glucose/fructose is not ideal for exercise performance. References Smith J, Pascoe D Passe D, Ruby B, Stewart L, Baker L, Zachwieja J (2013). Curvilinear Dose-Response Relationship of Carbohydrate (0-120g/h) and Performance. Med Sci Sports Exerc 45(2): 336-341

Purpose: This study investigated the effect of carbohydrate supplementation on substrate oxidation during exercise in hypoxia after pre-exercise breakfast consumption and omission. Methods: Eleven men walked in normobaric hypoxia (FiO2 ~11.7%) for 90-min at 50% of hypoxic V̇O2max. Participants were supplemented with a carbohydrate beverage (1.2g·min-1 glucose) and a placebo beverage (both enriched with U-13C6 D-glucose) after breakfast consumption and after omission. Indirect calorimetry and isotope ratio mass spectrometry were used to calculate carbohydrate (exogenous and endogenous (muscle and liver)) and fat oxidation. Results: In the first 60-min of exercise, there was no significant change in relative substrate oxidation in the carbohydrate compared with placebo trial after breakfast consumption or omission (both p = 0.99). In the last 30-min of exercise, increased relative carbohydrate oxidation occurred in the carbohydrate compared with placebo trial after breakfast omission (44.0 ± 8.8 vs. 28.0 ± 12.3, p < 0.01) but not consumption (51.7 ± 12.3 vs. 44.2 ± 10.4, p = 0.38). In the same period, a reduction in relative liver (but not muscle) glucose oxidation was observed in the carbohydrate compared with placebo trials after breakfast consumption (liver: 7.7 ± 1.6% vs. 14.8 ± 2.3%, p < 0.01; muscle: 25.4 ± 9.4% vs. 29.4 ± 11.1%, p = 0.99) and omission (liver: 3.8 ± 0.8% vs. 8.7 ± 2.8%, p < 0.01; muscle: 19.4 ± 7.5% vs. 19.2 ± 12.2%, p = 0.99). No significant difference in relative exogenous carbohydrate oxidation was observed between breakfast consumption and omission trials (p = 0.14). Conclusion: In acute normobaric hypoxia, carbohydrate supplementation increased relative carbohydrate oxidation during exercise (> 60 min) after breakfast omission, but not consumption.

Background: Fractional exhaled nitric oxide (FeNO) is a simple tool that has an established role in the assessment of airway inflammation in athletes. Specifically, FeNO provides information concerning asthma phenotypes, aetiology of respiratory symptoms, response to anti-inflammatory agents, course of disease and adherence to medication. It is recognised that FeNO can be influenced by a variety of external factors (e.g. atopic status, exercise, respiratory tract infection), however, there remains limited research concerning the impact of dietary nitrate ingestion. The primary aim of this study was therefore to evaluate the effect of acute dietary nitrate supplementation on FeNO and resting pulmonary function parameters. Method: The study was conducted as a randomised double-blind placebo-controlled trial. Thirty male endurance trained athletes (age: 28 ± 6 yrs; BMI: 23 ± 2 kg.m-2) free from cardio-respiratory and metabolic disease, and stable at time of study entry (i.e. entirely asymptomatic without recent respiratory tract infection) attended the laboratory on two separate occasions. On arrival to the laboratory, athletes consumed either 140ml nitrate-rich beetroot juice (15.2 mmol nitrate) (NIT) or nitrate-depleted beetroot juice (0 mmol nitrate) (PLA). In accordance with international guidelines all athletes performed resting FeNO and forced spirometry (2.5hrs post ingestion). Airway inflammation was evaluated using established FeNO thresholds: (intermediate [≥25ppb] and high [>50ppb]). Results: All athletes demonstrated normal baseline lung function (FEV1 % predicted >80%). A three-fold rise in resting FeNO was observed following NIT (median [IQR]): 32ppb [37] in comparison to PLA: 10ppb [12] (P<0.001). Twenty-two athletes (73%) presented with raised FeNO following NIT (intermediate: n = 13; high: n = 9) in comparison to four athletes (13%) following PLA (intermediate: n = 2; high: n = 2). Despite this, no difference was observed in any pulmonary function parameters between visits (P>0.05). Conclusion: Dietary nitrate ingestion should be considered when employing FeNO for the assessment of airway health in athletes. Our findings have implications concerning the decision to initiate or modify inhaler therapy. Further research is therefore required to determine the impact of chronic dietary nitrate

Purpose: This study evaluated whether glycogen-associated water is a protected entity not subject to normal osmotic homeostasis. An investigation into practical and theoretical aspects of the functionality of this water as a determinant of osmolality, dehydration, and glycogen concentration was undertaken. Methods: In vitro experiments were conducted to determine the intrinsic osmolality of glycogen–potassium phosphate mixtures as would be found intra-cellularly at glycogen concentrations of 2% for muscle and 5 and 10% for liver. Protected water would not be available to ionic and osmotic considerations, whereas free water would obey normal osmotic constraints. In addition, the impact of 2 L of sweat loss in situations of muscle glycogen repletion and depletion was computed to establish whether water associated with glycogen is of practical benefit (e.g., to increase “available total body water”). Results: The osmolality of glycogen–potassium phosphate mixtures is predictable at 2% glycogen concentration (predicted 267, measured 265.0 ± 4.7 mOsmol kg

−1

This study investigated the effect of carbohydrate (CHO) dose and composition on fuel selection during exercise, specifically exogenous and endogenous (liver and muscle) CHO oxidation. Ten trained males cycled in a double-blind randomized order on 5 occasions at 77% VO2max for 2 h, followed by a 30-min time-trial (TT) while ingesting either 60 g h 1 (LG) or 75 g h 1 13Cglucose (HG), 90 g h 1 (LGF) or 112.5 g h 1 13C-glucose-13C-fructose ([2:1] HGF) or placebo. CHO doses met or exceed reported intestinal transporter saturation for glucose and fructose. Indirect calorimetry and stable mass isotope [13C] tracer techniques were utilized to determine fuel use. TT performance was 93% “likely/probable” to be improved with LGF compared with the other CHO doses. Exogenous CHO oxidation was higher for LGF and HGF compared with LG and HG (ES > 1.34, P < 0.01), with the relative contribution of LGF (24.5 5.3%) moderately higher than HGF (20.6 6.2%, ES = 0.68). Increasing CHO dose beyond intestinal saturation increased absolute (29.2 28.6 g h 1, ES = 1.28, P = 0.06) and relative muscle glycogen utilization (9.2 6.9%, ES = 1.68, P = 0.014) for glucose-fructose ingestion. Absolute muscle glycogen oxidation between LG and HG was not significantly different, but was moderately higher for HG (ES = 0.60). Liver glycogen oxidation was not significantly different between conditions, but absolute and relative contributions were moderately attenuated for LGF (19.3 9.4 g h 1, 6.8 3.1%) compared with HGF (30.5 17.7 g h 1, 10.1 4.0%, ES = 0.79 & 0.98). Total fat oxidation was suppressed in HGF compared with all other CHO conditions (ES > 0.90, P = 0.024–0.17). In conclusion, there was no linear dose response for CHO ingestion, with 90 g h 1 of glucose-fructose being optimal in terms of TT performance and fuel selection.

Background: A recent commentary has been published on our meta-analysis, which investigated substrate oxidation during exercise matched for relative intensities in hypoxia compared with normoxia. Within this commentary, the authors proposed that exercise matched for absolute intensities in hypoxia compared with normoxia, should have been included within the analysis, as this model provides a more suitable experimental design when considering nutritional interventions in hypoxia. Main body: Within this response, we provide a rationale for the use of exercise matched for relative intensities in hypoxia compared with normoxia. Specifically, we argue that this model provides a physiological stimulus replicable of real world situations, by reducing the absolute workload undertaken in hypoxia. Further, the use of exercise matched for relative intensities isolates the metabolic response to hypoxia, rather than the increased relative exercise intensity experienced in hypoxia when utilising exercise matched for absolute intensities. In addition, we also report previously unpublished data analysed at the time of the original meta-analysis, assessing substrate oxidation during exercise matched for absolute intensities in hypoxia compared with normoxia. Conclusion: An increased reliance on carbohydrate oxidation was observed during exercise matched for absolute intensities in hypoxia compared with normoxia. These data now provide a comparable dataset for the use of researchers and practitioners alike in the design of nutritional interventions for relevant populations.

Purpose: Establish the short-term reliability and acute responsiveness of biomarkers of physiological stress to exercise in the heat. As such, informing their prospective application in research and field settings. Method: Fourteen male endurance trained cyclists/triathletes completed two heat stress tests (HST), separated by 5-7 days. HST’s involved 45-minutes fixed-intensity cycling (2.5W.kg-1) under hot-humid conditions (32oC and 70% relative humidity). Venous blood was drawn pre- and immediately post-HST for the concentration of normetanephrine (NMET), metanephrine (MET), kidney-injurymolecule1(KIM-1),neutrophilgelatinase-associatedlipocalin(NGAL),serumosmolality (Sosmo) and copeptin. Results: No biomarker displayed systematic trial order bias (p ≤ 0.05). The majority of biomarkers had acceptable within-participant variation (CV range: 0.9-14.3%). Copeptin had the lowest short-term variation at rest (CV = 0.9%) and post-HST (CV = 1.2%). However, greater variation was evident in biomarkers MET and KIM-1 at rest (CV = 28.6 & 43.2%) and post-HST (CV = 29.9 & 29.6%), respectively. NMET exhibited very large increases (trial 1 = Δ1048 ± 461; trial 2 = Δ 1067±408)inresponsetoexertionalheatstress(p<0.0001,d=2.8;p<0.0001,d=3.8).Incontrast, KIM-1 demonstrated trivial changes (trial 1 = Δ -3 ± 21; trial 2 = Δ 2 ± 17) in response to exercise in theheat (p=0.53,d=0.1;p=0.60,d=0.1).Conclusion:Eachbiomarker,exceptMETandKIM-1had acceptable reliability at rest and following exercise. In addition, biomarkers NMET, copeptin and NGAL demonstrated large increases in response to exercise in the heat. Thus, these markers can provide accurate and sensitive measurement for wide-spread application in laboratory and field research.

A mixed‐method heat acclimation (HA) protocol may optimise performance by supporting the training taper while promoting thermal adaptation; however, the impact on cardiovascular and fluid‐regulatory adjustments to protect health is unknown. Therefore, we examined the effects of a mixed‐method heat protocol on physiological responses, including cardiovascular and fluid‐regulatory strain with exercise‐heat stress, and self‐paced performance in the heat. Twenty (15 males, five females) triathletes were randomised to 8 days of HA (HOT), or exercise in thermoneutral conditions (TEMP). A heat stress test (HST) comprising 45 min of cycling in a climatic chamber (32°C, 70% relative humidity) was performed on days 1, 5 (HOT only) and 8. Before and after the intervention, a cycling time trial was conducted in the same climatic conditions (days 0 and 10). Venous blood samples were analysed at rest and post‐HST (days 1 and 8 only) for the catecholamine product normetanephrine and the vasopressin surrogate copeptin. Following 7 days of HA (days 1 vs. 8) resting rectal temperature was significantly lower in the HOT compared to the TEMP group (−0.32 ± 0.36°C, P = 0.002). Normetanephrine was 24.3% lower after 7 days of HA (P = 0.012), and copeptin was 53.4% lower at the post‐HST time point (HOT vs. TEMP, P = 0.012). However, HA had no effect (0.3%, P = 0.984) on self‐paced performance in the heat. Mixed‐method HA elicited a progressive reduction in cardiovascular strain and a net reduction in fluid‐regulatory strain without improving self‐paced performance in the heat.

The purpose of the study was to assess the validity and inter-bike reliability of 10 Wattbike cycle ergometers, and to assess the test–retest reliability of one Wattbike. Power outputs from 100 to 1000 W were applied using a motorised calibration rig (LODE) at cadences of 70, 90, 110 and 130 rev · min−1, which created nineteen different intensities for comparison. Significant relationships (P < 0.01, r2 = 0.99) were found between each of the Wattbikes and the LODE. Each Wattbike was found to be valid and reliable and had good inter-bike agreement. Within-bike mean differences ranged from 0.0 W to 8.1 W at 300 W and 3.3 W to 19.3 W at 600 W. When taking into account the manufacturers stated measurement error for the LODE (2%), the mean differences were less than 2%. Comparisons between Wattbikes at each of the nineteen intensities gave differences from 0.6 to 25.5 W at intensities of 152 W and 983 W, respectively. There was no significant difference (P > 0.05) between the measures of power recorded in the test–retest condition. The data suggest that the Wattbike is an accurate and reliable tool for training and performance assessments, with data between Wattbikes being able to be used interchangeably.

Introduction: Few studies have objectively assessed the physiological demands of cricket, particularly during first class matches. An understanding of the specific physiological demands placed on players during match play is useful for setting individual training programmes. Exercise intensity relates to the physical demands of an activity and heart rate (HR) measurement during match play is a convenient way of objectively assessing exercise intensity. Purpose: This study aimed to quantify the exercise intensity of batting in first class cricket and determine any differences in responses between 50 and 20 over formats. Method: Using the Activio Team System, the HR of 5 first-class county batsmen was monitored during competitive 50 and 20 over games. To help identify the factors affecting batting intensity, batting statistics were recorded along with post-match feedback from the batsmen. Findings: HR ranged between 139-154 beats∙min-1 in the 50-over format and 149-167 beats∙min-1 in the 20-over format. The relative time spent in high (>85% HRmax), moderate (70-85% HRmax) and low-intensity (<70% HRmax) HR zones was 19.7 ± 6.9%, 62.6 ± 2.5%, 21.5 ± 7.2% for 50-over cricket and 53.1 ± 24.2%, 44.9 ± 24.2% and 1.35 ± 0.1% during 20-over cricket. During 20-over cricket, batsmen spent significantly more time in high intensity HR zones (p=0.021) and significantly less time in low-intensity HR zones (p=0.015) than during 50-over cricket. The HR when repeatedly scoring runs from running (164-181 beats∙min-1) and hitting 4’s and 6’s (160-177 beats∙min-1) was consistently greater than the HR during low-scoring (145-162 beats∙min-1) or predominantly stationary periods (142-158 beats∙min-1). Discussion: 50-over innings are mainly of low-moderate intensity interspersed with high-intensity periods. Whilst 20-over innings are often much shorter, significantly more time is spent at higher exercise intensities due to shorter and less frequent recovery opportunities. Greater contributions are therefore likely from anaerobic energy systems and repeated sprint ability may be important. Based on the high between and within-subject variability, batting intensity as reflected by measurement of HR, is dependent on the game format, the match situation and the individual. Typical Twenty-20 innings were calculated as lasting 46 ± 0.12 mins on average. Whilst such periods are relatively short compared with other intermittent sports, considerable physical fitness is required to perform consistently within the tight domestic schedule. Based on the HR data, combined net and conditioning sessions can be developed and tailored towards the specific game format in order to facilitate specific adaptations towards batting match play.

The objective of the study was to investigate the impact of static and dynamic stretching singularly or combined within a warm-up on a soccer-specific intermittent protocol (SSIP). Seven semi-professional players aged 21.9(±2.0) years old [height 181.5(±9.4) cm, body mass 74.8(±6.4) kg] following screening and ethical approval, completed a VO2max test and were familiarised with the SSIP. Within a 3-week period, participants undertook 3 different warm-ups, before completing the SSIP, consisting of three bouts of exercise with a 15-min recovery after the 2nd bout to simulate a soccer match. After the 3rd bout participants completed an intermittent time to exhaustion test (ITTE). Warm-ups consisted of 5-min activity, then 10-min of Static Stretches (SS), Dynamic Stretches (DS) and SS+DS (SS-DS) in a randomised-crossover order. Core temperature (Tc) and VO2 were recorded throughout. Testing took place in an environmental chamber, replicating UK conditions (9°C, 50% relative humidity). ITTE was 8.2(±2.3), 9.0(±4.6), and 10.7(±5.9) min for the SS, DS and SS-DS groups. Tc in the SS-DS (38.4±0.3°C) was higher (P<0.05) than the SS (37.9±0.4°C) during the 1st ITT bout. Tc was 38.3(±0.6)°C for the DS condition. Differences in Tc during the first two bouts disappeared in the 3rd. Participants in the DS (78±9.5%) and SS-DS (76.3±15.1%) exercised at a lower (P<0.05) %VO2max than the SS (83.0±15.4%). Combining SS and DS is more beneficial than SS alone during a warm-up, and may be more beneficial than DS alone. A second warm-up is necessary as benefits associated with the initial warm-up dissipate during the half-time break.

Purpose: To evaluate the anthropometric profiles of female surfers and to identify whether any anthropometrical factors might predict competitive ranking. Secondly to evaluate the activity profile of female competitive surfing with respect to environmental conditions using GPS derived measures. Methods: Following institutional ethical approval n = 31 female competitive surfers underwent anthropometric assessment (mean age: 20.49, s = 5.32 years, stature: 165.2, s = 4.8 cm; body mass: 63.0, s = 6.8 Kg) a subsample (n = 22) wore GPS units during competition at four different locations with varied surfing conditions. Results: The mean somatotype values the surfers was found to be (Endo-Meso-Ecto) 4.06 – 4.15 – 2.01. Significant correlations (p <0.05) were found between National ranking and triceps, medial calf skinfolds, sum of six skinfolds, body fat percentage and sum of eight skinfolds. Percentage time sitting, paddling and riding were 62.58% ± 10.18%, 30.70% ± 9.44% and 6.73% ± 2.91% respectively. The mean ride time, maximum ride time, total time spent riding and the total distance surfing were significantly correlated with the round of the competition. Furthermore, the number of rides, time spent riding, percentage of total distance surfing and percentage time riding were correlated with heat placement (p < 0.05). Time spent sitting was associated with poorer heat placements (p < 0.01). Conclusions: Body fat levels are associated with national ranking in competitive female surfers. The number of waves ridden in a heat, the length of the rides and activity levels were significantly related to heat placement and competition progression. Keywords: Body composition; sports; somatotypes; athletic performance/physiology; Muscle, skeletal; body size; body mass index; GPS; wave conditions; competition.

Background: Acute hypoxia leads to a number of recognized changes in cardiopulmonary function, including acute increase in pulmonary artery systolic pressure. However, the comparative responses between men and women have been barely explored.Fourteen young healthy adult Caucasian subjects were studied at sea-level rest and then after >150-minute exposure to acute normobaric hypoxia (NH) equivalent to 4800 m and again at sea-level rest at 2 hours post-NH exposure. Cardiac function, using transthoracic echocardiography, physiological variables, and Lake Louise Scores for acute mountain sickness (AMS) were collected.All subjects completed the study, and there was an equal balance of men (n = 7) and women (n = 7) who were well matched for age (25.9 ± 3.2 vs. 27.3 ± 4.4; p = 0.51). NH exposure led to a significant increase in AMS scores and heart rate, as well as a fall in oxygen saturation, systolic blood pressure, and stroke volume. Stroke volumes and cardiac output were overall significantly higher in men than in women, and acute NH heart rate was higher in women (80.3 ± 10.2 vs. 69.7 ± 10.7/min; p < 0.05). NH led to a significant fall in the estimated left ventricular filling pressure (E/E'), an increase in the septal A' and S' and septal and lateral isovolumic contractile velocities (ICVs), and a fall in the E'A'S' ratio. The mitral E, lateral ICV, and E' velocities were all higher in men. Acute NH led to a significant increase in right ventricular systolic pressure and pulmonary vascular resistance. There was no interaction between NH exposure and sex for any parameters measured.Despite several baseline differences between men and women, the cardiopulmonary effects of acute NH are consistent between men and women.

OBJECTIVE: To examine the effects of consuming a galactose carbohydrate (CHO) drink on substrate oxidation, postexercise satiety, and subsequent energy intake. METHODS: Nine recreationally active eumenorrheic females undertook 3 trials, each consisting of running for 60 minutes at 65% VO2peak followed immediately by a 90-minute rest period. Prior to (300 ml) and at 15-minute intervals during exercise (150 ml), participants consumed either a glucose (GLU: GI 89) or galactose (GAL: GI 20) drink, each of which contained 45 g of CHO, or an artificially sweetened placebo (PLA). Following the rest period, participants were provided with an ad libitum test lunch and asked to record food intake for the remainder of the day. RESULTS: Plasma glucose was significantly greater throughout exercise and rest following the GLU trial compared with the GAL and PLA trials (P < 0.05); however there were no differences in CHO oxidation. Hunger was significantly lower (P < 0.05) throughout the GAL compared to the GLU and PLA trials. There were no significant differences between trials for energy intake during the postexercise meal. Overall net energy balance for the 24 hours was negative in both the GAL (-162 ± 115 kcal; P < 0.05 vs GLU) and PLA trials (-49 ± 160 kcal). CONCLUSIONS: Results demonstrate that ingesting a solution containing GAL before and during exercise can positively impact postexercise satiety and energy balance throughout the day, compared to a more readily available and widely consumed form of CHO. Despite this, there appears to be no apparent benefit in consuming a CHO beverage on fuel utilization for this moderate exercise intensity and duration.

Introduction: There is evidence that intermittent hypoxic exposure (IHE) may improve high altitude (HA) performance. In this study, the effects of short-term IHE through voluntary apnea training on HA-related symptoms, including acute mountain sickness (AMS), were examined for the first time. Methods: Forty healthy adults were randomized to a self-administered apnea training (n = 19) or control (n = 21 no apnea training) group before ascent to an altitude of 5100 m in the Himalayas over 14 days. The apnea training was conducted at sea level (SL) and consisted of five breath holds per day in week 1, seven in week 2, followed by 10 per day from weeks 3 to 6 and until HA exposure. Saturation of arterial oxygen (SpO2), heart rate, sleep quality (Insomnia Severity Index [ISI]), rating of perceived exertion (RPE), blood pressure, and Lake Louise scores were measured at SL (in the United Kingdom) and at HA at 1400, 2700, 3400–3700, 4050–4200, 4800, and 5100–5200 m. Anxiety (Generalized Anxiety Disorder-7 [GAD-7]) scores were examined at SL, 1400, and 5100–5200 m. Results: Apnea training led to a significant increase in the mean longest breath-hold times from baseline (80.42 ± 32.49 [median 87.00] seconds) to the end of week 6 (107.02 ± 43.65 [113.00] seconds), respectively (p = 0.009). There was no significant difference in the prevalence of AMS (8/19 = 42.1% vs. 11/21 = 52.4%; RR 0.80; 95% confidence interval 0.41–1.57: p = 0.80) or in GAD-7, ISI and RPE, SpO2, heart rate, or blood pressure among the apnea versus control groups, respectively, at HA. Conclusions: Apnea training does not lessen HA-related symptoms in healthy adults traveling up to 5200 m. Larger studies using more challenging apnea protocols and at higher altitudes should be considered.

PURPOSE: The aim was to investigate the effect of dietary nitrate supplementation (in the form of beetroot juice, BRJ) for 20 days on salivary nitrite (a potential precursor of bioactive nitric oxide), exercise performance and high altitude (HA) acclimatisation in field conditions (hypobaric hypoxia). METHODS: This was a single-blinded randomised control study of 22 healthy adult participants (12 men, 10 women, mean age 28 ± 12 years) across a HA military expedition. Participants were randomised pre-ascent to receive two 70 ml dose per day of either BRJ (~12.5 mmol nitrate per day; n = 11) or non-nitrate calorie matched control (n = 11). Participants ingested supplement doses daily, beginning 3 days prior to departure and continued until the highest sleeping altitude (4800 m) reached on day 17 of the expedition. Data were collected at baseline (44 m altitude), at 2350 m (day 9), 3400 m (day 12) and 4800 m (day 17). RESULTS: BRJ enhanced the salivary levels of nitrite (p = 0.007). There was a significant decrease in peripheral oxygen saturation and there were increases in heart rate, diastolic blood pressure, and rating of perceived exertion with increasing altitude (p=<0.001). Harvard Step Test fitness scores significantly declined at 4800 m in the control group (p = 0.003) compared with baseline. In contrast, there was no decline in fitness scores at 4800 m compared with baseline (p = 0.26) in the BRJ group. Heart rate recovery speed following exercise at 4800 m was significantly prolonged in the control group (p=<0.01) but was unchanged in the BRJ group (p = 0.61). BRJ did not affect the burden of HA illness (p = 1.00). CONCLUSIONS: BRJ increases salivary nitrite levels and ameliorates the decline in fitness at altitude but does not affect the occurrence of HA illness.

OBJECTIVES: The current study provided a longitudinal evaluation of the anthropometric and fitness characteristics in junior rugby league players across three annual-age categories (i.e., under 13s, 14s and 15s) considering playing position and selection level. DESIGN: Longitudinal design. METHODS: Eighty-one junior rugby league players selected to a talent development programme were tracked over a two year period. Anthropometric (height, sitting height, body mass and sum of four skinfolds) and fitness (lower and upper body power, speed, change of direction speed and maximal aerobic power) characteristics were measured on three occasions (i.e., under 13s, 14s and 15s). Repeated measures multivariate analysis of variance (MANOVA) and multivariate analysis of covariance (MANCOVA; controlling chronological and maturational age) analysed changes across annual-age categories in relation to playing position and selection level. RESULTS: Findings identified significant improvements in anthropometric and fitness characteristics across annual-age categories (p<0.001). MANOVA and MANCOVA analysis identified significant overall effects for playing position (p<0.001) and selection level (p<0.05) throughout the two year period. Interactions between playing position and time were identified for height, vertical jump and estimated V˙O2max (p<0.05). Selection level by time interactions were identified for 20m, 30m and 60m sprint (p<0.05). CONCLUSIONS: This study demonstrates the improvement of anthropometric and fitness characteristics within junior representative rugby league players. Interactive effects for playing position and selection level by time highlight the variation in the development of characteristics that occur during adolescence. Tracking the progression of characteristics longitudinally during adolescence, instead of at one-off time points, may assist selection and/or performance assessments within rugby league and other youth sport contexts.

The present study examined relationships between anthropometric, physiological and selection characteristics of junior (N=683; aged 13–16) representative Rugby League players who underwent a battery of tests (e.g., height; O2max) as part of a national talent development program. Considerate of playing position (categorised as ‘Outside-Backs’, ‘Pivots’, ‘Props’, ‘Backrow’), ‘Props’ were more likely to be the relatively oldest and most mature. However, MANCOVA – with chronological age and maturation controlled – also identified that ‘Props’ were the worst performing on physiological tests. To add, physiological characteristics did not differ according to relative age. Findings suggest that relationships between anthropometric and physiological characteristics are not consistent with biases in selection, which raises issues regarding identification for immediate and long-term player selection and development.

This study evaluated the development of anthropometric and fitness characteristics of 3 individual adolescent junior rugby league players and compared their characteristics with a cross-sectional population matched by age and skill level. Cross-sectional anthropometric and fitness assessments were conducted on 1,172 players selected to the Rugby Football League's talent development program (i.e., the Player Performance Pathway) between 2005 and 2008. Three players of differing relative age, maturational status, and playing position were measured and tracked once per year on 3 occasions (Under 13s, 14s, 15s age categories) and compared against the cross-sectional population. Results demonstrated that the later maturing players increased height (player 1 = 9.2%; player 2 = 7.8%) and a number of fitness characteristics (e.g., 60-m speed-player 1 = -14.9%; player 2 = -9.9%) more than the earlier maturing player (player 3-Height = 2.0%, 60-m sprint = -0.7%) over the 2-year period. The variation in the development of anthropometric and fitness characteristics between the 3 players highlights the importance of longitudinally monitoring individual characteristics during adolescence to assess the dynamic changes in growth, maturation, and fitness. Findings showcase the limitations of short-term performance assessments at one-off time points within annual-age categories, instead of advocating individual development and progression tracking without deselection. Coaches should consider using an individual approach, comparing data with population averages, to assist in the prescription of appropriate training and lifestyle interventions to aid the development of junior athletes.

Athlete development through adolescence can vary greatly because of maturational processes. For example, variation can be observed in anthropometric and fitness measures with later maturing individuals "catching up" their earlier maturing peers at later time points. This study examined a methodological issue concerning how best to assess anthropometric and fitness change (i.e., "across age categories" or "per year") relative to an age and skill-matched population (N = 1,172). Furthermore, it examined changes in anthropometric and fitness characteristics in 3 cases of youth rugby league players (aged 13-15) across a 2-year period. Findings identified the "per year" method as generating less deviated z-scores across anthropometric and fitness measures (e.g., mean change p < 0.001), suggesting less substantial change in case players relative to the population. When applied to additional players, z-score and radar graphs showed developmental variability and longitudinal change. The possibility of a "later maturing player" increasing anthropometric (e.g., height: player 4 = 3.3 cm; player 5 = 13.2 cm; and player 6 = 15.7 cm) and fitness (e.g., 30-m sprint: player 4 = -0.18 s, player 5 = -0.46 s, and player 6 = -0.59 s) characteristics compared with early maturing players was confirmed. Findings affirm the potential for variable and changing trajectories in adolescent athletes. Practical implications advocate a long-term inclusive tracking approach of athletes, the avoidance of (de)selection, and the reduction of a performance emphasis in adolescent stages of sport systems.

Relative age effects (RAEs)—observed inequalities in participation and attainment as a result of annual age-grouping policies in youth sport—are a common problem in many sports (e.g., soccer; see Musch & Grondin, 2001). Maturational and selection mechanisms appear Symposia S15 to account for these birth-date discrepancies; however understanding how they manifest and operate—even in physically dependent sports (e.g., Rugby League)—is not clear. The purpose of this study was to examine birth date distribution, physical maturity, height, and body mass in regionally and nationally selected UK junior Rugby League players. Between 2005 and 2007, birth date, height, sitting height, and body mass were collected and age at peak height velocity (PHV) calculated (Mirwald et al., 2002) in 12- to 16-year-old players involved in the UK’s Rugby Football League National (n = 208) and Regional (n = 473) performance pathways. Chi-square analyses identified significant uneven birth date distributions, with 54% of National (χ 2 = 107.2, p < 0.0001) and 47% of Regional players (χ 2 = 140.9, p < 0.0001) born in the first quartile (i.e., Sept to Nov) alone. Related to height, 95% of National and 92% of Regional players were taller than the age-matched 50th percentile of UK reference values. And similarly, 97% of National and 96% of Regional players were above the UK’s age-matched 50th percentile for body mass. National (13.52 ± 0.58) and Regional (13.62 ± 0.6) players’ age at PHV also occurred significantly (p < 0.0001) earlier than UK reference values (Billewicz et al., 1981) of 14.1 ± 1.0 years. Although recognizing the physical demands of Rugby league, findings suggest that talent selection is overwhelmingly biased toward the relatively older, taller, heavier, and earlier maturing youngster within an annual cohort. Thus, younger and later maturing junior rugby league players are disadvantaged in selection to the performance pathway due to a lack of physical development.

Relative Age Effects (RAEs), reflecting observed inequalities in participation and selection as a result of annual age-grouping, are a common problem in most team sports (e.g. soccer; Musch & Grondin, 2001: Developmental Review, 21, 147– 167). In junior representative Rugby League, RAEs increase with each performance level with coaches preferentially selecting taller, heavier and earlier maturing players. However, the effect of playing position on RAEs is not clear with limited data available as to whether maturational differences exist between playing positions in youth sport. Therefore the purpose of this study was to examine the RAE and maturational status amongst playing positions in high performance junior Rugby League players. With institutional ethics approval, 683 regionally (e.g. Yorkshire) selected players (Age mean 14.57, s¼0.83 years) underwent anthropometric testing between 2005 and 2007. Birth date, playing position,height, sitting height and body mass were obtained, and age at Peak Height Velocity (PHV) calculated (Mirwald et al., 2002: Medicine and Science in Sport and Exercise, 34, 689–694) for each player. Player’s birth dates were recoded by quartile (e.g. Q1¼September–November, Q2¼December–February, etc.) with playing position categorised into one of four subgroups (‘‘Outside-Backs’’, ‘‘Halves and Hookers’’, ‘‘Props’’ and ‘‘Backrowers’’). Chi square analysis identified significant uneven birth date distributions (w2¼236.36, P50.01) for all Regional players and each playing position. Odds ratio (OR) and 95% Confidence Intervals (CI) identified increased risk of selection (Q1 v Q4 OR: 13.39, 95% CI: 4.32–41.53) for the ‘‘Prop’’ position, with 82.9% of ‘‘Props’’ born in the first half of the selection year. One way analysis of variance identified significant (P50.01) differences in maturity, height and body mass between positions with ‘‘Props’’ and ‘‘Backrowers’’ significantly taller, heavier and earlier maturing than the ‘‘Outside-Backs’’ and ‘‘Halves and Hookers’’. Whilst recognising the physical demands of Rugby League, findings demonstrate that player selection at junior representative levels is significantly biased towards the relatively older player, with ‘‘Props’’ and ‘‘Backrowers’’ older, earlier maturing, taller and heavier than ‘‘Outside-Backs’’ and ‘‘Halves and Hookers’’. Thus, younger and later maturing junior players, especially ‘‘Props’’ and ‘‘Backrowers’’, may be disadvantaged in selection to Regional squads due to a lack of physical development, highlighting issues related to differences between selection for current performance and talent identification and development.

In talent identification research, most studies have taken a cross-sectional rather than longitudinal approach. However, to improve understanding of factors that contribute to expert performance players should be monitored over a prolonged period (Williams & Reilly, 2000: Journal of Sports Sciences, 18, 657–667). The purpose of this study was to identify whether anthropometric and physiological characteristics could discriminate between selection levels when measured longitudinally over a 2-year period in junior Rugby League With institutional ethics approval, 683 Regional selected players completed an anthropometric and physiological battery of tests between 2005 and 2008. Players that were retained at Regional (n=26 age mean 13.60, s=0.27 years) and National (n=13 age mean 13.54, s=0.29 years) levels for three consecutive years were used for analysis. A repeated measures ANOVA was used to examine group differences between selection level (i.e. Regional and National) together with differences in characteristics over time. Findings demonstrate that differences between sum of four skinfolds and V_ O2max, measured by the multi-stage fitness test, exist between Regionaland National retained players which are maintained over a 2-year period with National players outperforming Regional players, however, speed improves at different rates. Although further longitudinal research is required, this study demonstrates that skinfold and V_ O2max measures do discriminate between Regional and National players over a 2-year period, even though such measurements are not used as part of the selection process in junior Rugby League.

In talent identification research, most studies have taken a cross-sectional rather than longitudinal approach. However, to improve understanding of factors that contribute to expert performance players should be monitored over a prolonged period (Williams & Reilly, 2000: Journal of Sports Sciences, 18, 657–667). The purpose of this study was to identify whether anthropometric and physiological characteristics could discriminate between selection levels when measured longitudinally over a 2-year period in junior Rugby League With institutional ethics approval, 683 Regional selected players completed an anthropometric and physiological battery of tests between 2005 and 2008. Players that were retained at Regional (n=26 age mean 13.60, s=0.27 years) and National (n=13 age mean 13.54, s=0.29 years) levels for three consecutive years were used for analysis. A repeated measures ANOVA was used to examine group differences between selection level (i.e. Regional and National) together with differences in characteristics over time. Findings demonstrate that differences between sum of four skinfolds and V_ O2max, measured by the multi-stage fitness test, exist between Regionaland National retained players which are maintained over a 2-year period with National players outperforming Regional players, however, speed improves at different rates. Although further longitudinal research is required, this study demonstrates that skinfold and V_ O2max measures do discriminate between Regional and National players over a 2-year period, even though such measurements are not used as part of the selection process in junior Rugby League.

Relative age effects (RAEs), reflecting observed inequalities in participation and attainment as a result of annual age-grouping policies in youth sport, are common in most team sports. The aims of this study were to determine if and when RAEs become apparent in Rugby League, determine how influential variables (e.g., gender) lead and clarify whether player retention at junior representative levels can explain persistent RAEs. Player data were collected for the male and female community games ranging from Under 7s to Senior (N=15,060) levels, junior representative selections (i.e., Regional) and professional players (N=298). Chi-square analyses found significant (P<0.05) uneven birth date distributions beginning at the earliest stages of the game and throughout into senior professionals. In junior representative selections, 47.0% of Regional and 55.7% of National representative players were born in Quartile 1, with RAE risk increasing with performance level. Gender and nationality were also found to moderate RAE risk. When tracking representative juniors, over 50% were retained for similar competition the following season. Findings clearly demonstrate that RAEs exist throughout Rugby League with early selection, performance level and retention processes, appearing to be key contributing factors responsible for RAE persistence.

This study longitudinally evaluated whether maturation and relative age interact with time during adolescence to differentially affect the development of anthropometric and fitness characteristics in junior rugby league players. Anthropometric and fitness characteristics of 81 junior players selected into the UK Rugby Football League's talent identification and development process were assessed over three consecutive occasions (i.e., under-13s, -14s, -15s). Players were grouped and compared in relation to maturational status (i.e., early, average, late) and relative age quartile (i.e., quartile 1). Repeated measures multivariate analysis of variance identified significant (P < 0.001) overall main effects for maturation group, relative age quartile and importantly a maturation group by time interaction. Findings showed that the early-maturing group had the greatest anthropometric characteristics and medicine ball throw across the three occasions. However, the late-maturing group increased their height (early = 5.0 cm, late = 10.3 cm), medicine ball throw and 60-m sprint (early = -0.46 s, late = -0.85 s) the most throughout the 2-year period. Early (de)selection policies currently applied in talent identification and development programs are questionable when performance-related variables are tracked longitudinally. During adolescence, maturation status alongside relative age should be considered and controlled for when assessing athlete potential for future progression.

Background. In this Position Statement, the International Society of Sports Nutrition (ISSN) provides an objective and critical review of the literature pertinent to nutritional considerations for training and racing in single-stage ultra-marathon. Recommendations for Training. i) Ultra-marathon runners should aim to meet the caloric demands of training by following an individualized and periodized strategy, comprising a varied, food-first approach; ii) Athletes should plan and implement their nutrition strategy with sufficient time to permit adaptations that enhance fat oxidative capacity; iii) The evidence overwhelmingly supports the inclusion of a moderate-to-high carbohydrate diet (i.e., ~60% of energy intake, 5 – 8 g⸱kg−1·d−1) to mitigate the negative effects of chronic, training-induced glycogen depletion; iv) Limiting carbohydrate intake before selected low-intensity sessions, and/or moderating daily carbohydrate intake, may enhance mitochondrial function and fat oxidative capacity. Nevertheless, this approach may compromise performance during high-intensity efforts; v) Protein intakes of ~1.6 g·kg−1·d−1 are necessary to maintain lean mass and support recovery from training, but amounts up to 2.5 g⸱kg−1·d−1 may be warranted during demanding training when calorie requirements are greater; Recommendations for Racing. vi) To attenuate caloric deficits, runners should aim to consume 150 - 400 kcal⸱h−1 (carbohydrate, 30 – 50 g⸱h−1; protein, 5 – 10 g⸱h−1) from a variety of calorie-dense foods. Consideration must be given to food palatability, individual tolerance, and the increased preference for savory foods in longer races; vii) Fluid volumes of 450 – 750 mL⸱h−1 (~150 – 250 mL every 20 min) are recommended during racing. To minimize the likelihood of hyponatraemia, electrolytes (mainly sodium) may be needed in concentrations greater than that provided by most commercial products (i.e., >575 mg·L−1 sodium). Fluid and electrolyte requirements will be elevated when running in hot and/or humid conditions; viii) Evidence supports progressive gut-training and/or low-FODMAP diets (fermentable oligosaccharide, disaccharide, monosaccharide and polyol) to alleviate symptoms of gastrointestinal distress during racing; ix) The evidence in support of ketogenic diets and/or ketone esters to improve ultra-marathon performance is lacking, with further research warranted; x) Evidence supports the strategic use of caffeine to sustain performance in the latter stages of racing, particularly when sleep deprivation may compromise athlete safety.

This study quantified the field-based external training loads of professional rugby league players using global positioning systems technology across a playing season. Eleven professional rugby league players were monitored during all field-based training activities during the 2014 Super League season. Training sessions undertaken in preseason (n = 211 observations), early (n = 194 observations), middle (n = 171 observations) and late (n = 206 observations) phases of the in-season were averaged for each player and used in the analyses. Large reductions in external training loads between preseason and in-season periods were observed. Within season, a decrease in intensity (relative distance, absolute and relative total-HSR) with a limited change in training duration was observed. These data provide a useful reference for coaches working with similar cohorts, while future research should quantify the adequacy of the training loads reported, considering impact on performance and injury.

PURPOSE: Beneficial effects of carbohydrate (CHO) ingestion on exogenous CHO oxidation and endurance performance require a well-functioning gastrointestinal (GI) tract. However, GI complaints are common during endurance running. This study investigated the effect of a CHO solution-containing sodium alginate and pectin (hydrogel) on endurance running performance, exogenous and endogenous CHO oxidation and GI symptoms. METHODS: Eleven trained male runners, using a randomised, double-blind design, completed three 120-minute steady state runs at 68% V̇O2max, followed by a 5-km time-trial. Participants ingested 90 g·h-1 of 2:1 glucose:fructose (13C enriched) either as a CHO hydrogel, a standard CHO solution (non-hydrogel), or a CHO-free placebo during the 120 minutes. Fat oxidation, total and exogenous CHO oxidation, plasma glucose oxidation and endogenous glucose oxidation from liver and muscle glycogen were calculated using indirect calorimetry and isotope ratio mass spectrometry. GI symptoms were recorded throughout the trial. RESULTS: Time-trial performance was 7.6% and 5.6% faster after hydrogel ([minutes:seconds]19:29±2:24; p<0.001) and non-hydrogel (19:54±2:23, p=0.002), respectively, versus placebo (21:05±2:34). Time-trial performance after hydrogel was 2.1% faster (p=0.033) than non-hydrogel. Absolute and relative exogenous CHO oxidation was greater with hydrogel (68.6±10.8g, 31.9±2.7%; p=0.01) versus non-hydrogel (63.4±8.1g, 29.3±2.0%; p=0.003). Absolute and relative endogenous CHO oxidation were lower in both CHO conditions compared with placebo (p<0.001), with no difference between CHO conditions. Absolute and relative liver glucose and muscle glycogen oxidation were not different between CHO conditions. Total GI symptoms were not different between hydrogel and placebo, but GI symptoms was higher in non-hydrogel compared with placebo and hydrogel (p<0.001). CONCLUSION: Ingestion of glucose and fructose in hydrogel form during running benefited endurance performance, exogenous CHO oxidation and GI symptoms, compared with a standard CHO solution.

Purpose This study investigated the effect of small manipulations in carbohydrate (CHO) dose on exogenous and endogenous (liver and muscle) fuel selection during exercise. Method Eleven trained males cycled in a double-blind randomised order on 4 occasions at 60% V˙O2max for 3 h, followed by a 30-min time-trial whilst ingesting either 80 g h−1 or 90 g h−1 or 100 g h−1 13C-glucose-13C-fructose [2:1] or placebo. CHO doses met, were marginally lower, or above previously reported intestinal saturation for glucose–fructose (90 g h−1). Indirect calorimetry and stable mass isotope [13C] techniques were utilised to determine fuel use. Result Time-trial performance was 86.5 to 93%, ‘likely, probable’ improved with 90 g h−1 compared 80 and 100 g h−1. Exogenous CHO oxidation in the final hour was 9.8–10.0% higher with 100 g h−1 compared with 80 and 90 g h−1 (ES = 0.64–0.70, 95% CI 9.6, 1.4 to 17.7 and 8.2, 2.1 to 18.6). However, increasing CHO dose (100 g h−1) increased muscle glycogen use (101.6 ± 16.6 g, ES = 0.60, 16.1, 0.9 to 31.4) and its relative contribution to energy expenditure (5.6 ± 8.4%, ES = 0.72, 5.6, 1.5 to 9.8 g) compared with 90 g h−1. Absolute and relative muscle glycogen oxidation between 80 and 90 g h−1 were similar (ES = 0.23 and 0.38) though a small absolute (85.4 ± 29.3 g, 6.2, − 23.5 to 11.1) and relative (34.9 ± 9.1 g, − 3.5, − 9.6 to 2.6) reduction was seen in 90 g h−1 compared with 100 g h−1. Liver glycogen oxidation was not significantly different between conditions (ES < 0.42). Total fat oxidation during the 3-h ride was similar in CHO conditions (ES < 0.28) but suppressed compared with placebo (ES = 1.05–1.51). Conclusion ‘Overdosing’ intestinal transport for glucose–fructose appears to increase muscle glycogen reliance and negatively impact subsequent TT performance.

Introduction Recruitment and training is vital to maintaining the size, deployability and effectiveness of armed forces, but was threatened early in the COVID-19 pandemic. Reports suggested asymptomatic seroconversion driving SARS-CoV-2 transmission in young adults. Potential association between lower vitamin D status and increased infection risk was also highlighted. We aimed to prospectively determine seroconversion and test the hypothesis that this would vary with vitamin D supplementation in representative populations. Methods Two cohorts were recruited from Yorkshire, Northern England. Infantry recruits received daily oral vitamin D (1000 IU for four weeks, followed by 400 IU for the remaining 22 weeks of training) in institutional countermeasures to facilitate ongoing training/co-habitation. Controls were recruited from an un-supplemented University population, subject to social distancing and household restrictions. Venous blood samples (baseline and Week 16) were assayed for vitamin D and anti-SARS-CoV-2 spike glycoprotein antibodies, with additional serology (weeks 4, 9, 12) by dried blood spot. Impact of supplementation was analysed on an intention-to-treat basis in volunteers completing testing at all timepoints and remaining unvaccinated against SARS-CoV-2. Variation in seroconversion with vitamin D change was explored across, and modelled within, each population. Results In the military (n=333) and University (n=222) cohorts, seroconversion rates were 44.4% vs 25.7% (P=0.003). At week 16, military recruits showed higher vitamin D (60.5 ± 19.5 mmol.L-1 vs. 53.5 ± 22.4 mmol.L-1, p < 0.001), despite <50% supplementation adherence. A statistically significant (p=0.005) effect of negative change in vitamin D (%) on seroconversion in recruits (OR of 0.991 and 95% CI of 0.984-0.997) was not evidenced in the University cohort. Conclusion Among unvaccinated populations, SARS-CoV-2 infection of infantry recruits was not reduced by institutional countermeasures, versus civilians subject to national restrictions. Vitamin D supplementation improved serum levels, but implementation did not have a clinically meaningful impact on seroconversion during military training.

• There is a growing need to develop measures for assessing performance and health status under heat stress, as heat-related health risks increase with global warming. • The ACSM recommends that a tailored heat tolerance assessment (HTA), based upon participants’ fitness levels, should be applied for individual’s affected by heat related illness. • Aerobically-trained athletes show features of heat adaptation at baseline and, in our experience, a standardised HTA to provide robust heat stress and challenge fitter individuals is lacking. • We designed a progressive HTA to be performed in uncompensable conditions, in order to minimise differences attributable to variation in body size and increase comparability.

Acute Mountain Sickness (AMS) is a common clinical challenge at high altitude (HA). A point-of-care biochemical marker for AMS could have widespread utility. Neutrophil gelatinase-associated lipocalin (NGAL) rises in response to renal injury, inflammation and oxidative stress. We investigated whether NGAL rises with HA and if this rise was related to AMS, hypoxia or exercise. NGAL was assayed in a cohort (n = 22) undertaking 6 hours exercise at near sea-level (SL); a cohort (n = 14) during 3 hours of normobaric hypoxia (FiO2 11.6%) and on two trekking expeditions (n = 52) to over 5000 m. NGAL did not change with exercise at SL or following normobaric hypoxia. During the trekking expeditions NGAL levels (ng/ml, mean ± sd, range) rose significantly (P < 0.001) from 68 ± 14 (60-102) at 1300 m to 183 ± 107 (65-519); 143 ± 66 (60-315) and 150 ± 71 (60-357) at 3400 m, 4270 m and 5150 m respectively. At 5150 m there was a significant difference in NGAL between those with severe AMS (n = 7), mild AMS (n = 16) or no AMS (n = 23): 201 ± 34 versus 171 ± 19 versus 124 ± 12 respectively (P = 0.009 for severe versus no AMS; P = 0.026 for mild versus no AMS). In summary, NGAL rises in response to prolonged hypobaric hypoxia and demonstrates a relationship to the presence and severity of AMS.

Purpose-This study sought to explore, for the first time, the effects of repeated maximal static and dynamic apnoeic attempts on the physiological milieu by assessing cerebral, cardiac and striatal muscle stress-related biomarkers in a group of elite breath-hold divers (EBHD). Methods-Sixteen healthy males were recruited (EBHD=8; controls=8). On two separate occasions EBHD performed two sets of five repeated maximal static apnoeas (STA) or five repeated maximal dynamic apnoeas (DYN). Controls performed a static eupnoeic protocol to negate any effects of water immersion and diurnal variation on haematology (CTL). Venous blood samples were drawn at 30, 90, and 180-mins after each protocol to determine S100β, neuron-specific enolase (NSE), myoglobin and high sensitivity cardiac troponin T (hscTNT) concentrations. Results-S100β and myoglobin concentrations were elevated following both apnoeic interventions (p<0.001; p≤0.028, respectively) but not after CTL (p≥0.348). S100β increased from baseline (0.024±0.005µg/L) at 30 (STA, +149%, p<0.001; DYN, +166%, p<0.001) and 90 mins (STA, +129%, p<0.001; DYN, +132%, p=0.008) following the last apnoeic repetition. Myoglobin was higher than baseline (22.3±2.7ng/mL) at 30 (+42%, p=0.04), 90 (+64%, p<0.001) and 180 mins (+49%, p=0.013) post-STA and at 90 mins (+63%, p=0.016) post-DYN. Post-apnoeic S100β and myoglobin concentrations were higher than CTL (STA, p<0.001; DYN, p≤0.004). NSE and hscTNT did not change from basal concentrations after the apnoeic (p≥0.146) nor following the eupnoeic (p≥0.553) intervention. from basal concentrations after the apnoeic (p≥0.146) nor following the eupnoeic (p≥0.553) intervention. Conclusions-This study suggests that a series of repeated maximal static and dynamic apnoeas transiently disrupt the blood-brain barrier and instigate muscle injury but do not induce neuronal-parenchymal damage or myocardial damage.

This study investigated how exercise and heat stress may affect the neurobiomarkers Glial fibrillary acid protein (GFAP) and ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCHL1). Both are assayed in plasma by a semiquantitative cartridge-based system (Abbott iSTAT Alinity®) that is FDA-approved to ‘rule in’ mild Traumatic Brain Injury (mTBI) following head trauma. We hypothesised that healthy volunteers would show unchanging levels across exercise bouts differing by mode, duration, environmental conditions and heat acclimation (HA) status. We further investigated the frequency with which the manufacturer’s decision thresholds for suspecting more severe brain injury might be breached by neurobiomarker response to exercise-heat stress. Twenty endurance trained volunteers (five females, 15 males; age 30 ± 7 years, VO2max 56 ± 10 ml.kg.min-1) were sampled for blood before and after cycle ergometry in a heated chamber (45 min at 2.0 to 2.5 W.kg-1 in 32°C), at un-adapted baseline and again following eight days of HA or control activity (combined exercise-hot water immersion regimen, n=10 vs. matched temperate exercise, n=10). Separately, 50 unacclimatised runners (nine females, 39 males; age 31 ± 5 years) gave blood at rested baseline and after running the Brighton marathon 2022 (finishing time 3 h 59 min ± 49 min; peak ambient temperature 11 °C). In each study, body core temperature (Tc) was recorded (rectal thermistor vs BodyCap® telemetry pill), change in body mass (BM) was measured and blood collected and centrifuged within 30 min post-exposure. A single accredited laboratory received frozen samples for analysis of thawed plasma by both benchtop ELISA (BENCH) and iSTAT Alinity (CARTRIDGE). Cycling in the heat resulted in significant (P<0.05) overall ΔBM (–1.41 ± 0.39 kg) and ΔTc (+1.5 ± 0.4 °C). No change in neurobiomarkers was observed by BENCH or CARTRIDGE, neither did HA status influence levels (P=0.94) despite reduced Tc and increased sweat losses. CARTRIDGE decision thresholds for GFAP (30 pg.mL-1) and UCHL1 (360 30 pg.mL-1) were not exceeded. In the marathon, significant ΔBM (-1.39 ± 1.72 kg) and ΔTc (+1.8 ± 0.6 °C) were observed. Versus baseline, GFAP did not vary, whereas UCH-L1 increased for both BENCH (64.9 [39.1, 578.1] vs 91.0 [39.1, 570.0] pg.mL-1, P=0.0018) and CARTRIDGE (200 [200, 200] vs 448 [302.8, 756.0 pg.mL-1, P<0.0001). The CARTRIDGE decision threshold was not breached for GFAP, but was exceeded for UCHL1 in 32/50 runners (highest value 2261 pg.mL-1, reportable range 200 to 3200 pg.mL-1). In summary, neurobiomarkers used in mTBI assessment were unaffected by moderate intensity and duration cycling in the heat, with HA status having no discernible impact. However, prolonged running in cool weather conditions elevated UCHL1 above the decision threshold used in mTBI assessment. These results suggest caution in interpreting elevated UCHL1 after prolonged exercise.

Introduction. Aldosterone decreases at high altitude (HA) but the effect of hypoxia on angiotensin converting-enzyme (ACE), a key step in the renin-angiotensin-aldosterone system, is unclear. Materials and Methods. We investigated the effects of exercise and acute normobaric hypoxia (NH, ~11.0% FiO2) on nine participants and six controls undertaking the same exercise at sea-level (SL). NH exposure lasted 5 hours with 90 min of submaximal treadmill walking. Blood samples for aldosterone, ACE and cortisol were taken throughout exposure and at rest during a trek to HA (5140 m) in eight separate participants. Results. There was no difference in cortisol or aldosterone between groups pre-exercise. Aldosterone rose with exercise to a greater extent at SL than in NH (post-exercise: 700±325 vs 335±238 pmol/L, mean ± SD, p=0.044). Conversely, cortisol rose to a greater extent in NH (post-exercise: 734±165 vs 344±159 nmol/L, mean ± SD, p=0.001). There were no differences in ACE activity. During the trek to HA resting aldosterone and cortisol reduced with no change in ACE. Conclusion. Acute NH subdues the exercise-associated rise in aldosterone but stimulates cortisol, whereas prolonged exposure at HA reduces both resting aldosterone and cortisol. As ACE activity was unchanged in both environments this is not the mechanism underlying the fall in aldosterone.

Introduction: The British Service Dhaulagiri Research Expedition (BSDMRE) took place from 27th March to 31st May 2016. The expedition involved 129 personnel, with voluntary participation in 9 different study protocols. Studies were conducted in three research camps established at 3600m, 4600m and 5140m and involved taking and storing blood samples, cardiac echocardiography and investigations involving a balance plate. Research in this remote environment requires careful planning in order to provide a robust and resilient power plan. In this paper we aim to report the rationale for the choices we made in terms of power supply, the equipment used and potential military applicability. Methods: This is a descriptive account from the expedition members involved in planning and conducting the medical research. Results: Power calculations were used to determine estimates of requirement prior to the expedition. The primary sources used to generate power were internal combustion engine (via petrol fueled electric generators), and solar panels. Having been generated, power was stored using lithium-ion batteries. Special consideration was given to the storage of samples taken in the field, for which electric freezers and dry-shippers were used. All equipment used functioned well during the expedition, with the challenges of altitude, temperature, and transport all overcome due to extensive prior planning. Conclusions: Power was successfully generated, stored, and delivered during the BSDMRE, allowing extensive medical research to be undertaken. The challenges faced and overcome are directly applicable to delivering military medical care in austere environments, and lessons learned can help with the planning and delivery of future operations, training exercises, or expeditions.

Purpose The aim of the study was to provide an evaluation of the oxygen transport, exchange and storage capacity of elite breath-hold divers (EBHD) compared with non-divers (ND). Methods Twenty-one healthy males’ (11 EBHD; 10 ND) resting splenic volumes were assessed by ultrasound and venous blood drawn for full blood count analysis. Percutaneous skeletal muscle biopsies were obtained from the m. vastus lateralis to measure capillarisation, and fibre type-specific localisation and distribution of myoglobin and mitochondrial content using quantitative immunofluorescence microscopy. Results Splenic volume was not different between groups. Reticulocytes, red blood cells and haemoglobin concentrations were higher (+ 24%, p < 0.05; + 9%, p < 0.05; + 3%, p < 0.05; respectively) and mean cell volume was lower (− 6.5%, p < 0.05) in the EBHD compared with ND. Haematocrit was not different between groups. Capillary density was greater (+ 19%; p < 0.05) in the EBHD. The diffusion distance (R95) was lower in type I versus type II fibres for both groups (EBHD, p < 0.01; ND, p < 0.001), with a lower R95 for type I fibres in the EBHD versus ND (− 13%, p < 0.05). Myoglobin content was higher in type I than type II fibres in EBHD (+ 27%; p < 0.01) and higher in the type I fibres of EBHD than ND (+ 27%; p < 0.05). No fibre type differences in myoglobin content were observed in ND. Mitochondrial content was higher in type I than type II fibres in EBHD (+ 35%; p < 0.05), with no fibre type differences in ND or between groups. Conclusions In conclusion, EBDH demonstrate enhanced oxygen storage in both blood and skeletal muscle and a more efficient oxygen exchange capacity between blood and skeletal muscle versus ND.

Serum erythropoietin (EPO) concentration is increased following static apnoea-induced hypoxia. However, the acute erythropoietic responses to a series of dynamic apnoeas in non-divers (ND) or elite breath-hold divers (EBHD) are unknown. Participants were stratified into EBHD (n=8), ND (n=10) and control (n=8) groups. On two separate occasions EBHD and ND performed a series of five maximal dynamic apnoeas (DYN) or two sets of five maximal static apnoeas (STA). Control performed a static eupnoeic (STE) protocol to control against any effects of water immersion and diurnal variation on EPO. Peripheral oxygen saturation (SpO2) levels were monitored up to 20s post each maximal effort. Blood samples were collected at 30, 90, and 180-min after each protocol for EPO, haemoglobin and haematocrit concentrations. No between group differences were observed at baseline (p>0.05). For EBHD and ND, mean end-apnoea SpO2 was lower in DYN (EBHD,62±10%,p=0.024;ND,85±6%;p=0.020) than STA (EBHD,76±7%;ND,96±1%) and control (98±1%) protocols. EBHD attained lower end-apnoeic SpO2 during DYN and STA than ND (p<0.001). Serum EPO increased from baseline following the DYN protocol in EBHD only (EBHD,p<0.001;ND,p=0.622). EBHD EPO increased from baseline (6.85±0.9mlU/mL) by 60% at 30-min (10.82±2.5mlU/mL,p=0.017) and 63% at 180-min (10.87±2.1mlU/mL,p=0.024). Serum EPO did not change after the STA (EBHD,p=0.534;ND,p=0.850) and STE (p=0.056) protocols. There was a significant negative correlation (r=-0.49,p=0.003) between end-apnoeic SpO2 and peak post-apnoeic serum EPO concentrations. The novel findings demonstrate that circulating EPO is only increased after DYN in EBHD. This may relate to the greater hypoxemia achieved by EBHD during the DYN.

Splenic contractions occur in response to apnoea‐induced hypoxia with and without facial water immersion. However, the splenic responses to a series of static (STA) or dynamic (DYN) apnoeas with whole‐body water immersion in non‐divers (NDs) and elite breath‐hold divers (EBHDs) are unknown. EBHD (n = 8), ND (n = 10) and control participants (n = 8) were recruited. EBHD and ND performed a series of five maximal DYN or STA on separate occasions. Control performed a static eupnoeic (STE) protocol to control against any effects of water immersion and diurnal variation on splenic volume and haematology. Heart rate (HR) and peripheral oxygen saturation (SpO2) were monitored for 30 s after each apnoea. Pre‐ and post‐apnoeic splenic volumes were quantified ultrasonically, and blood samples were drawn for haematology. For EBHD and ND end‐apnoeic HR was higher (P < 0.001) and SpO2 was lower in DYN (P = 0.024) versus STA. EBHD attained lower end‐apnoeic SpO2 during DYN and STA than NDs (P < 0.001). Splenic contractions occurred following DYN (EBHD, −47 ± 6%; ND, −37 ± 4%; P < 0.001) and STA (EBHD, −26 ± 4%; ND, −26 ± 8%; P < 0.01). DYN‐associated splenic contractions were greater than STA in EBHD only (P = 0.042). Haemoglobin concentrations were higher following DYN only (EBHD, +5 ± 8g/L , +4 ± 2%; ND, +8 ± 3 g/L , +4.9 ± 3%; P = 0.019). Haematocrit remained unchanged after each protocol. There were no between group differences in post‐apnoeic splenic volume or haematology. In both groups, splenic contractions occurred in response to STA and DYN when combined with whole‐body immersion. DYN apnoeas, were effective at increasing haemoglobin concentrations but not STA apnoeas. Thus, the magnitude of the splenic response relates to the hypoxemic stress encountered during apnoeic epochs.

Background and Objectives: Neurobiomarkers measured in peripheral blood can supplement management strategies following traumatic brain injury (TBI). Dual-assay of glial fibrillary acid protein (GFAP) and ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCHL1) is FDA-approved to inform a decision threshold approach (GFAP >30 μg.L-1 and/or UCHL1 >360 μg.L-1) for post-TBI neuroimaging. As physical activity and thermal strain often accompany TBI-prone activities, we investigated whether each molecule’s quantification - and, by extension, clinical decisions - could be influenced by exercise-heat stress. Methods: In healthy volunteers monitored continuously for body core temperature (Tc), we used the i-STAT Alinity to assess plasma GFAP and UCHL1 responses to exercise in the laboratory (four female, eighteen male trained participants, cycling for 45 min in 32 °C) and field (three female and 22 male recreational marathon runners, finishing time 231± 34 min, peak ambient temperature 11 °C). Results: Respective ΔTc overall were 1.42 ± 0.37 °C and 1.87 [1.53, 2.31] °C. With laboratory exercise, GFAP and UCHL1 did not exceed the manufacturer’s decision threshold. Across the marathon, GFAP was stable, whereas UCH-L1 more than doubled (200 [200, 200] vs 462 [310, 782] μg.L-1, P<0.0001), breaching the decision threshold for neuroimaging in 18/25 runners. Discussion: Confounding from more severe exercise-heat stress should be considered when interpreting near-care assay of UCHL1 for TBI management.

This study evaluated the effects of inspiratory muscle training (IMT) on inspiratory muscle fatigue (IMF) and physiological and perceptual responses during trekking-specific exercise. An 8-week IMT program was completed by 21 males (age 32.4 ± 9.61 years, VO2peak 58.8 ± 6.75 mL/kg/min) randomised within matched pairs to either the IMT group (n = 11) or the placebo group [(P), n = 9]. Twice daily, participants completed 30 (IMT) or 60 (P) inspiratory efforts using a Powerbreathe initially set at a resistance of 50% (IMT) or used at 15% (P) of maximal inspiratory pressure (MIP) throughout. A loaded (12.5 kg) 39-minute incremental walking protocol (3–5 km/hour and 1–15% gradient) was completed in normobaric hypoxia (PIO2 = 110 mmHg, 3000 m) before and after training. MIP increased from 164 to 188 cmH2O (18%) and from 161 to 171 cmH2O (6%) in the IMT and P groups (P = 0.02). The 95% CI for IMT showed a significant improvement in MIP (5.21±43.33 cmH2O), but not for P. IMF during exercise (MIP) was*5%, showing no training effect for either IMT or P (P = 0.23). Rating of perceived exertion (RPE) was consistently reduced (*1) throughout exercise following training for IMT, but not for P (P = 0.03). The mean blood lactate concentration during exercise was significantly reduced by 0.26 and 0.15 mmol/L in IMT and P (P = 0.00), with no differences between groups (P = 0.34). Rating of dyspnoea during exercise decreased (*0.4) following IMT but increased (*0.3) following P (P = 0.01). IMT may attenuate the increased physiological and perceived exercise stress experienced during normobaric hypoxia, which may benefit moderate altitude expeditions

The effects of inspiratory muscle training (IMT) were evaluated at rest and during exercise in normobaric hypoxia (NH) and then an 11-day trek to 5300m. A 7-week IMT program was completed by 6 females and 3 males (age 34.8 ± 10.0 years) randomized to IMT (n = 4) or placebo [P (n = 5)]. A Powerbreathe was initially set at a resistance of 50% (IMT) or used at 15%ofmaximal inspiratory pressure (MIP) throughout (P). A self-paced walking test was completed before and after training at PIO2 = 104.1mmHg, 3440m (NH1); PIO2 = 85.9 mmHg, 4930m (NH2); and at 3440m during the trek (HH). Exercise data were interpolated to 4.8 km/hour to evaluate training effects. Patterns of change suggest possible benefits of IMT, but due to small group sizes and variability, these trends are not significant. MIP increased by 6% and 4% following IMT and P. Pulse oxygen saturation (SaO2) during exercise in NH2 increased by*4% following IMT, with no change in P. Decreases in resting SaO2 during the expedition (4930m) were attenuated in IMT (85.0 ± 3.61%) compared to P (80.0 ± 5.87%). Comparisons between NH1 exercise post-training and HH showed a decrease in perceived dyspnoea and effort in IMT ( - 0.3 and - 0.7) but an increase in P ( + 0.7 and + 2.6). Nonsignificant trends within the data suggest that the altitude-induced decrease in resting and exercise SaO2 and intensified perceived effort and dyspnoea during exercise were attenuated following IMT. However, further research is required to establish any beneficial effect of IMT.

BACKGROUND: A recent commentary has been published on our meta-analysis, which investigated substrate oxidation during exercise matched for relative intensities in hypoxia compared with normoxia. Within this commentary, the authors proposed that exercise matched for absolute intensities in hypoxia compared with normoxia, should have been included within the analysis, as this model provides a more suitable experimental design when considering nutritional interventions in hypoxia. MAIN BODY: Within this response, we provide a rationale for the use of exercise matched for relative intensities in hypoxia compared with normoxia. Specifically, we argue that this model provides a physiological stimulus replicable of real world situations, by reducing the absolute workload undertaken in hypoxia. Further, the use of exercise matched for relative intensities isolates the metabolic response to hypoxia, rather than the increased relative exercise intensity experienced in hypoxia when utilising exercise matched for absolute intensities. In addition, we also report previously unpublished data analysed at the time of the original meta-analysis, assessing substrate oxidation during exercise matched for absolute intensities in hypoxia compared with normoxia. CONCLUSION: An increased reliance on carbohydrate oxidation was observed during exercise matched for absolute intensities in hypoxia compared with normoxia. These data now provide a comparable dataset for the use of researchers and practitioners alike in the design of nutritional interventions for relevant populations.

Introduction The hypoxic exposure experienced at altitude is known to impair endurance performance, which may in part be related to changes in substrate utilisation. However, equivocal findings have been reported regarding the contribution of carbohydrate and fat to the total energy yield in hypoxia. These divergent findings may be due to differences in methodological design, such as the nutritional status of participants prior to exercise. As such, this study was the first to investigate the effect of the fasted and fed state on substrate utilisation during exercise in normoxia and normobaric hypoxia. Methods Twelve men rested and performed exercise twice in sea level (SL) conditions (~20.93% O2) and twice at normobaric hypoxia (NH) equivalent to 4300m (Fi02~11.7%) in a randomised, crossover design. Participants entered the chamber after an overnight fast. After 1 hour, one trial within each experimental condition remained fasted, while the other included consumption of a high carbohydrate breakfast (567 kcal, 68% carbohydrate, 12% fat, 20% protein). One hour after consumption of breakfast (fed trials) or no breakfast (fasted trials), participants walked for one hour at intensities of 40%, 50% and 60% of altitude specific VO2max. Walking was performed on a treadmill at 10-15% gradient whilst carrying a 10kg backpack to simulate altitude trekking. Expired gas was measured throughout, using online gas analysis for the quantification of carbohydrate and fat oxidation. Results Relative carbohydrate oxidation was significantly reduced in NH fasted conditions compared with SL fasted conditions at 40% (SL fasted: 38.5±15.5%; NH fasted: 22.4±17.5%; p = 0.03) and 60% VO2max (SL fasted: 50.1±17.6%; NH fasted: 35.4±12.4%; p = 0.03), with a trend observed at 50% VO2max (SL fasted: 38.0±17.0%; NH fasted: 23.6±17.9%; p = 0.07). Relative fat oxidation in the fasted state was reciprocal to the fasted relative carbohydrate findings at all intensities. No significant differences in relative carbohydrate oxidation were observed in NH fed conditions compared with SL fed conditions at 40% (SL fed: 48.5±13.3%; NH fed: 44.1±20.6%; p = 0.99), 50% (SL fed: 47.1±14.0%; NH fed: 43.1±11.7%; p = 0.99) and 60% VO2max (SL fed: 55.1±15.0%; NH fed: 54.6±17.8%; p = 0.99). Relative fat oxidation in the fed state was reciprocal to the fed relative carbohydrate findings at all intensities. Conclusion This study is the first to establish that relative carbohydrate contributions to energy expenditure decrease, while relative fat contributions increase, during exercise matched for relative intensities in NH compared with SL when in the fasted, but not fed state. These findings suggest that the feeding state of participants may explain some of the divergence within the current literature regarding the effects of hypoxia on substrate utilisation. Further, these findings should be considered when prescribing nutritional support for mountaineers and military personnel trekking at high altitude.

Purpose: Reported substrate oxidation responses in hypoxia are divergent, and may be due to differences in methodological design, such as pre-exercise nutritional status and exercise intensity. This study investigated the effect of breakfast consumption versus omission on substrate oxidation at varying exercise intensities in normobaric hypoxia compared with normoxia. Methods: Twelve participants rested and exercised once after breakfast consumption and once after omission in normobaric hypoxia (4300 m: FiO2 ~11.7%) and normoxia. Exercise consisted of walking for 20-minutes at 40%, 50% and 60% of altitude-specific V̇O2max at 10-15% gradient with a 10 kg backpack. Indirect calorimetry was used to calculate carbohydrate and fat oxidation. Results: The relative contribution of carbohydrate oxidation to energy expenditure was significantly reduced in hypoxia compared with normoxia during exercise after breakfast omission at 40% (22.4 ± 17.5% vs. 38.5±15.5%, p = 0.03) and 60% V̇O2max (35.4±12.4 vs. 50.1±17.6%, p = 0.03), with a trend observed at 50% V̇O2max (23.6±17.9% vs. 38.1± 17.0%, p = 0.07). The relative contribution of carbohydrate oxidation to energy expenditure was not significantly different in hypoxia compared with normoxia during exercise after breakfast consumption at 40% (42.4±15.7% vs. 48.5±13.3%, p = 0.99), 50% (43.1±11.7% vs. 47.1±14.0%, p = 0.99) and 60% V̇O2max (54.6±17.8% vs. 55.1±15.0%, p = 0.99). Conclusions: Relative carbohydrate oxidation was significantly reduced in hypoxia compared with normoxia during exercise after breakfast omission but not during exercise after breakfast consumption. This response remained consistent with increasing exercise intensities. These findings may explain some of the disparity in the literature

Purpose: The purpose of experiment one was to determine the appetite, acylated ghrelin and energy intake response to breakfast consumption and omission in hypoxia and normoxia. Experiment two aimed to determine the appetite, acylated ghrelin and energy intake response to carbohydrate supplementation after both breakfast consumption and omission in hypoxia. Methods: In experiment one, twelve participants rested and exercised once after breakfast consumption and once after omission in normobaric hypoxia (4300 m: FiO2 ~11.7%) and normoxia. In experiment two, eleven participants rested and exercised in normobaric hypoxia (4300 m: FiO2 ~11.7%), twice after consuming a high carbohydrate breakfast and twice after breakfast omission. Participants consumed both a carbohydrate (1.2g·min

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Background Participation in sport is a popular pastime for children and adolescents that improves their physical health, mental health and motor skills. Musculoskeletal injuries are a relatively common downside of sports participation and can have negative long-term consequences. Injury prevention programmes have demonstrated effectiveness in child and adolescent sports, provided compliance is adequate. However, little is known about the factors which relate to their impact on the wider community and whether the prevention programmes have been adopted and maintained in the long-term. The objective of this review was to assess the current literature on exercise-based injury prevention interventions in child and adolescent sports (aged under 19 years) against the ‘Reach’, ‘Effectiveness’, ‘Adoption’, ‘Implementation’, ‘Maintenance’ (RE-AIM) framework and Consensus of Exercise Reporting Template (CERT), to ascertain level of reporting for the components which relate to external validity. Methods Seven electronic databases; PubMed, Medline, SPORTDiscus, PsycINFO, CINAHL, Scopus and The Cochrane Library, were searched from date of inception to July 2022 using the themes of: ‘Child and Adolescent’, ‘Sport’, ‘Injury’ and ‘Prevention’. Eligibility criteria included: Experimental trial design, exercise-based intervention programmes, primary outcome of injury incidence and participants aged under 19 years. Two reviewers assessed each trial independently against the RE-AIM model dimension items checklist (RE-AIM MDIC) and Consensus on Exercise Reporting Template (CERT) before reaching a consensus on reporting. Results Forty-five unique trials met the eligibility criteria. Mean reporting level for all studies across the whole RE-AIM MDIC was 31% (SD ± 16.2%, Range 7–77%). The domain of ‘effectiveness’ was the most comprehensively reported (60%), followed by ‘implementation’ (48%), ‘reach’ (38%), ‘adoption’ (26%) and ‘maintenance’ (7%). The mean reporting score for the CERT was 50% (SD ± 20.8, range 0–81%). Conclusion Published data on injury prevention in child and adolescent sports is highly focussed on the effectiveness of the intervention, with little consideration given to how it will be adopted and maintained in the long-term. This has led to considerable gaps in knowledge regarding optimal programme implementation, with a lack of data on adoption and maintenance contributing to the gap between research and practice. Future research needs to place greater focus on external validity and consider incorporating the study of implementation and feasibility as part of effectiveness trial design. This approach should provide the data that will help narrow the considerable gap between science and practice.

This study evaluated the effects of inspiratory muscle training (IMT) on inspiratory muscle fatigue (IMF) and physiological and perceptual responses during trekking-specific exercise. An 8-week IMT program was completed by 21 males (age 32.4 – 9.61 years, VO2peak 58.8 – 6.75 mL/kg/min) randomised within matched pairs to either the IMT group (n = 11) or the placebo group [(P), n = 9]. Twice daily, participants completed 30 (IMT) or 60 (P) inspiratory efforts using a Powerbreathe initially set at a resistance of 50% (IMT) or used at 15% (P) of maximal inspiratory pressure (MIP) throughout. A loaded (12.5 kg) 39-minute incremental walking protocol (3–5 km/hour and 1–15% gradient) was completed in normobaric hypoxia (PIO2 = 110 mmHg, 3000 m) before and after training. MIP increased from 164 to 188 cmH2O (18%) and from 161 to 171 cmH2O (6%) in the IMT and P groups (P = 0.02). The 95% CI for IMT showed a significant improvement in MIP (5.21–43.33 cmH2O), but not for P. IMF during exercise (MIP) was ~5%, showing no training effect for either IMT or P (P = 0.23). Rating of perceived exertion (RPE) was consistently reduced (~1) throughout exercise following training for IMT, but not for P (P = 0.03). The mean blood lactate concentration during exercise was significantly reduced by 0.26 and 0.15 mmol/L in IMT and P (P = 0.00), with no differences between groups (P = 0.34). Rating of dyspnea during exercise decreased (~0.4) following IMT but increased (~0.3) following P (P = 0.01). IMT may attenuate the increased physiological and perceived exercise stress experienced during normobaric hypoxia, which may benefit moderate altitude expeditions.

The effects of inspiratory muscle training (IMT) were evaluated at rest and during exercise in normobaric hypoxia (NH) and then an 11-day trek to 5300m. A 7-week IMT program was completed by 6 females and 3 males (age 34.8 ± 10.0 years) randomized to IMT (n = 4) or placebo [P (n = 5)]. A Powerbreathe was initially set at a resistance of 50% (IMT) or used at 15% of maximal inspiratory pressure (MIP) throughout (P). A self-paced walking test was completed before and after training at PIO2 = 104.1mmHg, 3440m (NH1); PIO2 = 85.9 mmHg, 4930m (NH2); and at 3440m during the trek (HH). Exercise data were interpolated to 4.8 km/hour to evaluate training effects. Patterns of change suggest possible benefits of IMT, but due to small group sizes and variability, these trends are not significant. MIP increased by 6% and 4% following IMT and P. Pulse oxygen saturation (SaO2) during exercise in NH2 increased by*4% following IMT, with no change in P. Decreases in resting SaO2 during the expedition (4930m) were attenuated in IMT (85.0 ± 3.61%) compared to P (80.0 ± 5.87%). Comparisons between NH1 exercise post-training and HH showed a decrease in perceived dyspnoea and effort in IMT ( - 0.3 and - 0.7) but an increase in P ( + 0.7 and + 2.6). Nonsignificant trends within the data suggest that the altitude-induced decrease in resting and exercise SaO2 and intensified perceived effort and dyspnoea during exercise were attenuated following IMT. However, further research is required to establish any beneficial effect of IMT.

There has been considerable debate as to whether different modalities of simulated hypoxia induce similar cardiac responses.This was a prospective observational study of 14 healthy subjects aged 22-35 years. Echocardiography was performed at rest and at 15 and 120 minutes following two hours exercise under normobaric normoxia (NN) and under similar PiO2 following genuine high altitude (GHA) at 3,375m, normobaric hypoxia (NH) and hypobaric hypoxia (HH) to simulate the equivalent hypoxic stimulus to GHA.All 14 subjects completed the experiment at GHA, 11 at NN, 12 under NH, and 6 under HH. The four groups were similar in age, sex and baseline demographics. At baseline rest right ventricular (RV) systolic pressure (RVSP, p = 0.0002), pulmonary vascular resistance (p = 0.0002) and acute mountain sickness (AMS) scores were higher and the SpO2 lower (p<0.0001) among all three hypoxic groups (GHA, NH and HH) compared with NN. At both 15 minutes and 120 minutes post exercise, AMS scores, Cardiac output, septal S', lateral S', tricuspid S' and A' velocities and RVSP were higher and SpO2 lower with all forms of hypoxia compared with NN. On post-test analysis, among the three hypoxia groups, SpO2 was lower at baseline and 15 minutes post exercise with GHA (89.3±3.4% and 89.3±2.2%) and HH (89.0±3.1 and (89.8±5.0) compared with NH (92.9±1.7 and 93.6±2.5%). The RV Myocardial Performance (Tei) Index and RVSP were significantly higher with HH than NH at 15 and 120 minutes post exercise respectively and tricuspid A' was higher with GHA compared with NH at 15 minutes post exercise.GHA, NH and HH produce similar cardiac adaptations over short duration rest despite lower SpO2 levels with GHA and HH compared with NH. Notable differences emerge following exercise in SpO2, RVSP and RV cardiac function.

Mouth-rinsing with carbohydrate solutions during cycling time trials results in performance enhancements, however the majority of studies have utilised ∼6% carbohydrate solutions. Therefore, the purpose of this study was to compare the effectiveness of mouth-rinsing with 4%, 6%, and 8% carbohydrate (CHO) solutions on 1-h simulated cycling time trial performance. On four occasions, seven trained male cyclists completed at the postprandial period, a set amount of work as fast as possible in a randomised, counterbalanced order. The subjects mouth rinsed for 5-s, upon completion of each 12.5% of the trial, with 25 mL of a non-CHO placebo, 4%, 6%, and 8% CHO solutions. No additional fluids were consumed during the time trial. Heart rate (HR), ratings of perceived exertion (RPE), thirst (TH) and subjective feelings (SF) were recorded after each rinse. Further, blood samples were drawn every 25% of the trial to measure blood glucose (BG) and blood lactate (BG) concentrations, whilst whole body carbohydrate oxidation was monitored continuously. Time to completion was not significant between conditions with the placebo, 4%, 6%, and 8% conditions completing the trials in 62.0 ± 3.0, 62.8 ± 4.0, 63.4 ± 3.4, and 63 ±4.0 minutes respectively. There were no significant differences between conditions in any of the variables mentioned above however significant time effects were observed for HR, RPE, TH, and SF. Post-hoc analysis showed that TH and SF of subjects in the CHO conditions but not in the placebo were significantly increased by completion of the time trial. In conclusion, mouth-rinsing with CHO solutions did not impact 1-h cycling performance in the postprandial period and in the absence of fluid intake. Our findings suggest that there is scope for further research to explore the activation regions of the brain and whether they are receptive to CHO dose, before specific recommendations for athletic populations are established. Consequently mouth-rinsing as a practical strategy for coaches and athletes is questionable under specific conditions and should be carefully considered before its inclusion. The emphasis should be focused on appropriate dietary and fluid strategies during training and competition.

Background Detecting antibody responses following infection with SARS-CoV-2 is necessary for sero-epidemiological studies and assessing the role of specific antibodies in disease, but serum or plasma sampling is not always viable due to logistical challenges. Dried blood spot sampling (DBS) is a cheaper, simpler alternative and samples can be self-collected and returned by post, reducing risk for SARS-CoV-2 exposure from direct patient contact. The value of large-scale DBS sampling for the assessment of serological responses to SARS-CoV-2 has not been assessed in depth and provides a model for examining the logistics of using this approach to other infectious diseases. The ability to measure specific antigens is attractive for remote outbreak situations where testing may be limited or for patients who require sampling after remote consultation. Methods We compared the performance of SARS-CoV-2 anti-spike and anti-nucleocapsid antibody detection from DBS samples with matched serum collected by venepuncture in a large population of asymptomatic young adults (N = 1070) living and working in congregate settings (military recruits, N = 625); university students, N = 445). We also compared the effect of self-sampling (ssDBS) with investigator-collected samples (labDBS) on assay performance, and the quantitative measurement of total IgA, IgG and IgM between DBS eluates and serum. Results Baseline seropositivity for anti-spike IgGAM antibody was significantly higher among university students than military recruits. Strong correlations were observed between matched DBS and serum samples in both university students and recruits for the anti-spike IgGAM assay. Minimal differences were found in results by ssDBS and labDBS and serum by Bland Altman and Cohen kappa analyses. LabDBS achieved 82.0% sensitivity and 98.2% specificity and ssDBS samples 86.1% sensitivity and 96.7% specificity for detecting anti-spike IgGAM antibodies relative to serum samples. For anti-SARS-CoV-2 nucleocapsid IgG there was qualitatively 100% agreement between serum and DBS samples and weak correlation in ratio measurements. Strong correlations were observed between serum and DBS-derived total IgG, IgA, and IgM. Conclusions This is the largest validation of DBS against paired serum for SARS-CoV-2 specific antibody measurement and we have shown that DBS retains performance from prior smaller studies. There were no significant differences regarding DBS collection methods, suggesting that self-collected samples are a viable sampling collection method. These data offer confidence that DBS can be employed more widely as an alternative to classical serology.

The use of global positioning systems (GPS) technology within referees of any sport is limited. Therefore, the purpose of the current study was to evaluate the movement and physiological demands of professional rugby league referees using GPS tracking analysis. Time-motion analysis was undertaken on 8 referees using 5-Hz GPS devices and heart rate monitors throughout a series of Super League matches. 44 data sets were obtained with results identifying similar total distance covered between first and second half periods with a significant (P=0.004) reduction in the number of high velocity efforts performed between 5.51-7.0 m.s-1 (1st=21±8, 2nd=18±8). Mean distance covered from greatest to least distance, was 3 717±432 m, 3 009±402 m, 1 411±231 m, 395±133 m and 120±97 m for the following 5 absolute velocity classifications, respectively; 0.51-2.0 m.s-1; 2.1-4.0 m.s-1: 4.01-5.5 m.s-1; 5.51-7.0 m.s-1; <7.01 m.s-1. Heart rate was significantly (P<0.001) greater in the first (85.5±3.4% maxHR) compared to the second (82.9±3.8% maxHR) half. This highlights the intermittent nature of rugby league refereeing, consisting of low velocity activity interspersed with high velocity efforts and frequent changes of velocity. Training should incorporate interval training interspersing high velocity efforts of varying distances with low velocity activity while trying to achieve average heart rates of ~ 84% maxHR to replicate the physiological demands.

Research examining the factors influencing selection within talented junior Rugby League players is limited. The aims of this study were firstly to determine whether differences existed for anthropometric and performance characteristics between regional and national selection in high performance UK junior Rugby League players, and secondly to identify variables that discriminated between these selection levels. Regional representative (n=1172) selected junior players (aged 13-16 years) undertook an anthropometric and fitness testing battery with players split according to selection level (i.e., national, regional). MANCOVA analyses, with age and maturation controlled, identified national players as having lower sum of 4 skinfolds scores compared to regional players, and also performed significantly better on all physical tests. Stepwise discriminant analysis identified that estimated maximum oxygen uptake (VO2max), chronological age, body mass, 20 m sprint, height, sum of 4 skinfolds and sitting height discriminated between selection levels, accounting for 28.7% of the variance. This discriminant analysis corresponded to an overall predictive accuracy of 63.3% for all players. These results indicate that performance characteristics differed between selection levels in junior Rugby League players. However, the small magnitude of difference between selection levels suggests that physical qualities only partially explain higher representative selection. The monitoring and evaluation of such variables, alongside game related performance characteristics, provides greater knowledge and understanding about the processes and consequences of selection, training and performance in youth sport.

Fluid and sodium balance is important for performance and health; however, limited data in rugby union players exist. The purpose of the study was to evaluate body mass (BM) change (dehydration) and blood[Na] change during exercise. Data were collected from 10 premiership rugby union players, over a 4-week period. Observations included match play (23 subject observations), field (45 subject observations), and gym (33 subject observations) training sessions. Arrival urine samples were analyzed for osmolality, and samples during exercise were analyzed for [Na]. Body mass and blood[Na] were determined pre- and postexercise. Sweat[Na] was analyzed from sweat patches worn during exercise, and fluid intake was measured during exercise. Calculations of fluid and Na loss were made. Mean arrival urine osmolality was 423 ± 157 mOsm·kg, suggesting players were adequately hydrated. After match play, field, and gym training, BM loss was 1.0 ± 0.7, 0.3 ± 0.6, and 0.1 ± 0.6%, respectively. Fluid loss was significantly greater during match play (1.404 ± 0.977 kg) than field (1.008 ± 0.447 kg, p = 0.021) and gym training (0.639 ± 0.536 kg, p < 0.001). Fluid intake was 0.955 ± 0.562, 1.224 ± 0.601, and 0.987 ± 0.503 kg during match play, field, and gym training, respectively. On 43% of observations, players were hyponatremic when BM increased, 57% when BM was maintained, and 35% when there was a BM loss of 0.1-0.9%. Blood[Na] was the representative of normonatremia when BM loss was >1.0%. The findings demonstrate that rugby union players are adequately hydrated on arrival, fluid intake is excessive compared with fluid loss, and some players are at risk of developing hyponatremia.

The current study retrospectively investigated the differences in anthropometric and fitness characteristics of junior rugby league players selected onto a talent identification and development (TID) programme between long-term career progression levels (i.e., amateur, academy, professional).

This study evaluated the influence of annual-age category, relative age, playing position, anthropometry and fitness on the career attainment outcomes of junior rugby league players originally selected to a talent identification and development (TID) programme. Junior rugby league players (N=580) were grouped retrospectively according to their career attainment level (i.e., amateur, academy and professional). Anthropometric (height, sitting height, body mass, sum of four skinfolds), maturational (age at peak height velocity) and fitness (power, speed, change of direction speed, estimated ) characteristics were assessed at the Under 13s, 14s and 15s annual-age categories. Relative age (Q2=8.5% vs. Q4=25.5%) and playing position (Pivots=19.5% vs. Props=5.8%) influenced the percentage of players attaining professional status. Anthropometry and fitness had a significant effect on career attainment at the Under 14 (p=0.002, η2=0.16) and 15 (p=0.01, η2=0.12) annual-age categories. Findings at the Under 14s showed future professional players were significantly later maturing compared to academy and amateur players. Findings suggest that relative age, playing position, anthropometry and fitness can influence the career attainment of junior rugby league players. TID programmes within rugby league, and other related team sports, should be aware and acknowledge the factors influencing long-term career attainment, and not delimit development opportunities during early adolescence.

The purpose of this study was to assess the reliability of blood biomarkers that can signify exercise-induced heat stress in hot conditions. Fourteen males completed two heat stress tests separated by 5-7 days. Venous blood was drawn pre- and post- heat stress for the concentration of normetanephrine, metanephrine, serum osmolality, copeptin, kidney-injury molecule 1 and neutrophil gelatinase-associated lipocalin. No biomarker, except copeptin, displayed systematic trial order bias (p ≥ 0.05). Normetanephrine, copeptin and neutrophil gelatinase-associated lipocalin presented acceptable reliability (CV range: 0.9-14.3%), while greater variability was present in metanephrine, osmolality and kidney-injury molecule 1 (CV range: 28.6-43.2%). Normetanephrine exhibited the largest increase (p <0.001) in response to heat stress (trial 1 = 1048 ± 461 pmol. L-1; trial 2 = 1067 ± 408 pmol. L-1), whilst kidney-injury molecule 1 presented trivial changes (trial 1 = -4 ± 20 ng. L-1; trial 2 = 2 ± 16 ng. L-1, p >0.05). Normetanephrine, copeptin and neutrophil gelatinase-associated lipocalin demonstrated good reliability and sensitivity to an acute bout of heat stress. These biomarkers may be suitable for application in laboratory and field research to understand the efficacy of interventions that can attenuate the risk of thermal injury whilst exercising in the heat.

Heat adaption through acclimatisation or acclimation improves cardiovascular stability by maintaining cardiac output due to compensatory increases in stroke volume. The main aim of this study was to assess whether 2D transthoracic echocardiography (TTE) could be used to confirm differences in resting echocardiographic parameters, before and after active heat acclimation (HA). Thirteen male endurance trained cyclists underwent a resting blinded TTE before and after randomisation to either 5 consecutive daily exertional heat exposures of controlled hyperthermia at 32◦C with 70% relative humidity (RH) (HOT) or 5-days of exercise in temperate (21◦C with 36% RH) environmental conditions (TEMP). Measures of HA included heart rate, gastrointestinal temperature, skin temperature, sweat loss, total non-urinary fluid loss (TNUFL), plasma volume and participant’s ratings of perceived exertion (RPE). Following HA, the HOT group demonstrated increased sweat loss (p = 0.01) and TNUFL (p = 0.01) in comparison to the TEMP group with a significantly decreased RPE (p = 0.01). On TTE, post exposure, there was a significant comparative increase in the HOT group in left ventricular end diastolic volume (p = 0.029), SV (p = 0.009), left atrial volume (p = 0.005), inferior vena cava diameter (p = 0.041), and a significant difference in mean peak diastolic mitral annular velocity (e’) (p = 0.044).Cardiovascular adaptations to HA appear to be predominantly mediated by improvements in increased preload and ventricular compliance. TTE is a useful tool to demonstrate and quantify cardiac HA.

It is important to employ training practices that ensure that fire-fighter instructors work in an environment which does not provoke unacceptable rises in core temperature (>38°C). PURPOSE: To assess the effects of a two-day fire-behaviour training (FBT) course on the core temperature (Tc) of fire-fighter instructors in order to establish whether current training practices ensure a safe working environment. METHODS: Eleven males (mean±sd age 38.3±4.3 yr, body mass 88.5±12.7 kg and stature 177.8±5.3 cm) from two regional training centres completed three days of standard FBT, wearing full protective clothing and breathing apparatus. Two consecutive days (HOT1 and HOT2, mean ambient temperature of 12.7°C) each consisted of a morning and an afternoon heat exposure (approximately 30 minutes in duration). The third day was a control (NORM), without heat exposure (mean Tc of 19.3 °C). Tc was measured at baseline (BASE) and at the start and end of the two exposures (PRE-AM, POST-AM and PRE-PM, POST-PM respectively) for each subject using a telemetry pill (HQ Inc, USA). RESULTS: There was a different pattern of Tc response over the two HOT days compared with the NORM day due to the significant increase in Tc associated with each of the heat exposures (p<0.01, PRE to POST, Table 1). Mean Tc did not reach 38°C, but in 10 out of 44 individual exposures subjects had a T above 38°C post heat exposure. In contrast, baseline T for the three days was not significantly different and showed a consistent significant increase to PRE-AM values (p<0.01, BASE to PRE-AM, Table 1) associated with the wearing of protective clothing and morning activities. The mean (±sd) unit temperatures of the HOT and NORM days were 160.2 (±89.3) and 27.6 (±8.4) °C respectively. CONCLUSION: The physiological strain experienced due to heat exposure in firefighter instructors resulted in a significant increase in Tc above that experienced during similar physical exertion with no heat exposure. While mean Tc did not reach 38°C, defined as an acceptable limit for work, Tc did rise above 38°C after approximately 1 in 4 individual heat exposures.

This study assessed the reproducibility of performance and selected metabolic variables during a variable high-intensity endurance cycling test. 8 trained male cyclists (age: 35.9 ± 7.7 years, maximal oxygen uptake: 54.3 ± 3.9 mL·kg - 1·min - 1) completed 4 high-intensity cycling tests, performed in consecutive weeks. The protocol comprised: 20 min of progressive incremental exercise, where the power output was increased by 5% maximal workload (Wmax) every 5 min from 70% Wmax to 85% Wmax; ten 90 s bouts at 90% Wmax, separated by 180 s at 55% Wmax; 90% Wmax until volitional exhaustion. Blood samples were drawn and heart rate was monitored throughout the protocol. There was no significant order effect between trials for time to exhaustion (mean: 4 113.0 ± 60.8 s) or total distance covered (mean: 4 6126.2 ± 1 968.7 m). Total time to exhaustion and total distance covered showed very high reliability with a mean coefficient of variation (CV) of 1.6% (95% Confidence Intervals (CI) 0.0 ± 124.3 s) and CV of 2.2% (95% CI 0.0 ± 1904.9 m), respectively. Variability in plasma glucose concentrations across the time points was very small (CV 0.46-4.3%, mean 95% CI 0.0 ± 0.33 to 0.0 ± 0.94 mmol·L - 1). Plasma lactate concentrations showed no test order effect. The reliability of performance and metabolic variables makes this protocol a valid test to evaluate nutritional interventions in endurance cycling.

Nitrate-rich beetroot juice (BRJ) increases plasma nitrite concentrations, lowers the oxygen cost (V̇O2) of steady-state exercise and improves exercise performance in sedentary and moderately-trained, but rarely in well-trained individuals exercising at sea-level. BRJ supplementation may be more effective in a hypoxic environment, where the reduction of nitrite into nitric oxide (NO) is potentiated, such that well-trained and less well-trained individuals may derive a similar ergogenic effect. We conducted a randomised, counterbalanced, double-blind placebo controlled trial to determine the effects of BRJ on treadmill running performance in moderate normobaric hypoxia (equivalent to 2500 m altitude) in participants with a range of aerobic fitness levels. Twelve healthy males (V̇O2max ranging from 47.1 to 76.8 ml kg(-1)·min(-1)) ingested 138 ml concentrated BRJ (∼15.2 mmol nitrate) or a nitrate-deplete placebo (PLA) (∼0.2 mmol nitrate). Three hours later, participants completed steady-state moderate intensity running, and a 1500 m time-trial (TT) in a normobaric hypoxic chamber (FIO2 ∼15%). Plasma nitrite concentrations were significantly greater following BRJ versus PLA 1 h post supplementation, and remained higher in BRJ throughout the testing session (p < 0.01). Average V̇O2 was significantly lower (BRJ: 18.4 ± 2.0, PLA: 20.4 ± 12.6 ml kg(-1)·min(-1); p = 0.002), whilst arterial oxygen saturation (SpO2) was significantly greater (BRJ: 88.4 ± 2.7, PLA: 86.5 ± 3.3%; p < 0.001) following BRJ. BRJ improved TT performance in all 12 participants by an average of 3.2% (BRJ: 331.1 ± 45.3 vs. PL: 341.9 ± 46.1 s; p < 0.001). There was no apparent relationship between aerobic fitness and the improvement in performance following BRJ (r(2) = 0.05, p > 0.05). These findings suggests that a high nitrate dose in the form of a BRJ supplement may improve running performance in individuals with a range of aerobic fitness levels conducting moderate and high-intensity exercise in a normobaric hypoxic environment.

INTRODUCTION: Whilst the link between physical factors and risk of high altitude (HA)-related illness and acute mountain sickness (AMS) have been extensively explored, the influence of psychological factors has been less well examined. In this study we aimed to investigate the relationship between 'anxiety and AMS risk during a progressive ascent to very HA. METHODS: Eighty health adults were assessed at baseline (848m) and over 9 consecutive altitudes during a progressive trek to 5140m. HA-related symptoms (Lake Louise [LLS] and AMS-C Scores) and state anxiety (State-Trait-Anxiety-Score [STAI Y-1]) were examined at each altitude with trait anxiety (STAI Y-2) at baseline. RESULTS: The average age was 32.1 ± 8.3 years (67.5% men). STAI Y-1 scores fell from 848m to 3619m, before increasing to above baseline scores (848m) at ≥4072m (p = 0.01). STAI Y-1 scores correlated with LLS (r = 0.31; 0.24-0.3; P<0.0001) and AMS-C Scores (r = 0.29; 0.22-0.35; P<0.0001). There was significant main effect for sex (higher STAI Y-1 scores in women) and altitude with no sex-x-altitude interaction on STAI Y-1 Scores. Independent predictors of significant state anxiety included female sex, lower age, higher heart rate and increasing LLS and AMS-C scores (p<0.0001). A total of 38/80 subjects (47.5%) developed AMS which was mild in 20 (25%) and severe in 18 (22.5%). Baseline STAI Y-2 scores were an independent predictor of future severe AMS (B = 1.13; 1.009-1.28; p = 0.04; r2 = 0.23) and STAI Y-1 scores at HA independently predicted AMS and its severity. CONCLUSION: Trait anxiety at low altitude was an independent predictor of future severe AMS development at HA. State anxiety at HA was independently associated with AMS and its severity.

INTRODUCTION: Dietary nitrate supplementation increases nitric oxide (NO) bioavailability, and has been shown to improve exercise performance in hypoxia (i.e. a low-oxygen environment) in some (e.g. Muggeridge et al., 2014, Med Sci Sports Exerc, 46:143-150) but not all (e.g. Arnold et al., 2015, Appl. Physiol. Nutr. Metab., 40: 590-595) studies. The precise conditions under which nitrate consumption is ergogenic remains to be established. The aim of this study was to assess the effects of nitrate-rich beetroot juice on the physiological response to steady-state exercise, and 1500 m time-trial (TT) performance in trained runners exercising in moderate normobaric hypoxia (equivalent to 2500 m altitude). METHODS: Six trained runners (age: 23.3 ± 1.9 years; sea-level V̇O2max: 64.6 ± 10.2 ml·kg-1·min-1; altitude V̇O2max: 53.1 ± 7.9 ml·kg-1·min-1) visited the laboratory on five separate occasions, including incremental running tests in normoxia (1) and hypoxia (2) to determine V̇O2max; a familiarization trial (3); and two performance trials (4 + 5). On the morning of the performance trials, participants consumed 138 ml concentrated nitrate-rich (reported to contain ~12.5 mmol nitrate) or a nitrate-deplete (~0 mmol nitrate) beetroot juice. Three hours later, participants completed two, 15 minute steady-state bouts of running at 45 and 65 % of altitude V̇O2max, respectively, and a 1500 m TT in a normobaric hypoxic chamber (PIO2 107.5 mmHg, FIO2 ~15 %). Exhaled NO was measured pre-supplementation, pre-hypoxic exposure, pre-exercise and post-TT. VO2 was monitored during steady-state exercise, and arterial oxygen saturation (SaO2) was monitored pre-hypoxic exposure, pre-exercise, during steady-state exercise, and post-TT. RESULTS: Nitrate supplementation significantly elevated exhaled NO versus placebo (Placebo: 20.5 ± 20.5 vs. Nitrate: 45.5 ± 30.6 p.p.b., p = 0.044). Average VO2 was significantly lower during steady-state exercise (Placebo: 27.6 ± 5.4 vs. Nitrate: 25.0 ± 4.5 ml·kg-1·min-1, p = 0.029), whilst average SaO2 was significantly greater (Placebo: 85.9 ± 2.6 vs. Nitrate: 88.2 ± 2.8 %, p = 0.02) with nitrate ingestion. TT performance was significantly faster (Placebo: 346.8 ± 43.3 s vs. Nitrate: 335.1 ± 42.3 s, p = 0.01, Cohen’s d = 0.272) following nitrate supplementation. CONCLUSION: Dietary nitrate supplementation increases exhaled NO, reduces steady-state VO2, and elevates SaO2 during steady-state exercise, and results in a small (3.4 %) but significant improvement in 1500 m TT performance relative to a placebo. Therefore, nitrate-rich beetroot juice may represent a viable ergogenic aid for enhancing 1500 m running performance in trained athletes exercising in moderate normobaric hypoxia.

Purpose: Exposure to high altitude has been shown to enhance both glucose and lipid utilization depending on experimental protocol. In addition, high and low blood glucose levels have been reported at high altitude. We hypothesized that gradual ascent to high altitude results in changes in glucose levels in healthy young adults. Methods: 25 adult volunteers, split into two teams, took part in the British Services Dhaulagiri Medical Research Expedition completing 14 days of trekking around the Dhaulagiri circuit in Nepal reaching a peak altitude of 5300m on Day 11 of the trek. Participants wore blinded continuous glucose monitors (CGM) throughout. Blood samples for c-peptide, pro-insulin and triacylglycerides were taken at sea level (UK) and in acclimatisation camps at 3600m, 4650m and 5120m. Energy intake was determined from food diaries. Results: There was no difference in time spent in hypoglycemia stratified by altitude. Nocturnal CGM readings (22.00-06.00 hrs) were chosen to reduce the short-term impact of physical activity and food intake and showed a significant (p<0.0001) increase at 3600m (5.53±0.22mmol/L), 4650m (4.77±0.30mmol/L) and 5120m (4.78±0.24mmol/L) compared to baseline altitude 1100m (vs 4.61±0.25mmol/L). Energy intake did not differ by altitude. Insulin resistance and B-cell function, calculated by homeostatic model assessment, was reduced at 3600m compared to sea level. Conclusions: We observed a significant increase in nocturnal CGM glucose at 3600m and above despite gradual ascent from 1100m. Taken with the changes in insulin resistance and B-cell function, it is possible that the stress response to high altitude dominates exercise enhanced insulin sensitivity, resulting in relative hyperglycemia.

There is evidence to suggest that high altitude (HA) exposure leads to a fall in heart rate variability (HRV) that is linked to the development of acute mountain sickness (AMS). The effects of sex on changes in HRV at HA and its relationship to AMS are unknown. HRV (5-minute single lead ECG) was measured in 63 healthy adults (41 men and 22 women) aged 18-56 years at sea level (SL) and during a HA trek at 3619m, 4600m and 5140m respectively. The main effects of altitude (SL, 3619, 4600 and 5140m) and sex (men vs women) and their potential interaction were assessed using a Factorial Repeated Measures ANOVA. Logistic regression analyses were performed to assess the ability of HRV to predict AMS. Men and women were of similar age (31.2 ±9.3 vs 31.7±7.5 years), ethnicity, body and mass index. There was main effect for altitude on heart rate, SDNN (standard deviation [SD] of normal-to-normal [NN] intervals), RMSSD (Root mean square of successive differences), NN50 (number of pairs of successive NNs differing by >50 ms), pNN50 (NN50 / total number of NNs), very low frequency (VLF), low frequency (LF), high frequency (HF) and total power (TP). The most consistent effect on post hoc analysis was reduction in these HRV measures between 3619 and 5140m at HA. Heart rate was significantly lower and SDNN, RMSSD, LF, HF and TP were higher in men compared with women at HA. There was no interaction between sex and altitude for any of the HRV indices measured. HRV was not predictive of AMS development. Increasing HA leads to a reduction in HRV. Significant differences between men and women emerge at HA. HRV was not predictive of AMS.

ORAL PRESENTATION Purpose: To evaluate and compare the acute group and individual endogenous hormone responses to three resistance exercise workouts and two load carriage workouts. Understanding hormone responses specific to military settings may enhance training optimisation in the future. Methods: Eighteen resistance exercise-trained male civilians (age: 19 to 38 y, mean 24.9 y) completed five experimental workouts and a control condition in a randomised order; three resistance exercise workouts (cluster, hypertrophy, endurance), two load carriage (90-min constant pace [CO-LC] or 6 × 8-min intervals [IT-LC], both carrying a rucksack with 25% body mass) workouts, and a control condition (60-minutes of rest). Venous blood was drawn before, immediately post workout, and 30-min and 24-h post workout. Testosterone (T), free testosterone (fT), growth hormone (GH), dehydroepiandrosterone sulphate (DHEAS), androstenedione (ANST), and insulin-like growth factor 1 (IGF-1) concentrations were subsequently analysed via liquid chromatography-mass spectrometry. Group responses were evaluated using two-way ANOVA’s with Tukey’s post-hoc analysis. The standardised standard deviations of the pre-post change scores (SDIR) were calculated to identify the presence of individual responses (Hopkins, 2015). Results: Group responses were observed despite large individual variations. T concentrations increased in response to hypertrophy (p < 0.001) and CO-LC (p = 0.02) workouts; fT concentrations increased in response to CO-LC (p < 0.001) and decreased following the hypertrophy (p = 0.035) workout; ANST concentrations increased in response to CO-LC (p = 0.007); GH increased following hypertrophy (p = 0.004), endurance (p = 0.04), IT-LC (p < 0.001), and CO-LC (p < 0.001) workouts; IGF-1 increased in response to the endurance (p = 0.018) workout. The SDIR effect size thresholds of extremely large (T, GH, DHEAS) and very large (T, GH, DHEAS, ANST, IGF-1) were achieved, representing an individualised pattern of hormone production in response to the different resistance exercise and load carriage workouts. Conclusions: The presence of within-workout variations in the hormonal responses to all workout types suggests that the mean group responses may not reflect the response experienced by all participants, and that the hormonal anabolic response differs between individuals. The group responses and within-workout variation suggest that a wide panel of endogenous hormones should be measured to provide clarity on the anabolic response to different types of training stimuli at the individual level. Military Impact: The anabolic response to training type differs between individuals. This research provides support to further investigate whether training interventions based upon an individualised anabolic hormone response to acute exercise lead to improved physical outcomes. Funding for this research was provided by Dstl MOD. References: Hopkins W. J Appl Physiol, 118:1444–1446,2015; doi:10.1152/japplphysiol.00098.2015

Exposure to altitude results in multiple physiological consequences. These include, but are not limited to, a reduced maximal oxygen consumption, drop in arterial oxygen saturation, and increase in muscle metabolic perturbations at a fixed sub-maximal work rate. Exercise capacity during fixed work rate or incremental exercise and time-trial performance are also impaired at altitude relative to sea-level. Recently, dietary nitrate (NO3-) supplementation has attracted considerable interest as a nutritional aid during altitude exposure. In this review, we summarise and critically evaluate the physiological and performance effects of dietary NO3- supplementation during exposure to simulated and terrestrial altitude. Previous investigations at simulated altitude indicate that NO3- supplementation may reduce the oxygen cost of exercise, elevate arterial and tissue oxygen saturation, improve muscle metabolic function, and enhance exercise capacity/ performance. Conversely, current evidence suggests that NO3- supplementation does not augment the training response at simulated altitude. Few studies have evaluated the effects of NO3- at terrestrial altitude. Current evidence indicates potential improvements in endothelial function at terrestrial altitude following NO3- supplementation. No effects of NO3- supplementation have been observed on oxygen consumption or arterial oxygen saturation at terrestrial altitude, although further research is warranted. Limitations of the present body of literature are discussed, and directions for future research are provided.

Limited data exists on the hydration status of female athletes, with no data available on female rugby players. The objective of this study was to investigate the habitual hydration status on arrival, sweat loss, fluid intake, sweat Na loss and blood [Na] during field training and match-play in ten international female rugby league players. Urine osmolality on arrival to match-play (382 ± 302 mOsmol·kg) and training (667 ± 260 mOsmol·kg) was indicative of euhydration. Players experienced a body mass loss of 0.50 ± 0.45 and 0.56 ± 0.53% during match-play and training respectively. During match-play players consumed 1.21 ± 0.43 kg of fluid and had a sweat loss of 1.54 ± 0.48 kg. During training players consumed 1.07 ± 0.90 kg of fluid, in comparison to 1.25 ± 0.83 kg of sweat loss. Blood [Na] was well regulated ([INCREMENT]-0.7 ± 3.4 and [INCREMENT]-0.4 ± 2.6 mmol·L) despite sweat [Na] of 47.8 ± 5.7 and 47.2 ± 6.3 mmol·L during match-play and training. The findings of this study show mean blood [Na] appears to be well regulated despite losses of Na in sweat and electrolyte free fluid consumption. For the duration of the study players did not experience a body mass loss (dehydration >2%) indicative of a reduction in exercise performance, thus habitual hydration strategies appear adequate. Practitioners should evaluation the habitual hydration status of athletes to determine if interventions above habitual strategies are warranted.

Introduction Heat adaptation is protective against heat illness; however, its role in heat syncope, due to reflex mechanisms, has not been conclusively established. The aim of this study was to evaluate if heat acclimation (HA) was protective against heat syncope and to ascertain underlying physiological mechanisms. Methods Twenty (15 males, 5 females) endurance-trained athletes were randomized to either 8 d of mixed active and passive HA (HEAT) or climatically temperate exercise (CONTROL). Before, and after, the interventions participants underwent a head up tilt (HUT) with graded lower body negative pressure (LBNP), in a thermal chamber (32.0 ± 0.3°C), continued until presyncope with measurement of cardiovascular parameters. Heat stress tests (HST) were performed to determine physiological and perceptual measures of HA. Results There was a significant increase in orthostatic tolerance (OT), as measured by HUT/LBNP, in the HEAT group (preintervention; 28 ± 9 min, postintervention; 40 ± 7 min) compared with CONTROL (preintervention; 30 ± 8 mins, postintervention; 33 ± 5 min) (P = 0.01). Heat acclimation resulted in a significantly reduced peak and mean rectal and skin temperature (P < 0.01), peak heat rate (P < 0.003), thermal comfort (P < 0.04), and rating of perceived exertion (P < 0.02) during HST. There was a significantly increased plasma volume (PV) in the HEAT group in comparison to CONTROL (P = 0.03). Conclusions Heat acclimation causes improvements in OT and is likely to be beneficial in patients with heat exacerbated reflex syncope. Heat acclimation–mediated PV expansion is a potential physiological mechanism underlying improved OT.

Two of the leading competitions in rugby league are the European Super League (SL) and Australasian National Rugby League (NRL); however, they adopt different officiating systems. The SL operates with one referee, whereas the NRL operates with two referees (NRL head and NRL pocket referees). There is currently no research comparing the movement demands of the referees using these two systems. This study evaluated the movement demands of SL referees and NRL head and pocket referees during rugby league match play using global positioning system (GPS) tracking. With institutional ethical approval, time–motion analysis was undertaken on 8 full-time SL referees and 19 NRL referees using portable 10 Hz GPS devices (MinimaxX; Catapult Sports, Australia) during the SL and NRL 2013 seasons. A total of 230 matches (SL, n = 144; NRL head, n = 41; NRL pocket, n = 45) were analysed using Sprint software (Catapult Innovations, Australia). A one-way ANOVA was conducted with a Bonferroni post hoc to assess the differences between referees in addition to Cohen’s d effect sizes. The SL referees (6900 ± 830 m) and NRL head referees (7253 ± 1164 m) covered similar distances during match play, whilst the NRL pocket referees covered significantly greater distance (7539 ± 930 m, P < 0.001, d = 0.73) than the SL referees. When movement was categorised into velocity classifications (Rampini et al., 2007, International Journal of Sports Medicine, 28, 228–235) SL referees performed a significantly greater number of high-intensity efforts (9.7 ± 7.4) between 5.51 and 7.00 m · s-1 compared to both the NRL head (6.5 ± 4.2; P = 0.015, d = 0.51) and NRL pocket referees (6.4 ± 4.2; P = 0.009, d = 0.56). SL referees produced a similar number of low-intensity efforts (2.01–4.00 m · s-1) to the NRL head (215.0 ± 34.0 vs. 223.2 ± 45.9) and pocket referees (228.4 ± 37.9). The SL referees covered significantly less distance (3310 ± 510 m) accelerating between 0.00 and 1.00 m · s-2 than the NRL head (3609 ± 692 m; P = 0.010, d = 0.49) and the NRL pocket referees (3770 ± 631 m; P < 0.001, d = 0.80). There was no difference between SL (248 ± 186 m), NRL head (253 ± 176 m) and NRL pocket (268 ± 180 m) referees for distance covered when accelerating at >1.00 m · s-2. A comparison of the one-referee (SL) system with the two-referee (NRL head) system shows no effect on the total distance covered, low-intensity efforts or distance covered when accelerating above 1.00 m · s-2, during match play. However, the SL referees are required to perform more high-intensity efforts and cover less distance accelerating between 0.00 and 1.00 m · s-2 than NRL referees. This preliminary data suggest that the different refereeing systems may influence the movement demands of the referees.

It has previously been thought that reductions in inspired partial pressure of oxygen (PiO2) as a result of either reduced barometric pressure (PB) or inspired fraction of oxygen (FiO2) (normobaric hypoxia (NH)) would produce the same physiological responses. However, recent studies have reported differences between terrestrial altitude (TA) and NH. This may lead to differences in substrate utilisation during exercise; however, this is yet to be evaluated. The purpose was to compare whole-body substrate oxidation during s82 Day 2. Posters – Physiology and Nutrition Downloaded by exercise following co-ingestion of glucose and fructose on acute exposure to TA and NH. With institutional and Ministry of Defence ethical approval, eight male military personnel (age; 26.75 ± 4.86 years) completed a maximal oxygen uptake test and two experimental trials. These consisted of 2-hour cycling (~55%Wmax) at TA (3375 m; PiO2 ~ 96 mmHg) in the Italian Alps (Torino Hut) and in NH at an equivalent altitude (FiO2 ~ 13.8%, PiO2 ~ 96 mmHg). Carbohydrate (CHO) formulations (1.2 g · min-1 glucose and 0.6 g · min-1 fructose) were ingested immediately prior to and every 15 min throughout exercise. Whole-body substrate oxidation was measured using indirect calorimetry. Blood samples were drawn regularly for assessment of glucose, lactate, insulin and free fatty acids (FFA). Total energy expenditure was similar (P = 0.83; d = 0.03) in TA and NH (1285 ± 142 kcal and 1277 ± 98 kcal). Mean CHO oxidation during exercise was higher in NH (1.99 ± 0.25 g · min-1) compared to TA (1.20 ± 0.05 g · min-1), though not significant (P = 0.06; d = 0.91). The relative contribution ofCHO to the total energy yield was higher inNH compared to TA (69.82 ± 25.73% and 41.89 ± 22.57%), though not significant (P = 0.06; d = 0.50). Mean fat oxidation was higher at TA (0.72 ± 0.03 g · min-1) compared to NH (0.36 ± 0.07 g · min-1), though not significant (P = 0.06; d = 0.96). FFA concentrations were higher at TA compared to NH (P=0.003; d = 0.69), withTAproducing lower insulin concentrations than NH (P = 0.003; d = 0.46).There were no significant differences between the conditions for glucose (P = 0.06; d = 0.15) and lactate (P = 0.06; d = 0.19) concentrations. This study showed no significant difference in total energy expenditure at NH and TA. There was however evidence that the proportional part of CHO oxidation was increased during NH whilst the proportional part of fat oxidation was increased at TA. These differences just failed to reach statistical significance at the 5% level. Further investigation regarding substrate utilisation in reduced PB compared to FiO2 is warranted.

The hydration status of rugby league players during competitive home match play was assessed throughout the 2008 Super League season. Fourteen players from 2 Super League clubs were monitored (72 observations). On arrival, 2 h prior to kick off, following normal prematch routines, players' body mass were measured following a urine void. Prematch fluid intake, urine output, and osmolality were assessed until kick off, with additional measurements at half time. Fluid intake was also monitored during match play for club B only, and final measurements of variables were made at the end of the match. Mean body mass loss per match was 1.28 ± 0.7 kg (club A, 1.15 kg; club B, 1.40 kg), which would equate to an average level of dehydration of 1.31% (mass loss, assumed to be water loss, expressed as a percentage of body mass), with considerable intra-individual coefficient of variation (CV, 47%). Mean fluid intake for club B was 0.64 ± 0.5 L during match play, while fluid loss was 2.0 ± 0.7 L, with considerable intra-individual CV (51% and 34%, respectively). Mean urine osmolality was 396 ± 252 mosm·kg-1 on arrival, 237 ± 177 mosm·kg-1 prematch, 315 ± 133 mosm·kg-1 at half time, and 489 ± 150 mosm·kg-1 postmatch. Body mass losses were primarily a consequence of body fluid losses not being completely balanced by fluid intake. Furthermore, these data show that there is large inter- and intra-individual variability of hydration across matches, highlighting the need for future assessment of individual relevance.

Purpose: To evaluate the movement and physiological demands of the Australasian National Rugby League (NRL) referees, officiating with a ‘two referee’ (i.e., ‘lead’ and ‘pocket’) system and to compare the demands of the lead referee and pocket referees. Methods: 10 Hz global positioning system devices were used to obtain 86 data sets (‘lead’, n=41; ‘pocket’, n=45) on 19 NRL referees. Total distance, relative distance covered and heart rate per half and across match-play was examined within and between referees using t-tests. Distance, time and number of movement 'efforts' were examined in six velocity classifications (i.e., standing <0.5; walking 0.51–2.0; jogging 2.01-4.0; running 4.01-5.5; high speed running 5.51-7.0; sprinting > 7.0 m.s-1) using ANOVA. Cohen's d effect sizes were reported. Results: There were no significant differences between the ‘lead’ and ‘pocket’ referee for any movement or physiological variable. There was an overall significant (large; very large) effect for distance (% distance) and time (% time) (P < 0.001) between each velocity classification for both the ‘lead’ and ‘pocket’ referee. Both roles covered the largest distance and number of efforts at velocities between 0.51–2.0 m.s-1 and 2.01-72 4.0 m.s-1, which were interspersed with efforts >5.51 m.s-1. Conclusions: Findings highlight the intermittent nature of rugby league refereeing, but show that there were no differences in the movement and physiological demands of the two refereeing roles. Findings are valuable for those responsible for the preparation, training and conditioning of NRL referees, and to ensure training prepares for and simulates match demands.

This study aimed to establish whether a series of 3 apneas before a 400-m freestyle time-trial affected swimming performance when compared with and combined with a warm-up. Nine (6 males and 3 females) regional to national standard swimmers completed four 400-m freestyle time-trials in 4 randomized conditions: without warm-up or apneas (CON), warm-up only (WU), apneas only (AP), and warm-up and apneas (WUAP). Time-trial performance was significantly improved after WUAP (275.79 ± 12.88 seconds) compared with CON (278.66 ± 13.31 seconds, p = 0.035) and AP (278.64 ± 4.10 seconds, p = 0.015). However, there were no significant differences between the WU (276.01 ± 13.52 seconds, p > 0.05) and other interventions. Spleen volume compared with baseline was significantly reduced after the apneas by a maximum of ∼45% in the WUAP and by ∼20% in WU. This study showed that the combination of a warm-up with apneas could significantly improve 400-m freestyle swim performance compared with a control and apnea intervention. Further investigation into whether long-term apnea training can enhance this response is justified.

Rugby league referees have the responsibility of enforcing the laws of the game and can influence the outcome based on their decisions. Performance demands inherent in refereeing involve fitness and positioning, law knowledge and application, contextual judgement and game management (Weston et al., 2012, International Journal of Sports Medicine, 42, 615–617). No study to date has investigated the relationship between the physiological and movement demands of refereeing and penalty accuracy. To quantify penalty accuracy scores of rugby league referees and determine the relationship with total distance covered (TD), high intensity distance (HIT) and mean heart rate per half and 10-min period of a match. With institutional ethical approval, all 8 professional Super League referees participated in this study. During the 2012 season, 148 Super League matches were analysed using 10Hz GPS units (MinimaxV4; Catapult Sports, Australia) and 1-Hz heart rate monitors (Polar Electro, Kempele, Finland). Decision-making demands were quantified using Opta Stats (Leeds, UK), which were retrospectively reviewed by an expert referee review panel to determine the accuracy of decisions when awarding or not awarding a penalty. A dependant t-test was used to assess the differences between halves. Repeated measures ANOVA was conducted with a Bonferroni post hoc to assess the differences between 10-min match periods, in addition to Cohen’s d effect sizes. Pearson’s product correlation was used to determine relationships. Super League referees made the correct penalty decision on 74 ± 5% of occasions. Significantly more distance was covered (3586 ± 394 vs. 3514 ± 424 m, P = 0.009, d = 0.18), and a significantly greater heart rate (154 ± 9 vs. 149 ± 9 beats.min-1, P = 0.001, d = 0.56) was achieved in the first compared to the second half. There was no significant difference (P = 0.812) in penalty accuracy (75 ± 4 vs. 73 ± 6 %) or HIT (P = 0.081) between halves. When observed per half and 10 minute periods, there was no significant relationship between penalty accuracy scores and TD (r = –0.023, P = 0.645), HIT (r = 0.093, P = 0.18) or heart rate (r = 0.129, P = 0.135). Findings suggest that the physiological and movement demands of refereeing in rugby league are not significantly related to penalty accuracy scores per 40-min or 10-min period. While it has been observed that there was no significant relationship between TD, HIT or heart rate and accuracy, further research is required to investigate confounding variables (i.e. refereeing experience and fitness levels) that may further influence penalty accuracy. Given the small sample population of professional referees (n = 8), a case study approach to future research is recommended.

Background: A better understanding of hypoxia-induced changes in substrate utilisation can facilitate the development of nutritional strategies for mountaineers, military personnel and athletes during exposure to altitude. However, reported metabolic responses are currently divergent. As such, this systematic review and meta-analysis aims to determine the changes in substrate utilisation during exercise in hypoxia compared with normoxia and identify study characteristics responsible for the heterogeneity in findings. Methods: A total of six databases (PubMed, the Cochrane Library, MEDLINE, SPORTDiscus, PsychINFO, and CINAHL via EBSCOhost) were searched for published original studies, conference proceedings, abstracts, dissertations and theses. Studies were included if they evaluated respiratory exchange ratio (RER) and/or carbohydrate or fat oxidation during steady state exercise matched for relative intensities in normoxia and hypoxia (normobaric or hypobaric). A random-effects meta-analysis was performed on outcome variables. Meta-regression analysis was performed to investigate potential sources of heterogeneity. Results: In total, 18 studies were included in the meta-analysis. There was no significant change in RER during exercise matched for relative exercise intensities in hypoxia, compared with normoxia (mean difference: 0.01, 95% CI: -0.02 to 0.05; n = 31, p = 0.45). Meta-regression analysis suggests that consumption of a pre-exercise meal (p < 0.01) and a higher exercise intensity (p = 0.04) when exposed to hypoxia may increase carbohydrate oxidation compared with normoxia. Conclusions: Exposure to hypoxia did not induce a consistent change in the relative contribution of carbohydrate or fat to the total energy yield during exercise matched for relative intensities, compared with normoxia. The direction of these responses appears to be mediated by the consumption of a pre-exercise meal and exercise intensity. Key words: Altitude, exercise, substrate, carbohydrate, fat, oxidation, systematic review

The purpose of this study was to assess the reliability of a pre-loaded 1500 m treadmill time-trial, conducted in moderate normobaric hypoxia. Eight trained runners/ triathletes (24 ± 3 years, 73.2 ± 8.1 kg, 182.5 ± 6.5 cm, altitude specific V̇O2max: 52.9 ± 5.5 ml·kg-1·min-1) completed three trials (the first as a familiarisation), involving two, 15 minute running bouts at 45 % and 65 % V̇O2max, respectively, and a 1500 m time-trial in moderate normobaric hypoxia equivalent to a simulated altitude of 2500 m (FiO2 ~ 15 %). Heart rate, arterial oxygen saturation, skeletal muscle and cerebral tissue oxygenation (StO2), expired gas (V̇O2 and V̇CO2), and ratings of perceived exertion were monitored. Running performance (Trial 1: 352.7 ± 40; Trial 2: 353.9 ± 38.2 s) demonstrated a low CV (0.9 %) and high ICC (1). All physiological variables demonstrated a global CV ≤ 4.2 %, and ICC ≥ 0.87, with the exception of muscle (CV 10.4 %; ICC 0.70) and cerebral (CV 4.1 %; ICC 0.82) StO2. These data demonstrate good reliability of the majority of physiological variables, and indicate that a pre-loaded 1500 m time-trial conducted in moderate normobaric hypoxia is a highly reliable test of performance.

Purpose This study evaluated the effects of dietary nitrate (NO3-) supplementation on physiological functioning and exercise performance in trained runners/ triathletes conducting short and longer distance treadmill running time-trials (TT). Method Eight trained male runners or triathletes completed four exercise performance tests comprising a 10 minute warm up followed by either a 1500 m or 10,000 m treadmill TT. Exercise performance tests were preceded 3 hours before the exercise by supplementation with either 140 ml concentrated nitrate-rich (~ 12.5 mmol nitrate) (BRJ) or nitrate-deplete (~ 0.01 mmol nitrate) (PLA) beetroot juice. Results BRJ supplementation significantly elevated plasma [NO2-] (P < 0.05). Resting blood pressure and exercise V̇O2 were not significantly different between BRJ and PLA (P > 0.05). However, post-exercise blood [lactate] was significantly greater in BRJ following the 1500 m TT (6.6 ± 1.2 vs. 6.1 ± 1.5 mM; P < 0.05), but not significantly different between conditions in the 10,000 m TT (P > 0.05). Performance in the 1500 m TT was significantly faster in BRJ versus PLA (319.6 ± 36.2 vs. 325.7 ± 38.8 s; P < 0.05). Conversely, there was no significant difference in 10,000 m TT performance between conditions (2643.1 ± 324. 1 vs. 2649.9 ± 319.8 s, P > 0.05). Conclusion Acute BRJ supplementation significantly enhanced 1500 m but not 10,000 m TT performance. These findings suggest that BRJ might be ergogenic during shorter-distance TTs which allow for a high work rate, but not during longer-distance TTs, completed at a lower work rate.

Central arterial systolic blood pressure (SBP) and arterial stiffness are known to be better predictors of adverse cardiovascular outcomes than brachial SBP. The effect of progressive high altitude (HA) on these parameters has not been examined. Ninety healthy adults were included. Central BP and the augmentation index (AI) were measured at the level of the brachial artery (Uscom BP + device) at <200 m and at 3619, 4600 and 5140 m. The average age of the subjects (70% men) were 32.2±8.7 years. Compared with central arterial pressures, brachial SBP (+8.1±6.4 mm Hg; P<0.0001) and pulse pressure (+10.9±6.6 mm Hg; P<0.0001) were significantly higher and brachial diastolic BP was lower (-2.8±1.6 mm Hg; P<0.0001). Compared with <200 m, HA led to a significant increase in brachial and central SBP. Central SBP correlated with AI (r=0.50; 95% confidence interval (CI): 0.41-0.58; P<0.0001) and age (r=0.32; 95% CI: 21-0.41; P<0.001). AI positively correlated with age (r=0.39; P<0.001) and inversely with subject height (r=-0.22; P<0.0001), weight (r=-0.19; P=0.006) and heart rate (r=-0.49; P<0.0001). There was no relationship between acute mountain sickness scores (Lake Louis Scoring System (LLS)) and AI or central BP. The independent predictors of central SBP were male sex (coefficient, t=4.7; P<0.0001), age (t=3.6; P=0.004) and AI (t=7.5; P<0.0001; overall r 2 =0.40; P<0.0001). Subject height (t=2.4; P=0.02), age (7.4; P<0.0001) and heart rate (t=11.4; P<0.0001) were the only independent predictors of AI (overall r 2 =0.43; P<0.0001). Central BP and AI significantly increase at HA. This rise was influenced by subject-related factors and heart rate but not independently by altitude, LLS or SpO 2.

Postural control and joint position sense are essential for safely undertaking leisure and professional activities, particularly at high altitude. We tested whether exposure to a 12-day trek with a gradual ascent to high altitude impairs postural control and joint position sense. This was a repeated measures observational study of 12 military service personnel (28±4 years). Postural control (sway velocity measured by a portable force platform) during standing balance, a Sharpened Romberg Test and knee joint position sense were measured, in England (113m elevation) and at 3 research camps (3619m, 4600m and 5140m) on a 12-day high altitude trek in the Dhaulagiri region of Nepal. Pulse oximetry, and Lake Louise scores were also recorded on the morning and evening of each trek day. Data were compared between altitudes and relationships between pulse oximetry, Lake Louise score, and sway velocity were explored. Total sway velocity during standing balance with eyes open (p = 0.003, d = 1.9) and during Sharpened Romberg test with eyes open (p = 0.007, d = 1.6) was significantly greater at altitudes of 3619m and 5140m when compared with sea level. Anterior-posterior sway velocity during standing balance with eyes open was also significantly greater at altitudes of 3619m and 5140m when compared with sea level (p = 0.001, d = 1.9). Knee joint position sense was not altered at higher altitudes. There were no significant correlations between Lake Louise scores, pulse oximetry and postural sway. Despite a gradual ascent profile, exposure to 3619 m was associated with impairments in postural control without impairment in knee joint position sense. Importantly, these impairments did not worsen at higher altitudes of 4600 m or 5140 m. The present findings should be considered during future trekking expeditions when developing training strategies targeted to manage impairments in postural control that occur with increasing altitude.

The purpose of this study was to investigate changes in postural control and knee joint position sense (KJPS)during a trek to high altitude. Postural control during standing balance and KJPS were measured in 12 participants at sea-level, 3619m, 4600m and 5140m. Total (p = 0.003, d=1.9) and anterior-posterior sway velocity (p= 0.001, d=1.9) during standing balance with eyes open velocity was significantly greater at altitudes of 3619m and 5140m when compared with sea level. Despite a gradual ascent profile, exposure to 3619 m was associated with impairments in postural control. Importantly, these impairments did not worsen at higher altitudes. The present findings should be considered during future trekking expeditions when considering specific strategies to manage impairments in postural control that occur with increasing altitude.

The purpose of this study was to investigate changes in postural control and knee joint position sense (KJPS) during a trek to high altitude. Postural control during standing balance and KJPS were measured in 12 participants at sea-level, 3619m, 4600m and 5140m. Total (p = 0.003, d=1.9) and anterior-posterior sway velocity (p= 0.001, d=1.9) during standing balance with eyes open velocity was significantly greater at altitudes of 3619m and 5140m when compared with sea level. Despite a gradual ascent profile, exposure to 3619 m was associated with impairments in postural control. Importantly, these impairments did not worsen at higher altitudes. The present findings should be considered during future trekking expeditions when considering specific strategies to manage impairments in postural control that occur with increasing altitude.

Purpose To investigate whether there is a differential response at rest and following exercise to conditions of genuine high altitude (GHA), normobaric hypoxia (NH), hypobaric hypoxia (HH) and normobaric normoxia (NN). Method Markers of sympathoadrenal and adrenocortical function (plasma normetanephrine [PNORMET], metanephrine [PMET], cortisol), myocardial injury (highly sensitive cardiac troponin T [hscTnT]) and function (N-terminal brain natriuretic peptide [NT-proBNP]) were evaluated at rest and with exercise under NN, at 3375 m in the Alps (GHA) and at equivalent simulated altitude under NH and HH. Participants cycled for 2 hours {15 minute warm-up, 105 minutes at 55% Wmax (maximal workload)} with venous blood samples taken prior (T0), immediately following (T120) and 2 hours post-exercise (T240). Results Exercise in the three hypoxic environments produced a similar pattern of response with the only difference between environments being in relation to PNORMET. Exercise in NN only induced a rise in PNORMET and PMET. Conclusion Biochemical markers that reflect sympathoadrenal, adrenocortical and myocardial responses to physiological stress demonstrate significant differences in the response to exercise under conditions of normoxia versus hypoxia while NH and HH appear to induce broadly similar responses to GHA and may therefore be reasonable surrogates.

The ergogenic benefits of carbohydrate (CHO) ingestion in cycling and running have been widely reported. Studies directly comparing the effect of CHO ingestion on CHO oxidation rates in cycling and running suggest no difference in exogenous CHO oxidation between these exercise modes. Potential differences in endogenous fuel use between cycling and running when ingesting CHO may lead to a greater benefit in cycling rather than running time trial (TT) performance. Direct comparisons of the effect of CHO ingestion during endurance exercise on subsequent cycling or running TT performance are limited. This study tested the hypothesis that ingesting CHO during 120 min of constant intensity exercise would benefit subsequent TT performance more in cycling than running. Methods: In a randomised, placebo controlled, double blind crossover trial, 10 male triathletes (VO2 max cycle 51.65±5.53, run 59.07±6.14 mL kg min ) completed 4 separate exercise trials. Each trial consisted of cycling or running at 70% of mode specific VO2max for 120min whilst ingesting either a CHO drink (2:1 glucose: fructose, 90g h ) or an equal volume of taste matched 0% CHO placebo (PLA) (750mL h ). After 10min recovery, participants completed a TT in the same mode of exercise, running 6km or cycling 16km. The CHO drink was enriched with uniformly labelled C glucose and C fructose isotopes to quantify exogenous and endogenous CHO oxidation. Due to limitations of the tracer methods used in the first hour, only data for the final 60min of exercise are presented. Total CHO and fat oxidation rates were calculated from expired air using stoichiometric equations. Data were analysed using ANOVA, values are means±SD. Results: From 60 120 min of exercise mean fat oxidation rates did not differ between exercise modes (PLA cycle 0.52±0.17, run 0.56±0.22g min p=0.86; CHO cycle 0.37±0.12 run 0.40±0.17g min , p=0.82). CHO ingestion reduced fat oxidation within cycling (p<0.01) and running trials (p=0.02) compared to PLA. Mean total CHO oxidation rates did not differ between trials (PLA cycle 2.52±0.74, run 2.21±0.46g min , p=0.23, CHO cycle 2.95±0.40, run 2.77±0.55g min , p=0.47). Mean exogenous CHO oxidation did not differ with CHO ingestion (cycle 0.87±0.22 run 0.75±0.31g min , p=0.31). CHO ingestion reduced endogenous CHO oxidation in cycling (PLA 2.52±0.74, CHO 2.10±0.41g min , p=0.03) but not running (PLA 2.21±0.46, CHO 2.00±0.61g min , p=0.44). TT performance improved 10% in cycling and 3% in running after CHO ingestion (p<0.01). TT performance improvement was greater in cycling than running (p=0.04, ES=1.45). Conclusions: This study demonstrates a greater improvement in cycling versus running TT performance after CHO ingestion. This may relate to the greater sparing of endogenous CHO in cycling versus running during the previous exercise period when CHO is ingested.

Super League (SL) and Championship (RLC) rugby league players will compete against each other in 2015 and beyond. To identify possible discrepancies, this study compared the anthropometric profile and body composition of current SL (full-time professional) and RLC (part-time semi-professional) players using dual-energy X-ray absorptiometry (DXA). A cross-sectional design involved DXA scans on 67 SL (n=29 backs, n=38 forwards) and 46 RLC (n=20 backs, n=26 forwards) players during preseason. A one-way ANOVA was used to compare age, stature, body mass, soft tissue fat percentage, bone mineral content (BMC), total and regional (i.e., arms, legs and trunk) fat and lean mass between SL forwards, SL backs, RLC forwards and RLC backs. No significant differences in age, stature or body mass were observed. SL forwards and backs had relatively less soft tissue fat (17.5 ± 3.7 and 14.8 ± 3.6 vs. 21.4 ± 4.3 and 20.8 ± 3.8%), greater BMC (4,528 ± 443 and 4,230 ± 447 vs. 4,302 ± 393 and 3,971 ± 280 g), greater trunk lean mass (37.3 ± 3.0 and 35.3 ± 3.8 vs. 34.9 ± 32.3 and 32.3 ± 2.6 kg) and less trunk fat mass (8.5 ± 2.7 and 6.2 ± 2.1 vs. 10.7 ± 2.8 and 9.5 ± 2.9 kg) than RLC forwards and backs. Observed differences may reflect selection based on favourable physical attributes, or training adaptations. To reduce this discrepancy, some RLC players should reduce fat mass and increase lean mass, which may be of benefit for the 2015 season and beyond.

The assessment of body size and body composition is essential when evaluating and monitoring the development of Academy rugby league (RL) players. To date, no study has explored relative three-compartment body composition in Academy players compared to professional Super League (SL) players. The purpose of this study was to compare body size and relative body composition in Academy RL players and SL players using dual energy X-ray absorptiometry (DXA). With institutional research ethics approval, 63 European SL players from two clubs (backs: n = 25, age 25.7 ± 4.3 years; forwards: n = 38, age 26.1 ± 4.9 years) and 32 Academy players from one club (backs: n = 14, age 18.1 ± 1.0 years; forwards: n = 18, age 18.1 ± 0.9 years), received one total-body DXA scan (Lunar iDXA, GE Healthcare Little Chalfont, Buckinghamshire) during pre-season, in a euhydrated state (urine osmolality <700 mOsmol · kg-1). The regions of interest on scan images were manually adjusted where necessary by a qualified densitometrist, according to manufacturer guidelines. Independent t-tests compared height, body mass and percentage body fat (%BF). Multivariate analysis with height and body mass as covariates, examined positional differences in body composition by level. Effect size was calculated using Cohen’s d. SL players were taller (backs: 181.3 ± 6.1 vs. 179.5 ± 5.3 cm; forwards: 184.3 ± 5.5 vs. 179.1 ± 6.2 cm; P = 0.005, d = 0.33–0.89) and heavier (backs: 90.2 ± 9.1 vs. 83.1 ± 6.8 kg; forwards: 99.8 ± 8.1 vs. 90.1 ± 9.0 kg; P < 0.001, d = 0.88–1.13) than Academy players. %BF was greater in Academy compared to SL forwards (20.1 ± 3.0 vs. 17.5 ± 3.7%; P = 0.01, d = 0.77), but similar between levels in backs (16.1 ± 3.0 vs. 14.9 ± 3.6 %). In Academy forwards, total fat mass (FM) was greater (?3.0 (s x 0.9) kg, P = 0.009, d = 0.85), and total lean mass (LM) was lower (? -2.8 (0.9) kg, P = 0.016, d = 0.88) than in SL forwards. Relative to body size, total and regional FM, LM and BMC in Academy backs were similar to SL backs. Academy forwards had greater arm and leg FM than SL forwards (?2.7 (1.0) kg, P = 0.05, d = 0.83; ?1.7 (0.3) kg P < 0.001, d = 1.5) and lower arm (?-58.1 (16.3) g, P = 0.004, d = 1.03) and trunk (?-92.4 (31.4) g, P = 0.025, d = 0.78) BMC. Our findings of lower LM and BMC relative to body size in Academy forwards suggest that these players are still developing. This corresponds with longitudinal reports elsewhere that the majority of adult fat-free mass is achieved during the late second to early third decade, following the attainment of adult height and bone size. The longitudinal tracking of body size and composition of Academy RL players to senior level is a direction for future research.

Body composition analysis is regularly conducted in professional rugby union (RU) players to monitor changes in body mass (BM), fat mass (FM), lean mass (LM), percentage body fat (%BF) and bone mineral content (BMC). It would be desirable for RU players to maintain LM for the duration of the season, due to the high levels of muscular power and strength required for performance. To date, the seasonal changes in body composition associated with professional RU have not been documented. The purpose was to investigate acute changes in body composition during a competitive season in professional RU players using dual energy X-ray absorptiometry (DXA). With institutional ethical approval, players were recruited from an English Premiership club (n = 23, age: 25.9 ± 4.7 years, height: 187.2 ± 7.7 cm). Players received one total-body DXA scans (Lunar iDXA, GE Healthcare) during three phases of the competitive season (pre-season (August), mid-season (January) and post-season (May)) in a euhydrated state (urine osmolality

INTRODUCTION: The autonomic system and sympathetic activation appears integral in the pathogenesis of acute mountain sickness (AMS) at high altitude (HA), yet a link between heart rate variability (HRV) and AMS has not been convincingly shown. In this study we investigated the utility of the smartphone-derived HRV score to predict and diagnose AMS at HA. METHODS: Twenty-one healthy adults were investigated at baseline at 1400 m and over 10 days during a trek to 5140 m. HRV was recorded using the ithlete HRV device. RESULTS: Acute mountain sickness occurred in 11 subjects (52.4%) at >2650 m. HRV inversely correlated with AMS Scores (r = -0.26; 95% CI, -0.38 to -0.13: P < 0.001). HRV significantly fell at 3700, 4100, and 5140 m versus low altitude. HRV scores were lower in those with both mild (69.7 ± 14.0) and severe AMS (67.1 ± 13.1) versus those without AMS (77.5 ± 13.1; effect size n = 0.043: P = 0.007). The HRV score was weakly predictive of severe AMS (AUC 0.74; 95% CI, 0.58-0.89: P = 0.006). The change (delta) in the HRV Score (compared with baseline at 1400 m) was a moderate diagnostic marker of severe AMS (AUC 0.80; 95% CI, 0.70-0.90; P = 0.0004). A fall in the HRV score of >5 had a sensitivity of 83% and specificity of 60% to identify severe AMS (likelihood ratio 1.9). Baseline HRV at 1400 m was not predictive of either AMS at higher altitudes. CONCLUSIONS: The ithlete HRV score can be used to help in the identification of severe AMS; however, a baseline score is not predictive of future AMS development at HA.

Research into the physiological and movement demands of Rugby League (RL) referees is limited, with only one study in the European Super League (SL). To date, no studies have considered decision-making in RL referees. The purpose of this study was to quantify penalty accuracy scores of RL referees and determine the relationship between penalty accuracy and total distance covered (TD), high-intensity running (HIR) and heart rate per 10-min period of match-play. Time motion analysis was undertaken on 8 referees over 148 European SL games during the 2012 season using 10Hz GPS analysis and heart rate monitors. The number and timing of penalties awarded was quantified using Opta Stats. Referees awarded the correct decision on 74 ± 5% of occasions. Lowest accuracy was observed in the last 10-minute period of the game (67 ± 13%), with a moderate drop (ES= 0.86) in accuracy observed between 60-70 minutes and 70-80 minutes. Despite this, there were only small correlations observed between HRmean, total distance, HIR efforts and penalty accuracy. Although a moderate correlation was observed between maximum velocity and accuracy. Despite only small correlations observed, it would be rash to assume that physiological and movement demands of refereeing have no influence on decision-making. More likely, other confounding variables influence referee decision-making accuracy, requiring further investigation. Findings can be used by referees and coaches to inform training protocols, ensuring training is specific to both cognitive and physical match demands.

The Vendée Globe is a solo round-the-world sailing race without stopovers or assistance, a physically demanding challenge for which appropriate nutrition should maintain energy balance and ensure optimum performance. This is an account of prerace nutritional preparation with a professional and experienced female racer and assessment of daily nutritional intake (NI) during the race using a multimethod approach. A daily energy intake (EI) of 15.1 MJ/day was recommended for the race and negotiated down by the racer to 12.7 MJ/day, with carbohydrate and fluid intake goals of 480 g/day and 3,020 ml/day, respectively. Throughout the 99-day voyage, daily NI was recorded using electronic food diaries and inventories piloted during training races. NI was assessed and a postrace interview and questionnaire were used to evaluate the intervention. Fat mass (FM) and fat-free mass (FFM) were assessed pre- (37 days) and postrace (11 days) using dual-energy X-ray absorptiometry, and body mass was measured before the racer stepped on the yacht and immediately postrace. Mean EI was 9.2 MJ/day (2.4-14.3 MJ/day), representing a negative energy balance of 3.5 MJ/day under the negotiated EI goal, evidenced by a 7.9-kg loss of body mass (FM -7.5 kg, FFM -0.4 kg) during the voyage, with consequent underconsumption of carbohydrate by ~130 g/day. According to the postrace yacht food inventory, self-reported EI was underreported by 7%. This intervention demonstrates the practicality of the NI approach and assessment, but the racer's nutrition strategy can be further improved to facilitate meeting more optimal NI goals for performance and health. It also shows that evaluation of NI is possible in this environment over prolonged periods, which can provide important information for optimizing nutritional strategies for ocean racing.

Criterion data for total energy expenditure (TEE) in elite rugby are lacking, which prediction equations may not reflect accurately. This study quantified TEE of 27 elite male rugby league (RL) and rugby union (RU) players (U16, U20, U24 age groups) during a 14-day in-season period using doubly labelled water (DLW). Measured TEE was also compared to estimated, using prediction equations. Resting metabolic rate (RMR) was measured using indirect calorimetry, and physical activity level (PAL) estimated (TEE:RMR). Differences in measured TEE were unclear by code and age (RL, 4369 ± 979; RU, 4365 ± 1122; U16, 4010 ± 744; U20, 4414 ± 688; U24, 4761 ± 1523 Kcal.day-1). Differences in PAL (overall mean 2.0 ± 0.4) were unclear. Very likely differences were observed in RMR by code (RL, 2366 ± 296; RU, 2123 ± 269 Kcal.day-1). Differences in relative RMR between U20 and U24 were very likely (U16, 27 ± 4; U20, 23 ± 3; U24, 26 ± 5 Kcal.kg-1.day-1). Differences were observed between measured and estimated TEE, using Schofield, Cunningham and Harris-Benedict equations for U16 (187 ± 614, unclear; -489 ± 564, likely and -90 ± 579, unclear Kcal.day-1), U20 (-449 ± 698, likely; -785 ± 650, very likely and -452 ± 684, likely Kcal.day-1) and U24 players (-428 ± 1292; -605 ± 1493 and -461 ± 1314 Kcal.day-1, all unclear). Rugby players have high TEE, which should be acknowledged. Large inter-player variability in TEE was observed demonstrating heterogeneity within groups, thus published equations may not appropriately estimate TEE.

Prediction of adult performance from early age talent identification in sport remains difficult. Talent identification research has generally been performed using univariate analysis, which ignores multivariate relationships. To address this issue, this study used a novel higher-dimensional model to orthogonalize multivariate anthropometric and fitness data from junior rugby league players, with the aim of differentiating future career attainment. Anthropometric and fitness data from 257 Under-15 rugby league players was collected. Players were grouped retrospectively according to their future career attainment (i.e., amateur, academy, professional). Players were blindly and randomly divided into an exploratory (n = 165) and validation dataset (n = 92). The exploratory dataset was used to develop and optimize a novel higher-dimensional model, which combined singular value decomposition (SVD) with receiver operating characteristic analysis. Once optimized, the model was tested using the validation dataset. SVD analysis revealed 60 m sprint and agility 505 performance were the most influential characteristics in distinguishing future professional players from amateur and academy players. The exploratory dataset model was able to distinguish between future amateur and professional players with a high degree of accuracy (sensitivity = 85.7%, specificity = 71.1%; p<0.001), although it could not distinguish between future professional and academy players. The validation dataset model was able to distinguish future professionals from the rest with reasonable accuracy (sensitivity = 83.3%, specificity = 63.8%; p = 0.003). Through the use of SVD analysis it was possible to objectively identify criteria to distinguish future career attainment with a sensitivity over 80% using anthropometric and fitness data alone. As such, this suggests that SVD analysis may be a useful analysis tool for research and practice within talent identification.

Objectives: To retrospectively compare the longitudinal physical development of junior rugby league players between the Under 13 and 15 age categories in relation to their adult career attainment outcome.Design: Retrospective longitudinal design.Methods: Fifty-one former junior rugby league players were retrospectively grouped according to their career attainment outcome as adults (i.e., amateur, academy or professional). As juniors, players under-took a physical testing battery on three consecutive annual occasions (Under 13s, 14s, 15s) including height, body mass, sum of four skinfolds, maturation, vertical jump, medicine ball chest throw, 10–60 msprint, agility 505 and estimated VO2max. Results: Future professional players were younger than academy players with a greater estimated˙VO2max compared to amateur players. Between Under 13s and 15s, professional players (5.8 ± 2.5 cm) increased sitting height more than amateur (4.4 ± 2.1 cm) and academy (4.1 ± 1.4 cm) players. Logistic regression analyses demonstrated improvements in sitting height, 60 m sprint, agility 505 and estimated˙VO2max between amateur and professional players with a high degree of accuracy (sensitivity = 86.7%, specificity = 91.7%). Conclusions: Findings demonstrate that the development of anthropometric, maturational and physical qualities in junior rugby league players aged between 13 and 15 years contributed to adulthood career attainment outcomes. Results suggest that age, maturity and size advantages, commonly observed in adolescent focused talent identification research and practice, may not be sensitive to changes in later stages of development in order to correctly identify career attainment. Practitioners should identify, monitor and develop physical qualities of adolescent rugby league players with long-term athlete development in mind.

Purpose: This study compared the co-ingestion of glucose and fructose on exogenous and endogenous substrate oxidation during prolonged exercise at terrestrial high altitude (HA) versus sea level, in women. Method: Five women completed two bouts of cycling at the same relative workload (55% Wmax) for 120 minutes on acute exposure to HA (3375m) and at sea level (~113m). In each trial, participants ingested 1.2 g.min-1 of glucose (enriched with 13C glucose) and 0.6 g.min-1 of fructose (enriched with 13C fructose) before and every 15 minutes during exercise. Indirect calorimetry and isotope ratio mass spectrometry were used to calculate fat oxidation, total and exogenous carbohydrate oxidation, plasma glucose oxidation and endogenous glucose oxidation derived from liver and muscle glycogen. Results: The rates and absolute contribution of exogenous carbohydrate oxidation was significantly lower at HA compared with sea level (ES>0.99, P<0.024), with the relative exogenous carbohydrate contribution approaching significance (32.6±6.1 vs. 36.0±6.1%, ES=0.56, P=0.059) during the second hour of exercise. In comparison, no significant differences were observed between HA and sea level for the relative and absolute contributions of liver glucose (3.2±1.2 vs. 3.1±0.8%, ES=0.09, P=0.635 and 5.1±1.8 vs. 5.4±1.7 grams, ES=0.19, P=0.217), and muscle glycogen (14.4±12.2% vs. 15.8±9.3%, ES=0.11, P=0.934 and 23.1±19.0 vs. 28.7±17.8 grams, ES=0.30, P=0.367). Furthermore, there was no significant difference in total fat oxidation between HA and sea level (66.3±21.4 vs. 59.6±7.7 grams, ES=0.32, P=0.557). Conclusion: In women, acute exposure to HA reduces the reliance on exogenous carbohydrate oxidation during cycling at the same relative exercise intensity.

This study compared the effects of co-ingesting glucose and fructose on exogenous and endogenous substrate oxidation during prolonged exercise at altitude and sea level, in men. Seven male British military personnel completed two bouts of cycling at the same relative workload (55% Wmax) for 120 minutes on acute exposure to altitude (3375m) and at sea level (~113m). In each trial, participants ingested 1.2 g.min-1 of glucose (enriched with 13C glucose) and 0.6 g.min-1 of fructose (enriched with 13C fructose) directly before and every 15 minutes during exercise. Indirect calorimetry and isotope ratio mass spectrometry were used to calculate fat oxidation, total and exogenous carbohydrate oxidation, plasma glucose oxidation and endogenous glucose oxidation derived from liver and muscle glycogen. Total carbohydrate oxidation during the exercise period was lower at altitude (157.7±56.3 grams) than sea level (286.5±56.2 grams, P=0.006, ES=2.28), whereas fat oxidation was higher at altitude (75.5±26.8 grams) than sea level (42.5±21.3 grams, P=0.024, ES=1.23). Peak exogenous carbohydrate oxidation was lower at altitude (1.13±0.2 g.min-1) than sea level (1.42±0.16 g.min-1, P=0.034, ES=1.33). There were no differences in rates, or absolute and relative contributions of plasma or liver glucose oxidation between conditions during the second hour of exercise. However, absolute and relative contributions of muscle glycogen during the second hour were lower at altitude (29.3±28.9 grams, 16.6±15.2%) than sea level (78.7±5.2 grams (P=0.008, ES=1.71), 37.7±13.0% (P=0.016, ES=1.45). Acute exposure to altitude reduces the reliance on muscle glycogen and increases fat oxidation during prolonged cycling in men, compared with sea level.

The British Service Dhaulagiri Research Expedition took place in March-May 2016. A total of 129 personnel took part in the expedition and were invited to consent to a variety of study protocols investigating adaptation to high altitudes and diagnosis of altitude illness. The study took place in a remote and inhospitable environment at altitudes up to 7500m. This paper gives an overview of the challenges involved, the research protocols investigated and the execution of the expedition in Nepal.

Purpose: This study compared the body size and three compartment body composition between academy and senior professional rugby league players using dual energy X-ray absorptiometry (DXA). Methods: Academy (age 18.1±1.1 years; n=34) and senior (age 26.2 ±4.6 years; n=63) rugby league players received one total-body DXA scan. Height, body mass and body fat percentage alongside total and regional fat mass, lean mass and bone mineral content (BMC) were compared. Independent t-tests with Cohen’s d effect sizes and multivariate analysis of covariance (MANCOVA), controlling for height and body mass, with partial eta squared (η2) effect sizes, were used to compare total and regional body composition. Results: Senior players were taller (183.2±5.8 vs. 179.2±5.7 cm; p=0.001; d=0.70) and heavier (96.5±9.3 vs. 86.5±9.0 kg; p<0.001; d=1.09) with lower body fat percentage (16.3±3.7 vs. 18.0±3.7 %; p=0.032; d=0.46) than academy players. MANCOVA identified significant overall main effects for total and regional body composition between academy and senior players. Senior players had lower total fat mass (p<0.001, η2=0.15), greater total lean mass (p<0.001, η2=0.14) and greater total BMC (p=0.001, η2=0.12) than academy players. For regional sites, academy players had significantly greater fat mass at the legs (p<0.001; η2=0.29) than senior players. Conclusions: The lower age, height, body mass and BMC of academy players suggest that these players are still developing musculoskeletal characteristics. Gradual increases in lean mass and BMC whilst controlling fat mass is an important consideration for practitioners working with academy rugby league players, especially within the lower body.

Due to the focus of research within athletic populations, little is known about the hydration strategies of rugby league referees. We observed all 8 full-time professional referees, during 31 Super League matches to investigate the drinking strategies and magnitude of dehydration (body mass loss) experienced by referees during match play. Referees arrived and remained euhydrated (urine osmolality; pre and post-match 558 ± 310 and 466 ± 283 mOsmol•kg-1). Mean body mass change was -0.7 ± 0.8%, fluid loss was 890 ± 435 g and fluid intake was 444 ± 167, 438 ± 190, 254 ± 108 and 471 ± 221 g during pre-match, first-half, half-time and second-half. This study suggests elite referees adopt appropriate hydration strategies during match-play to prevent large reductions in body mass, although individual variability was observed. Future research should investigate dehydration in referees from other sports and the effects on refereeing performance.

Recent research has demonstrated that greater player body mass, lean mass (LM) and lower percentage body fat (%BF) are positively related to rugby league performance (e.g. Gabbett et al., 2011, Journal of Sports Sciences, 29, 1655–1664). Correspondingly, over recent years, there has been an increasing emphasis on player size and muscularity in the professional sport. However, to date, there has been no published data on the longitudinal changes in the body composition of senior professional rugby league players. Therefore, the purpose of this study was to investigate changes in three-compartment body composition over six years, in UK professional rugby league players using dual energy X-ray absorptiometry (DXA). Following institutional ethical approval, 12 professional rugby league players (baseline age: 25.0 ± 3.9 years, height: 183.4 ± 8.4 cm) from one European Super League club received total body DXA scans (Lunar iDXA, GE Healthcare) midseason in 2008 and 2014 when euhydrated (urine osmolality < 700 mOsmol · kg−1). The regions of interest on scan images were checked and manually adjusted where necessary by a qualified densitometrist according to DXA manufacturer guidelines. The primary outcomes were total body mass, %BF, total and regional fat mass (FM), LM and bone mineral content (BMC). A repeated measures multivariate analysis of variance (MANOVA), controlling for chronological age, examined differences between the two time points. Effect sizes were calculated. The repeated measures MANOVA found an overall significant effect for time (P = 0.048, = 0.99). Univariate analysis identified increases in total body mass (95.3 ± 12.2 vs. 98.5 ± 12.2 kg, P = 0.005, d = 0.26), total LM (77.2 ± 8.6 vs. 79.8 ± 9.6 kg, P = 0.006, d = 0.29) and leg LM (25.8 ± 2.8 vs. 27.6 ± 3.8 kg, P = 0.049, d = 0.54) across the six-year period. Increases were also found for total BMC (4324 ± 566 vs. 4575 ± 582 g, P < 0.001, d = 0.44) and BMC at the arms (P = 0.006, d = 0.36), legs (P = 0.001, d = 0.43) and trunk (P < 0.001, d = 0.45) regions over the six-year period. No changes were identified in %BF or FM across the six-year period. This study demonstrates that senior professional rugby league players competing in the European Super League over a six-year period have increased total body mass, which can be predominantly explained by a gain in LM of the lower body. Such findings may reflect the increasing physical demands of the professional game and a greater emphasis on lower body resistance training. These players had remained competitive in the professional sport for six years, which suggests that increasing LM and BMC may be beneficial to career longevity.

Introduction Acute exposure to very high altitude (>3500m) is associated with a suppression of appetite, acylated ghrelin (AG) and energy intake. Appetite suppression at altitude is likely caused by the reduction in arterial oxygen saturation (SpO2), consequent to the low oxygen tensions present at altitude. Beetroot juice (BRJ) has shown to minimise the altitude-related reductions in SpO2 and may therefore provide relief of altitude-induced suppression of AG and appetite. The present study investigated the effects of BRJ supplementation on appetite, AG and energy intake at 4300m simulated altitude. Methods Ten healthy males (mean(SD); age 24(7) years, body mass index 25(3)kg·m-2) completed two 6h 30mins experimental trials in normobaric hypoxia, simulating an altitude of 4300m (~11.7% FiO2). Trials were conducted in a randomised, double blind, counter-balanced fashion. After an overnight fast, participants arrived at the laboratory and completed baseline measures. Following cannulation, participants consumed a porridge breakfast accompanied by 140ml concentrated BRJ (Beet It, James White Ltd., UK) or placebo. Participants entered the hypoxic chamber 90mins after breakfast, where they rested for 2h 30mins. Participants then completed a 60min treadmill walk at 10% gradient and 50% of relative V̇O2max, whilst carrying a 10kg rucksack. After exercise, participants consumed a snack and 70ml concentrated BRJ or placebo. Participants then rested inside the chamber until 6h 30mins. After leaving the chamber, the participants were given an ad-libitum homogenous pasta meal. Fractional exhaled nitric oxide (FeNO) provided a marker of nitric oxide bioavailability. Composite appetite score (CAS) and AG were measured throughout; results are presented for four area under the curve (AUC) periods: pre-hypoxic, hypoxic rest, exercise and post-exercise. Results At baseline there were no differences in any variables between conditions (P≥0.382). There was no significant difference in FeNO between conditions upon entry to the chamber (P=0.110), however FeNO was significantly elevated in BRJ immediately prior to exercise, compared with placebo (P=0.034). There were no differences between conditions during any of the AUC periods for SpO2 (P≥0.746), AG (P≥0.231), or CAS (P≥0.730). Energy intake at the ad-libitum buffet meal did not differ between BRJ (3542±1306kJ) and placebo (3980±1342kJ; P=0.270). Discussion This study suggests that acute BRJ supplementation has no effect on appetite, AG, or energy intake at 4300m simulated altitude. However, other methodological approaches which may elevate SpO2, such as chronic BRJ loading, require further investigation.

The purpose of this study was to investigate longitudinal body composition of professional rugby union players over one competitive season. Given the potential for variability in changes, and as the first to do so, we conducted individual analysis in addition to analysis of group means. Thirty-five professional rugby union players from one English Premiership team (forwards: n = 20, age: 25.5 ± 4.7 years; backs: n = 15, age: 26.1 ± 4.5 years) received one total-body dual-energy X-ray absorptiometry (DXA) scan at preseason (August), midseason (January) and endseason (May), enabling quantification of body mass, total and regional fat mass, lean mass, percentage tissue fat mass (%TFM) and bone mineral content (BMC). Individual analysis was conducted by applying least significant change (LSC), derived from our previously published precision data and in accordance with International Society for Clinical Densitometry (ISCD) guidelines. Mean body mass remained stable throughout the season (p > 0.05), but total fat mass and %TFM increased from pre to endseason, and mid to endseason (p < 0.05). There were also statistically significant increases in total-body BMC across the season (p < 0.05). In both groups, there was a loss of lean mass between mid and endseason (p < 0.018). Individual evaluation using LSC and Bland-Altman analysis revealed a meaningful loss of lean mass in 17 players and a gain of fat mass in 21 players from pre to endseason. Twelve players had no change and there were no differences by playing position. There were individual gains or no net changes in BMC across the season for 10 and 24 players, respectively. This study highlights the advantages of an individualised approach to DXA body composition monitoring and this can be achieved through application of derived LSC.

This study investigated the change in body composition and bone mineral content (BMC) of senior rugby league players between 2008 and 2014. Twelve male professional rugby league players (age, 24.6±4.0 years; stature, 183.4±8.4 cm) received a DXA scan during pre-season in 2008 and 2014. Between 2008 and 2014, very likely increases in leg lean mass, total trunk and leg BMC, and a likely increase in arm BMC and possible increases in body mass, total and trunk fat mass, and total, trunk and arm lean mass were observed. Unlikely decreases and unclear changes in leg and arm fat mass were also found. Large negative correlations were observed between age and body mass (r=-0.72), lean mass (r=-0.70), fat mass (r=-0.61), and BMC (r=-0.84) change. Three participants (19.1 ± 1.6 years) increased lean mass by 7.0 – 9.3 kg. Younger players had the largest increases in lean mass during this period, although an older player (30 year-old) still increased lean mass. Differences in body composition change were also observed for participants of the same age, thus contextual factors should be considered. This study demonstrates the individuality of body composition changes in senior professional rugby players, while considering the potential change in young athletes.

Purpose Circulating acylated ghrelin concentrations are associated with altitude-induced anorexia in laboratory environments, but have never been measured at terrestrial altitude. This study examined time course changes in appetite, energy intake, body composition, and ghrelin constituents during a high-altitude trek. Methods Twelve participants [age: 28(4) years, BMI 23.0(2.1) kg m−2] completed a 14-day trek in the Himalayas. Energy intake, appetite perceptions, body composition, and circulating acylated, des-acylated, and total ghrelin concentrations were assessed at baseline (113 m, 12 days prior to departure) and at three fixed research camps during the trek (3619 m, day 7; 4600 m, day 10; 5140 m, day 12). Results Relative to baseline, energy intake was lower at 3619 m (P = 0.038) and 5140 m (P = 0.016) and tended to be lower at 4600 m (P = 0.056). Appetite perceptions were lower at 5140 m (P = 0.027) compared with baseline. Acylated ghrelin concentrations were lower at 3619 m (P = 0.046) and 4600 m (P = 0.038), and tended to be lower at 5140 m (P = 0.070), compared with baseline. Des-acylated ghrelin concentrations did not significantly change during the trek (P = 0.177). Total ghrelin concentrations decreased from baseline to 4600 m (P = 0.045). Skinfold thickness was lower at all points during the trek compared with baseline (P ≤ 0.001) and calf girth decreased incrementally during the trek (P = 0.010). Conclusions Changes in plasma acylated and total ghrelin concentrations may contribute to the suppression of appetite and energy intake at altitude, but differences in the time course of these responses suggest that additional factors are also involved. Interventions are required to maintain appetite and energy balance during trekking at terrestrial altitudes.

Purpose: Nitric oxide (NO) bioavailability is reduced during acute altitude exposure, contributing towards the decline in physiological and cognitive function in this environment. This study evaluated the effects of nitrate (NO3-) supplementation on NO bioavailability, physiological and cognitive function, and exercise performance at moderate and very-high simulated altitude. Methods: Ten males (mean (SD): V̇O2max: 60.9 (10.1) ml·kg-1·min-1) rested and performed exercise twice at moderate (~14.0 % O2; ~3000 m) and twice at very-high (~11.7% O2; ~4300 m) simulated altitude. Participants ingested either 140 ml concentrated NO3--rich (BRJ; ~12.5 mmol NO3-) or NO3--deplete (PLA; 0.01 mmol NO3-) beetroot juice 2 hours before each trial. Participants rested for 45 minutes in normobaric hypoxia prior to completing an exercise task. Exercise comprised a 45 minute walk at 30 % V̇O2max and a 3 km time-trial (TT), both conducted on a treadmill at a 10 % gradient whilst carrying a 10 kg backpack to simulate altitude hiking. Plasma nitrite concentration ([NO2-]), peripheral oxygen saturation (SpO2), pulmonary oxygen uptake (V̇O2), muscle and cerebral oxygenation, and cognitive function were measured throughout. Results: Pre-exercise plasma [NO2-] was significantly elevated in BRJ compared with PLA (p = 0.001). Pulmonary V̇O2 was reduced (p = 0.020), and SpO2 was elevated (p = 0.005) during steady-state exercise in BRJ compared with PLA, with similar effects at both altitudes. BRJ supplementation enhanced 3 km TT performance relative to PLA by 3.8 % (1653.9 (261.3) vs. 1718.7 (213.0) s) and 4.2 % (1809.8 (262.0) vs. 1889.1 (203.9) s) at 3000 m and 4300 m, respectively (p = 0.019). Oxygenation of the gastrocnemius was elevated during the TT consequent to BRJ (p = 0.011). The number of false alarms during the Rapid Visual Information Processing Task tended to be lower with BRJ compared with PLA prior to altitude exposure (p = 0.056). Performance in all other cognitive tasks did not differ significantly between BRJ and PLA at any measurement point (p ≥ 0.141). Conclusion: This study suggests that BRJ improves physiological function and exercise performance, but not cognitive function, at simulated moderate and very-high altitude

Product Description Whether you’re an experienced mountaineer, a hardened climber, or about to embark on your first expedition, nothing is more critical than anticipating, understanding, and preparing for the adversities and accomplishments that await you and your team. In Mountaineering: Training and Preparation, Carlton Cooke, Dave Bunting, and John O’Hara, along with the members of the British Army Everest West Ridge Expedition team and sport and exercise scientists from Leeds Metropolitan University, share their insights, experiences, and expertise on these aspects of mountaineering: •Selecting the right team for each expedition •Physical conditioning and training programs to ensure success •Nutritional strategies for your training and expeditions •Team safety, climbing precautions, and first aid •Preparing for and surviving in extreme conditions From the technical aspects of a climb to the leadership and teamwork skills so essential to success, this comprehensive guide covers all of the essentials for a safe and successful expedition. Mountaineering: Training and Preparation is must-read for every mountaineer. Read it before your next expedition. Contents Part I Planning and Team Selection Chapter 1 Logistics and Planning Chapter 2 Team Selection Chapter 3 Preparation Chapter 4 Equipment Chapter 5 First Aid, Travel, and Acclimatisation Part II Conditioning and Nutrition for Expeditions Chapter 6 Fitness and Training Chapter 7 Endurance Training Chapter 8 Strength and Power Training Chapter 9 Nutrition for Training Chapter 10 Nutrition for Expeditions Part III Expedition Leadership and Psychology Chapter 11 Psychological Skills in the Outdoors Chapter 12 Resilience Chapter 13 Leadership

Purpose This study examined the influence of dynamic apnoea training on splenic volume and haematological responses in non-breath-hold divers (BHD). Methods Eight non-BHD performed ten maximal dynamic apnoeas, four times a week for six weeks. Splenic volumes were assessed ultrasonically, and blood samples were drawn for full blood count analysis, erythropoietin, iron, ferritin, albumin, protein and osmolality at baseline, 24 h post the completion of each week’s training sessions and seven days post the completion of the training programme. Additionally, blood samples were drawn for haematology at 30, 90, and 180 min post session one, twelve and twenty-four. Results Erythropoietin was only higher than baseline (6.62 ± 3.03 mlU/mL) post session one, at 90 (9.20 ± 1.88 mlU/mL, p = 0.048) and 180 min (9.04 ± 2.35 mlU/mL, p = 0.046). Iron increased from baseline (18 ± 3 µmol/L) post week five (23 ± 2 µmol/L, p = 0.033) and six (21 ± 6 µmol/L; p = 0.041), whereas ferritin was observed to be lower than baseline (111 ± 82 µg/L) post week five (95 ± 75 µg/L; p = 0.016), six (84 ± 74 µg/L; p = 0.012) and one week post-training (81 ± 63 µg/L; p = 0.008). Reticulocytes increased from baseline (57 ± 12 × 109/L) post week one (72 ± 17 × 109/L, p = 0.037) and six (71 ± 17 × 109/L, p = 0.021) while no changes were recorded in erythrocytes (p = 0.336), haemoglobin (p = 0.124) and splenic volumes (p = 0.357). Conclusions Six weeks of dynamic apnoeic training increase reticulocytes without altering mature erythrocyte concentration and splenic volume.

To advance our understanding of talent identification and development (TID), it is valuable to retrospectively trace athletes’ long-term career progression (Vaeyens et al., 2008, Journal of Sports Sciences, 38, 703–714). However, research monitoring athletes’ career progression through TID programmes into professional sport is limited, and no study has assessed career outcomes based on a retrospective longitudinally tracked sample. Therefore, the purpose of this study was to retrospectively compare the anthropometric and performance characteristics of junior rugby league players consecutively selected to a TID programme over 3 years (Under 13s, 14s and 15s) in relation to their longterm career progression. With local institutional ethics approval, former junior rugby league players were grouped according to their long-term career progression level (i.e., amateur, n = 12; academy, n = 24; professional, n = 15). All players undertook anthropometric (height, body mass, sum of four skinfolds), maturational (age at peak height velocity) and performance (vertical jump, medicine ball chest throw, 10–60 m sprint, agility 505 and estimated V?O2max via the multistage fitness test) assessments at the Under 13–15 age categories. A repeated measures multivariate analysis of variance identified overall significant effects for time (P < 0.001; ?2 = 1.00), career level (P = 0.005; ?2 = 0.48) and career level × time (P = 0.049; ?2 = 0.73). More specifically, univariate analysis identified differences at the junior age groups between career levels for chronological age (P = 0.002; ?2 = 0.24) and estimated V? O2max (P = 0.006; ?2 = 0.19), with professional players significantly younger than academy players and professional players having higher estimated V? O2max compared to amateur players. Significant interactions for career level × time were apparent for sitting height (P = 0.049; ?2 = 0.11), body mass (P = 0.05; ?2 = 0.09), 10-m sprint (P = 0.023; ?2 = 0.11) and 20-m sprint (P = 0.018; ?2 = 0.12). Greater increases in sitting height and body mass were observed for professional compared to amateur players. For sprint speed, greater improvements in performance were observed in amateur and professional compared to academy players. This study demonstrates, based on group responses, that future professional players selected to a TID programme were younger with a greater V? O2max and increased sitting height and body mass more than amateur players over a 2-year period (Under 13s-–15s). Such findings demonstrate that age and size advantages commonly observed in TID research within adolescent athletes may not be sensitive indicators to correctly identify future career progression. It is recommended that the evaluation of adolescent athletes within TID programmes should incorporate monitoring the development of anthropometric and performance characteristics over time instead of (de)selecting players using one-off assessments.

We investigated 3-compartment body composition across one competitive season in professional male rugby union players using dual-energy X-ray absorptiometry (GE iDXA). Thirty five players from one English Premiership team (forwards: n=20, age: 25.5±4.7 years; backs: n=15, age: 26.1±4.5 years) received one total body DXA scan at pre-season (August), mid-season (January) and end-season (May), enabling quantification of body mass, total and regional fat mass, lean mass, percentage tissue fat mass (%TFM) and bone mineral content (BMC). Both team and individual changes were evaluated, and for the latter, least significant change (LSC) was derived from precision data and applied as per International Society for Clinical Densitometry guidelines. Mean body mass remained stable throughout the season (p>0.05), but total fat mass and %TFM increased from pre to end-season, and mid to end-season (p<0.05). There were also statistically significant increases in total-body BMC across the season (P<0.05). In backs, there was a loss of lean mass between mid and end-season (P<0.01). Individual evaluation using LSC and Bland Altman analysis revealed a meaningful loss of lean mass in 17 players and a gain of fat mass in 21 players from pre to end-season. Twelve players exhibited no change. Strategies to improve the maintenance of pre-season lean/ fat ratios across the season for professional rugby union players might be beneficial to performance and health, and thus require exploration. We recommend that future studies include an individualised approach to DXA body composition monitoring and this can be achieved through application of derived LSC.