Dr Gareth Nicholson

Females are 2–10 times more likely to suffer an anterior cruciate ligament (ACL) tear than their male counterparts (Russell et al., 2005, Journal of Athletic Training, 41, 166–171). Despite the apparent gender difference in injury occurrence, ambiguity still exists regarding the underlying mechanisms, with most studies investigating only one or two potential factors. Hence, the purpose of this study was to investigate the effects of gender on a host of lower limb injury risk factors. Following institutional ethical approval, six male (21.0 ± 3.16 years, 181.4 ± 3.79 cm, 91.0 ± 5.44 kg) and six female (20.33 ± 0.82 years, 166.18 ± 6.61 cm, 68.02 ± 4.61 kg) (mean ± SD) participants completed two testing sessions separated by at least 48 h. During visit one, the participants performed maximal contractions (×3) of an isokinetic knee extension/flexion exercise on a Cybex dynamometer at velocities of 0.52 rad · s−1 and 4.19 rad · s−1 . On the second visit, maximal bilateral and unilateral countermovement (×3) and drop jump (×3) trials were performed on a force platform (Kistler, 1000 Hz) with lower-body kinematics being concurrently recorded in the frontal plane using a high speed video camera (Fastec TS3-39, 100 Hz). Independent t-tests examined gender differences in performance (P < 0.05) and Pearson’s correlations (two-tailed) examined relationships between isokinetic performance and lower-body jumping kinematics. Females (4.77° ± 14.20°) displayed significantly greater knee valgus on landing from a bilateral drop jump than males (−15.82° ± 10.49°, P < 0.05). Importantly, knee valgus during the stance phase of the drop jump displayed a significant negative correlation with concentric hamstring-to-quadriceps ratio (H:Q ratio) at 0.52 rad · s−1 (r = −0.60, P < 0.05). There was a tendency for females (51.83 ± 6.85% and 53.83 ± 6.85%) to display lower H:Q ratios than males (56.83 ± 55.42% and 58.17 ± 10.07%) at 0.52 rad · s−1 and 4.19 rad · s −1, respectively; however, this was not statistically significant. Furthermore, there were no significant differences in leg dominance between males and females (P > 0.05). Despite the higher knee injury incidence in females, significant differences were only observed between males and females in landing kinematics during jumping tasks. Present findings suggest that knee joint kinematics adopted by females may be partially explained by quadriceps dominant characteristics. Although the link between knee joint kinematics and ACL injuries requires further investigation, the present findings highlight that examination of two-dimensional knee joint kinematics during jumping assessments may provide a useful means of identifying potential injury risk factors for coaches working in an applied setting.

Aims The ideal management of acute syndesmotic injuries in elite athletes is controversial. Among several treatment methods used to stabilize the syndesmosis and facilitate healing of the ligaments, the use of suture tape (InternalBrace) has previously been described. The purpose of this study was to analyze the functional outcome, including American Orthopaedic Foot & Ankle Society (AOFAS) scores, knee-to-wall measurements, and the time to return to play in days, of unstable syndesmotic injuries treated with the use of the InternalBrace in elite athletes. Methods Data on a consecutive group of elite athletes who underwent isolated reconstruction of the anterior inferior tibiofibular ligament using the InternalBrace were collected prospectively. Our patient group consisted of 19 elite male athletes with a mean age of 24.5 years (17 to 52). Isolated injuries were seen in 12 patients while associated injuries were found in seven patients (fibular fracture, medial malleolus fracture, anterior talofibular ligament rupture, and posterior malleolus fracture). All patients had a minimum follow-up period of 17 months (mean 27 months (17 to 35)). Results All patients returned to their pre-injury level of sports activities. One patient developed a delayed union of the medial malleolus. The mean return to play was 62 days (49 to 84) for isolated injuries, while the patients with concomitant injuries returned to play in a mean of 104 days (56 to 196). The AOFAS score returned to 100 postoperatively in all patients. Knee-to-wall measurements were the same as the contralateral side in 18 patients, while one patient lacked 2 cm compared to the contralateral side. Conclusion This study suggests the use of the InternalBrace in the management of unstable syndesmotic injuries offers an alternative method of stabilization, with good short-term results, including early return to sports in elite athletes.

Falls are a significant ongoing public health concern for older adults. At present, few studies have concurrently explored the influence of multiple measures when seeking to determine which variables are most predictive of fall risks. As such, this cross-sectional study aimed to identify those functional variables (i.e. balance, gait and clinical measures) and physical characteristics (i.e. strength and body composition) that could best distinguish between older female fallers and non-fallers, using a machine learning approach. Overall, 60 community-dwelling older women (≥65 years), retrospectively classified as fallers (n = 21) or non-fallers (n = 39), attended three data collection sessions. Data (281 variables) collected from tests in five separate domains (balance, gait, clinical measures, strength and body composition) were analysed using random forest (RF) and leave-one-variable-out partial least squares correlation analysis (LOVO PLSCA) to assess variable importance. The strongest discriminators from each domain were then aggregated into a multi-domain dataset, and RF, LOVO PLSCA, and logistic regression models were constructed to identify the important variables in distinguishing between fallers and non-fallers. These models were used to classify participants as either fallers or non-fallers, with their performance evaluated using receiver operating characteristic (ROC) analysis. The study found that it is possible to classify fallers and non-fallers with a high degree of accuracy (e.g. logistic regression: sensitivity = 90%; specificity = 87%; AUC = 0.92; leave-one-out cross-validation accuracy = 63%) using a combination of 18 variables from four domains, with the gait and strength domains being particularly informative for screening programmes aimed at assessing falls risk.

Background: Falls are a significant public health concern for older adults, and are associated with many detrimental physical, psychological and economic consequences. The aim of this thesis was to identify which functional variables (i.e. balance, gait and clinical measures) and physical characteristics (i.e. strength and body composition) could best distinguish between older female fallers and non-fallers, using a novel machine learning approach. Methods: 60 community-dwelling older women (≥65 years), classified as fallers and non-fallers based on falls history, attended three data collection sessions. Centre of pressure data were collected during five static posturography protocols. Ground reaction force (GRF) and kinematic data were measured during walking trials at two gait speeds. Participants completed five clinical measures, and strength assessments were performed at the trunk, knee and ankle for both limbs using an isokinetic dynamometer. Dual energy X-ray absorptiometry scans were conducted to assess body composition, bone mineral density and hip structure. The data (281 variables) were partitioned into five data packages (balance, gait, clinical measures, strength and body composition) and a uniform analysis strategy was applied to each in the single-domain analyses. Random forest and leave-one-variable-out partial least squares correlation analysis were employed to assess variable importance. The important variables selected were combined into two refined datasets, and classification models were constructed to differentiate between fallers and non-fallers. Subsequently, the strongest discriminators from each data package were compiled and analysed in the multi-domain analyses using the same strategy. Findings: Overall, this thesis demonstrates that it is possible to distinguish between fallers and non-fallers with a high degree of accuracy, using a refined set of variables and a sophisticated multivariate approach, in both a single- and multi-domain context. Important balance, gait, clinical measures, strength, and body composition variables were identified for discriminating between groups, alongside redundant factors. In the balance data package, multiple variables measured during the limits of stability, unilateral stance, and Modified Clinical Test of Sensory Interaction on Balance were identified as important discriminators. In the gait data package, a combination of spatiotemporal, kinematic, GRF, and variability variables were selected as important. In the clinical measures data package, several variables measured during the Timed Up and Go, Tinetti Performance Oriented Mobility Assessment, and gait speed protocols appeared useful when differentiating between groups. In the strength data package, a combination of peak torque variables, namely knee flexion, dorsiflexion and plantar flexion, alongside three asymmetry variables were identified as important. In the body composition data package, several muscle quality indices were selected as important. In the multi-domain data package, a combination of gait, clinical measures, strength, and body composition variables appeared to be the most important discriminators between fallers and non-fallers. This study is one of the few comprehensive analyses to include important variables from multiple domains with a sophisticated machine learning approach. The findings can be used to inform the design of optimal falls screening and prevention methods. Furthermore, this work highlights the applicability of machine learning techniques when investigating falls in older women.

The purpose of the study was to investigate the magnitude of bilateral deficit (BLD) in trained males and examine its relationship with functional performance and recent resistance training history. Ten physically active males (age: 23.02±1.27 years) self-reported the number of unilateral and bilateral exercises within their structured resistance training schedule. During two visits to the laboratory, participants performed unilateral and bilateral squat jumps (SJ) and isometric leg extensions (ILE) for the quantification of BLD. Participants also performed bilateral countermovement jumps (CMJ) and a change of direction (COD) test to quantify functional performance. The performance outcomes and information regarding training history were then correlated with the bilateral index (BLI) metric. The key findings were that: (a) a lower BLD in SJ peak power related to a greater CMJ peak force (r=.728; p=.02) and peak power (r=.750; p=.01), (b) the BLI in the ILE was unrelated to performance outcomes, and (c) BLI was unrelated to the mean number of bilateral and unilateral exercises in the structured resistance training programme of participants. In conclusion, lower levels of BLD may be advantageous for bilateral tests of functional performance (i.e. jumps) however there is a need to consider the mechanical similarity between the performance and BLD measure. Finally, the balance of unilateral and bilateral exercises in an individual’s recent resistance training history is not sensitive to the BLI measured during dynamic or isometric assessments.

BACKGROUND AND AIM:Age-related declines in muscle strength have been associated with reduced functional capacity, postural instability and increased risk of falls in older adults. Studies have generally focussed on the significance of lower limb strength, however more recently the importance of trunk muscle strength has been explored, which may have been previously overlooked (Granacher et al., 2013). A limited number of studies have investigated the relationship between trunk strength and function, but this was tested under isometric contractions(Shahtahmassebi et al., 2017). Therefore, the purpose of this study was to investigate the relationship between dynamic (concentric) trunk strength and functional mobility in older women. METHODS:A sample of 40 older women (age: 68.9±3.73 years) participated in this study. To assess functional mobility, participants completed the timed up and go (TUG), 30 second chair stand test (CST), and a timed stair climb task (ascent and descent). Both self-selected normal and fast gait speed (GS) were also recorded. Concentric trunk flexion and extension strength data were collected using an isokinetic dynamometer (Biodex, USA). Measurements were conducted in the seated-compressed position in line with the manufacturer's guidelines. Following five sub-maximal trials, peak torque was recorded during three maximal flexion and extension trials at two testing speeds (20°/s and 45°/s). Peak torque was then normalised to body mass. Pearson's correlations were performed to investigate relationships between trunk strength and functional mobility measures. The level of significance was set at p≤0.05. RESULTS:A number of associations between trunk strength and functional mobility measures were revealed. Greater trunk extension strength was correlated with superior performance in the CST (45°/s: r=0.33, p=0.037), stair ascent (20°/s: r=-0.32, p=0.043; 45°/s: r=-0.56, p=<.001) and stair descent tasks (45°/s: r=-0.47, p=0.002). Trunk extension strength was also associated with GS during normal (20°/s: r=0.37, p=0.019; 45°/s: r=0.48, p=0.004) and fast trials (45°/s: r=0.34, p=0.034). Trunk flexion strength was correlated with TUG (45°/s: r=-0.42, p=0.007), stair ascent (20°/s: r=-0.41, p=0.008; 45°/s: r=-0.47, p=0.002) and stair descent times (20°/s: r=-0.44, p=0.005; 45°/s: r=-0.42, p=0.007). Trunk flexion strength was also associated with normal (20°/s: r=0.55, p=<.001; 45°/s: r=0.56, p=<.001) and fast GS (20°/s: r=0.32, p=0.047; 45°/s: r=0.34, p=0.031). CONCLUSIONS: These findings suggest that there is a moderate-strong relationship between muscle strength in the trunk area and a range of functional mobility measures in older women. These results have important practical implications which could be used to inform the inclusion of trunk exercises in interventions targeting functional mobility for older adults.

Introduction: Considering a) that the ‘learning effect’ in isokinetic assessments may impact on a clinician’s ability to detect genuine changes in muscle function and b) the rare nature of constant velocity movements in daily activities, it becomes apparent that familiarisation is key to optimising the reproducibility of measurements. This study examined the impact of testing protocols which differed in repetition number and rest intervals on the stability of isokinetic and isometric measurements conducted on the knee extensors and flexors across multiple testing sessions. Methods: 12 males (age: 23.3 ± 1.6 years; height: 1.80 ± 0.06 m; mass: 83.2 ± 9.6 kg) were randomly divided into a LONG and SHORT group and completed 6 group-specific testing sessions (48-96 hours rest between visits) which involved maximal isokinetic (30o/s, 90o/s, 180o/s) and isometric repetitions (extensors: 70o - flexors: 50o) in seated and prone positions on a Cybex NORM dynamometer. The LONG protocol involved 70 submaximal and 36 maximal repetitions and a total resting time of 3140s whereas the SHORT included 40 submaximal and 24 maximal repetitions with a total resting time of 2360s. A range of statistical techniques including measures of reliability were employed. Results: Overall the LONG group exhibited higher torque values (+10-25%) for extensors and flexors under both isokinetic and isometric conditions. However, a mixed-design ANOVA revealed no main effects for each factor (group, visit) nor any significant interaction. Intraclass Correlation Coefficients (ICCs) for the isokinetics did not show any trend between visits but generally the LONG protocol produced consistently ICCs over 0.90 (mean ICC: LONG = 0.92 vs SHORT = 0.83). LONG group values for Standard error of measurement, Typical error, Limits of agreement and Coefficients of variation were slightly better than SHORT. The LONG protocol produced better reliability for the isometric extensors torque (ICC: 0.93 vs 0.67) but the SHORT for the flexors (ICC: 0.78 vs 0.95). Discussion: A single visit can produce similar results as repeat visits providing a conventional protocol is applied and strict adherence to testing principles (stabilisation, instructions, feedback) is ensured. Two sessions may be adequate to “learn” the movements and reach a satisfactory degree of performance stability. However, a longer protocol comprising an increased number of submaximal-maximal trials (≥ 20 per speed) supplemented by rest intervals of 30-90s (between repetitions-speeds) and 10min between positions, and a prone position for leg flexors can offer additional reliability. Ultimately, the exact level of acceptable reproducibility is always decided by the researcher after considering sample characteristics and type of application.

The Achilles tendon is the most frequently ruptured tendon in the body with an annual incidence of 21 ruptures per 100,000 individuals per year (Lantto et al., 2015). Achilles tendon rupture is highest in middle-aged people (40-50 years) and males are more frequently affected the females (Lawrence et al., 2017). In the last decade, there has been an increasing amount of literature investigating non-operative management of Achilles tendon tears (Hutchinson et al., 2015). There is an ongoing debate regarding the optimum management method for Achilles tendon ruprtures, however, much of the research focuses on complications following treatment such as tendon re-rupture. Very little information exists regarding the functional outcomes of treatment which is needed to manage patient expectations regarding return to activity and long-lasting functional impairments (Khan et al., 2005). Very recent research has examined the longer term functional outcomes of Achilles tendon ruptures using more sophisticated measures (e.g. strength assessments), however this research has focused on the outcomes of non-operative management (Lawrence et al., 2017). As a result, this study aims to examine the neuromuscular and functional outcomes of operatively managed ruptures using sophisticated measures such as ultrasound and gait analysis.

This study compared angle-specific hamstring:quadricep (H:Q) ratios with their discrete counterparts during strength testing in pro fessional male footballers. Twenty-eight professional English Premier League footballers were recruited for this study (age: 22 6 4 years; stature: 1.81 6 0.07 m; body mass: 75.2 6 6.8 kg). Isokinetic testing of the knee flexors and extensors was conducted concentrically at 2 angular velocities (60˚ and 240˚·s21 ) and eccentrically (for the knee flexors only) at 30˚·s21 . Conventional H:Q ratio was calculated as the ratio between peak joint moment in the flexors and extensors at 60˚·s21 . Functional H:Q ratio was calculated as the peak joint moment in the flexors during the eccentric condition and the extensors at 240˚·s21 . Discrete conventional and functional H:Q ratios were 0.56 6 0.06% and 1.28 6 0.22%, respectively. The residual differences between discrete values and angle-specific residual values were 13.60 6 6.56% when normalized to the magnitude of the discrete value. For the functional ratios, the normalized residual was 21.72 6 5.61%. Therefore, neither discrete ratio was representative of angle-specific ratios, although the conventional ratio had lower error overall. Therefore, practitioners should consider H:Q ratio throughout the full isokinetic range of motion, not just the discrete ratio calculated from peak joint moments, when designing and implementing training programs or monitoring injury risk, recovery from injury, and readiness to return to play

Objectives: Achilles tendon rupture leads to functional impairments and these may be underpinned by morphological changes in the muscle-tendon unit. Functional performance of the injured limb will be impaired regardless of time since surgery and these impairments occur alongside changes in muscle-tendon morphology. Methods: Following operative treatment of Achilles tendon rupture and short term immobilisation, 12 patients completed a battery of tests during a single visit to the laboratory (performed an average of 4.4 ± 2.6 years post-surgery). Patients completed the Achilles’ tendon rupture score (ATRS), tests of ankle and hip range of motion (ROM) and ultrasound measurements of muscle-tendon architecture. Data on isokinetic (30 o/s, 60 o/s) plantar flexion strength, jumping performance and walking-running were also collected on the same visit. Percentage deficits were expressed relative to the non-injured limb and determined for statistical significance (p < 0.05). Relationships between outcomes measures and time since surgery were tested using Pearson’s correlation coefficients (p < 0.05). Results: The repaired limb showed a shorter muscle fascicle length (12.1-19.6%), increased fascicle pennation (18.0±22.14%) and reduced muscle thickness (9.1-20.1%) in the gastrocnemius and/or soleus along with greater tendon cross-sectional area (46.7±34.47%). Functionally, the repaired limb displayed lower countermovement jump height (-12.6±15.68%) and longer drop jump contact times (5.5±5.7%). Also, the repaired limb showed reduced hip internal-external ROM (6.3±8.2%) but no differences existed between limbs for plantar flexion ROM and strength or gait characteristics. Good ATRS outcomes were reported (mean: 87.9±16.2, range: 43-100) which related to time since surgery (r=0.79) but individual ATRS items did not correlate with corresponding objective measures. Conclusion: Plantar flexor atrophy following surgically treated Achilles tendon rupture is partially compensated for by remodelling of the fascicles however, impairments may still persist many years into the postoperative period although these may be more pronounced in high-velocity activities.

This report provides a detailed analysis of the women's final, including key parameters during the approach, take off and bar clearance. The full report is available from the IAAF website: https://www.iaaf.org/about-iaaf/documents/research

The use of multi-joint isometric assessments, particularly the back squat, is becoming increasingly more common in an attempt to increase the ecological validity of research. Surprisingly, no strong consensus exists regarding the optimal knee angle during such assessments with previous investigations using angles ranging from 30° to 170° (e.g., Marcora and Miller, 2000, Journal of Sports Sciences, 18, 313–310). The purpose of this study was therefore to examine the effect of knee joint angle on the between-session reproducibility of the maximal isometric back squat. Following ethical approval, seven trained males (24.29 ± 4.23 years) completed four identical testing sessions in a 48 hour test-retest design. The sessions comprised a warm-up, two practice and three maximal isometric back squats performed using a squat rack positioned over a Kistler force platform (1000 Hz). The trials were performed at knee angles of 90°, 100°, 110° and 130° with the same two angles being used in sessions 1 and 2 and the remaining two angles forming sessions 3 and 4. Peak force was identified from the resultant force–time curves with the best trial carried forward for statistical analysis. Three methods of assessing reproducibility were used after the data were assessed for heteroscedasticity: 95% limits of agreement (LOA), coefficient of variation (CV) and intraclass correlation coefficient (ICC). CV showed a higher level of reproducibility when peak force was measured at 100° (CV: 2.93%) and 110° (CV: 1.93%) when compared to measurements taken at 90° (4.13%) and 130° (3.05%). The absolute reliability statistics revealed a similar trend with measurements at 110° demonstrating a high level of reproducibility as shown by a % bias of 2.57%, a random error of 5.14%. Measurements at 90° and 130° demonstrated a notably lower level of reproducibility, with the 90° knee angle in particular being characterised by a higher bias (6.32%), notable levels of random error (18.53%) and LOA of 232.61 ± 472.84 N (bias ± random error). Although a number of previous investigations (e.g., Demura et al., 2010, Journal of Strength & Conditioning Research, 24, 2742–2748) have chosen a knee angle of 90° for the isometric back squat based on positions adopted during dynamic performance, unacceptable levels of variability were observed when measurements were made at this angle. The present findings underline that measurements made at 110° knee flexion provide the greatest level of reproducibility for use during separate sessions. Such information may assist practitioners when selecting testing batteries aimed at quantifying improvements following training interventions.

This report provides a detailed analysis of the men's final, including key parameters during the approach, take off and bar clearance. The full report is available from the IAAF website: https://www.iaaf.org/about-iaaf/documents/research

This report provides a detailed analysis of the men's final, including key parameters during the approach, take off and bar clearance. The full report is available from the IAAF website: https://www.iaaf.org/about-iaaf/documents/research

Introduction: Whilst high-speed motion analysis systems represent the preferred method of assessing barbell kinematics during resistance exercise, it is now possible to attach an accelerometer to the barbell to gain immediate feedback. Although some studies support the validity of accelerometers, others have found below-standard accuracy and reliability compared to laboratory-based measures (McCurdy et al. 2011). Thus the purpose of this study was to examine the validity of two tri-axial accelerometers for measuring the mechanical characteristics of the back squat exercise. Methods: Ten trained males (22.2 ± 3.4 years) completed a single testing session involving a standardised warm-up and 4 single repetitions of the back squat (80% training maximum). A force platform (FP, 1000 Hz) and Qualysis motion capture system (QL, 250 Hz) were used to examine the mechanical characteristics of the repetitions as well as a Kistler (A1, 1000 Hz) and Myotest Pro (A2, 250 Hz) accelerometer mounted on the barbell. The FP, QL and A1 systems were telemetrically synchronised, this allowed peak vertical power (PP), velocity (PV), force (PF) and acceleration (PA) to be compared. Three methods of assessing the agreement between the systems were then used after the data were assessed for heteroscedasticity: 95% Limits of Agreement (LOA), Coefficient of Variation (CV) & Intraclass Correlation Coefficient [(3,1) consistency]. Results: Comparisons between the barbell and FP measures were characterised by high levels of systematic bias, random error and poor ICC’s for all of the variables analysed. The comparison between FP and A2 for PV was particularly indicative of the overall trend with a bias of 10.49%, a random error of 94.61% and an ICC of 0.48. Furthermore, A2 overestimated PF by 1.79%, PP by 9.41% and PV by 11.07% when compared to FP. Importantly, a poor level of agreement was also observed between the barbell measures for PP, PV and PA when interpreted using all reliability statistics. The comparison between QL and A2 for PV was particularly indicative of the overall trend with a bias of 5.25%, a random error of 84.90% and an ICC of 0.53. Discussion: Whilst the lack of agreement between the accelerometer and FP measures most likely reflects the difference between barbell and full-body kinematics, A1 and A2 did not display adequate agreement with a laboratory measure of barbell kinematics for the majority of variables analysed. Based on the fact that the acceleration-time curves followed a similar pattern, there may be some scope for coaches to gain some valuable information from accelerometry. However, from a research perspective the present findings question the accuracy of tri-axial accelerometry for examining barbell kinematics during the back squat exercise.

Introduction: A typical kinetic analysis of countermovement jump performance (CMJ) usually involves the calculation of performance variables such as jump height, power & velocity. However further levels of analysis can offer advanced variables which may reveal important information about mechanical mechanisms underlying performance changes (Cormie et al. 2009) providing these advanced variables exhibit satisfactory between-session reproducibility. Hence, this study aimed a) to identify new mechanical variables associated with CMJ performance and b) to quantify their reproducibility using a range of reliability statistics. Methods: Seven males (23.6 ± 2.7 years) accustomed with jumping activities completed 2 identical testing sessions separated by 48 hrs. The sessions comprised a dynamic warm-up, 2 practice & 3 maximal CMJ’s performed on a force plate (1000Hz). Jump height (JH) was calculated via the flight time method & 68 other variables were derived from the force-time curves. Pearson correlation coefficients were calculated to determine associations with JH. Three methods for assessing reliability were also used after the data were assessed for heteroscedasticity: 95% Limits of Agreement (LOA), Coefficient of Variation (CV) & Intraclass Correlation Coefficient [(3,1) consistency]. Results: Out of the 68 variables analysed, 25 correlated significantly with JH (p≤0.05). Although 11 of these variables (e.g. power & velocity) were derived from the initial level of analysis, 14 of the advanced variables also displayed significant correlations. 51 of the 68 variables showed acceptable levels of reproducibility, these were derived from the initial and advanced levels of analysis. A key variable such as the duration from peak velocity to take-off was particularly indicative of the overall trend demonstrating a CV of 1.97%, a random error of 6.23% and LOA of 0.00 ± 0.002 s. The remaining 17 variables showed high levels of variability (random error >20%), these were mainly related to the duration and slope characteristics of certain key phases (e.g. passive unloading). Discussion: Even though commonly used variables (e.g. power) do not offer advanced mechanical information, they still provide reliable details about CMJ performance. It is clear that more in depth biomechanical information can be gained from multiple levels of analysis; however, the resulting variables do not all display adequate stability for use during consecutive sessions. Whilst it may be worthwhile to conduct a comprehensive analysis of the CMJ to understand how certain interventions bring about changes in performance, the present findings highlight the need to consider a range of reliability statistics before interpreting such findings.

Previous high jump studies have yielded important information regarding successful performance. However, analyses in competitive scenarios have often disregarded athletes' unsuccessful attempts. This study aimed to investigate the biomechanical differences between successful and unsuccessful jumps during competition. High-speed video footage (200 Hz) was obtained from 11 athletes during the 2018 men's World Athletics Indoor Championship Final. From each athlete, one successful (SU) and one unsuccessful (UN) jump at the same bar height were included in the analysis, leaving seven athletes in total. Following whole-body 3D manual digitization, several temporal and kinematic variables were calculated for the run-up, take-off, and flight phases of each jump. During SU jumps, athletes raised the CM to a greater extent (p < 0.01) from take-off. Touchdown in SU jumps was characterized by a faster anteroposterior velocity (p < 0.05), lower backward lean (p < 0.05) and changes in joint angles for the stance and trail limbs (p < 0.05). Athletes also shortened the final contact time during SU jumps (p < 0.01) after producing a longer flight time in the final step of the run-up (p < 0.05). Elite level high jumpers undertake a series of adjustments to successfully clear the bar after UN jumps. These adjustments reinforce the importance of the run-up in setting the foundations for take-off and bar clearance. Furthermore, the findings demonstrate the need for coaches to be mindful of the adjustments required in stance and trail limbs when looking to optimize feedback to athletes during training and competition.

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.

Isokinetic strength assessments are common outcome measures following operatively treated Achilles tendon (AT) ruptures. However, there is a lack of clarity on whether commonly reported outcome measures (such as peak joint moment) are sufficient to describe the extent of long-term functional deficits following AT rupture and repair. The present study conducted a comprehensive isokinetic evaluation of the Triceps surae complex in 12 participants who previously underwent AT rupture and repair. Testing occurred 4.4 (±2.6) years following surgery, and consisted of maximal isokinetic strength assessments of the plantarflexors at two angular velocities (30 and 60 °∙s-1) with the knee in flexed and straight positions. Differences between injured and non-injured limbs were tested through discrete and statistical parametric mapping analysis. Average joint moment showed significant main effects between injured and non-injured limbs, but common isokinetic parameters such as peak moment and angle of peak moment did not. The normalised moment curves showed a significant main effect of limb, angular velocity and knee joint position on joint moment throughout different portions of the range of motion. Temporal analysis revealed a significantly greater ability of the non-injured limb to sustain plantarflexor moments across a range of testing conditions. Participants who had undergone operative treatment of AT ruptures did not display inter-limb differences in discrete isokinetic strength outcomes that are often used in the literature. Instead, temporal analyses were required to highlight the reduced capacity of the injured limb to generate end-range joint moments and to sustain higher levels of joint moment for longer periods.

Hip-shoulder separation (H-Ssep) has been widely researched in many sporting activities (e.g., golf) to provide information on the contribution of torso rotation to performance and injury. Although it is necessary for high jumpers to generate significant long-axis rotation to successfully clear the bar, limited information exists on H-Ssep for high jump athletes. As such, this study aimed to a) characterize the H-Ssep of world-class high jump athletes during competition, b) determine if differences exist between male and female athletes and c) to examine the relationship between H-Ssep and the biomechanical parameters used to describe high jump technique. Twenty-nine world-class high jumpers (17 males, 12 females) were recorded (120-200 Hz) during the 2017 and 2018 World Athletics Championship finals. H-Ssep was quantified at touchdown (TD) and take-off (TO) following manual digitizing (SIMI motion) and a number of other common biomechanical parameters were computed. The observed levels of H-Ssep at TD (−46 ± 12o) and TO (16 ± 11o) were in line with those reported previously for other sports. The magnitude of H-Ssep varied between individuals and showed significant associations with other approach and take-off characteristics. Significant differences in H-Ssep were not evident between male and female athletes despite significant differences in other performance- and technique-related parameters. These findings highlight the divergent take-off characteristics of world-class performers and their reliance on hip-shoulder interactions when generating long axis rotation. Coaches should be mindful of the mechanical and physical consequences of H-Ssep when developing technical models, conditioning interventions and coaching strategies.

Racewalking is an unconventional form of competitive gait that elicits a unique loading profile on lower limb muscles and tendons. This study mapped the structural and mechanical properties of lower limbs in competitive racewalkers and made associations with World Athletics competition performance points. Fourteen international racewalkers (seven men, seven women) were recruited for this study. Static ultrasonography was used to quantify muscle and tendon morphological characteristics. An isokinetic dynamometer was used to measure passive musculotendinous stiffness of the triceps surae, isometric (seven knee/ankle angle combinations) and isokinetic (four angular velocities) strength parameters in the plantarflexors and dorsiflexors, and isokinetic knee flexion and extension strength at five angular velocities. Correlations were found between performance and fascicle length of gastrocnemius medialis (r = –0.569, p = 0.034), dorsiflexor strength at 120°/s (r = 0.649, p = 0.016) and knee flexor strength at 30°/s (r = 0.632, p = 0.020). No associations were found for isometric plantarflexion or passive stiffness properties. Overall, the study showed various morphological and mechanical properties are associated with performance in competitive racewalkers. These associations seem to be related to the specific and unique biomechanical characteristics of racewalking.

Introduction: It is widely believed that ‘strength-type’ (STR) resistance training (RT) is a more effective way of improving maximal strength than ‘hypertrophy-type’ RT (HYP) however, research comparing these training methods is far from unequivocal (Nicholson et al., 2014). Furthermore, cluster training (CL) challenges the traditional way in which strength training sessions are designed although there is a paucity of research into this approach. Our main objective was to compare the adaptations resulting from STR, HYP and CL training over a 6 week period involving the back squat. Methods: 46 trained males (age: 21.8 ± 2.6 years; height: 178.0 ± 6.3cm; mass: 81.1 ± 8.8kg) were matched according to one repetition maximum [1RM] strength before being randomly assigned to one of 4 groups: a) STR: 4x6 reps, 85% 1RM, 900s total rest; b) HYP: 5x10 reps, 70% 1RM, 360s total rest; c) CL-1 4x6 reps, 85% 1RM, 1400s total rest; d) CL-2: 4x6 reps, 90% 1RM, 1400s total rest. Physiological and mechanical variables were measured before, during and after the workouts to investigate the acute training stimulus whilst similar techniques were employed before, during and after a 6 week intervention (2 sessions per week) to investigate the training effects. The findings were analysed using a two-way mixed ANOVA with significance set at p<0.05. Results: From an acute perspective, the STR and HYP workouts resulted in significantly greater reductions in repetition quality than the CL workouts (p<0.05). Furthermore, the STR and HYP workouts showed significant post-exercise elevations in blood lactate concentration (p<0.001). In terms of chronic responses, all four groups elicited significant increases (8-13%; p<0.001) in 1RM strength after training; however, the 1RM improvements were significantly greater for the STR (12.1 ± 2.8%; p<0.05) and CL-2 (13.2 ± 2.2%; p<0.001) groups than the HYP group (8.1 ± 2.5%). Increases in isometric peak force, rate of force development, muscle activity and jump height were not significantly different between groups. Discussion: The STR and CL-2 regimens represented the most favorable means of improving maximal strength. The effectiveness of the STR and CL-2 regimens underlines the importance of longer time under tension and greater impulse generation for strength development but does not support the importance of higher velocities which are often used to signify repetition quality. The findings highlight that CL regimens can offer similar performance enhancements to STR regimens so the decision as to which approach should be use lies with coaches.

It is well established that the inclusion of intra-set rest intervals during cluster-type (CL) resistance exercise enhances both repetition quality and volume-load during training sessions. Although previous CL research has been conducted into different repetition-rest combinations, no study has considered the activity of an individual during intra-set rest intervals. Since it has been shown that the prescription of active inter-set rest intervals during resistance exercise allows a greater number of repetitions (Corder et al., 2000, Journal of Strength & Conditioning Research, 14,151-156), this study examined the impact of active rest on the acute neuromuscular responses to CL resistance exercise. With institutional ethical approval, eight trained males (age: 19.38 ± 1.06 years; height 1.82 ± 0.06m; body mass: 88.1 ± 9.08kg) completed two resistance exercise sessions in a randomised cross-over design separated by at least 48 hours recovery. The passive (PASS) workout involved 3 sets of 8 5s maximal isometric knee extensions with 3 minutes of seated rest between sets and 15s of rest after every 4 repetitions. The active (ACT) workout was identical apart from participants performing active recovery on a stationary ergometer (40W) during all rest intervals. Participants completed three countermovement jumps (CMJ’s) on a force platform (Kistler; 1000 Hz) and three isometric knee extensions (100o knee flexion) attached to a force platform (1000 Hz) pre- and post-workout. A range of kinetic and performance variables were then calculated for the CMJ (e.g. jump height, peak power) and knee extension (peak force [PF], rate of force development) using Bioware software (Version 5.1.3). In addition, root mean square (RMS) activity (1000 Hz) of the knee extensors was recorded (Delsys, USA) before, during and after the workouts as well as the force output of each repetition. A repeated measures ANOVA and subsequent paired t-tests with Bonferroni correction showed a significantly greater (P < 0.01) reduction in PF at post-workout for PASS (-21.25 ± 5.45%) than ACT (-12.39 ± 3.43%). There were also significant reductions (P < 0.01) in PF throughout the PASS workout and a larger post-exercise reduction in RMS activity (45.2%) than that observed for ACT (22.2%). The findings highlight that performance during CL sessions may be further enhanced through the inclusion of active intra-set recovery. Coaches should therefore be mindful that the mode of recovery is an additional consideration when aiming to optimise repetition quality and volume-load during CL resistance exercise.

Purpose: The purpose of this study was to examine the acute and chronic training responses to strength-, hypertrophy- and cluster-type resistance training. Methods: Thirty four trained males were assigned to a strength (STR: 4 x 6 repetitions, 85% of one repetition maximum, [1RM], 900s total rest), hypertrophy (HYP: 5 x 10 repetitions, 70% 1RM, 360s total rest), cluster 1 (CL-1: 4 x 6/1 repetitions, 85% 1RM, 1400s total rest), and cluster 2 (CL-2: 4 x 6/1 repetitions, 90% 1RM, 1400s total rest) regimens which were performed twice weekly for a 6 week period. Measurements were taken before, during and following the four workouts to investigate the acute training stimulus, whilst similar measurements were employed to examine the training effects before and after the intervention. Results: The improvements in 1RM strength were significantly greater for the STR (12.09 ± 2.75%; p<0.05, d=1.106) and CL-2 (13.20 ± 2.18%; p<0.001, d=0.816) regimens than the HYP regimen (8.13 ± 2.54%, d=0.453). In terms of the acute responses, the STR and CL-2 workouts resulted in greater time under tension (TUT) and impulse generation in individual repetitions than the HYP workout (p<0.05). Furthermore, the STR (+3.65 ± 2.54mmol/L-1) and HYP (+6.02 ± 2.97mmol/L-1) workouts resulted in significantly greater elevations in blood lactate concentration (p<0.001) than the CL-1 and CL-2 workouts. Conclusion: CL regimens produced similar strength improvements to STR regimens even when volume-load was elevated (CL-2). The effectiveness of the STR and CL-2 regimens underlines the importance of high loads and impulse generation for strength development.

This study aimed to examine a wide profile of acute biochemical and neuromuscular responses to strength (STR) and hypertrophy (HYP) resistance exercise (RE). Seven trained men completed an STR workout (4 × 6 repetitions, 85% 1 repetition maximum [1RM], 5-minute rest periods), an HYP workout (4 × 10 repetitions, 70% 1RM, 90-second rest periods), and a control condition (CON) in a randomized crossover design. Peak force (PF), rate of force development (RFD), and muscle activity were quantified before and after exercise during an isometric squat protocol. Blood samples were taken 20, 10, and 0 minutes before and 0, 10, and 60 minutes after exercise to measure the concentration of blood lactate (BL), pH, and a number of electrolytes that were corrected for plasma volume changes. No differences were observed between the workouts for changes in PF, RFD, or muscle activity. Repeated contrasts revealed a greater (p ≤ 0.05) increase in BL concentration and reduction in pH after the HYP protocol than the STR or CON conditions. There were similar but significant (p ≤ 0.05) changes in the concentration of a number of electrolytes after both workouts, and a handful of these changes displayed significant correlations with the PF reductions observed after the HYP condition. Although the STR and HYP workouts were significantly different in terms of intensity, volume, and rest, these differences were only observable in the acid-base responses. The present findings reinforce the need for practitioners to look beyond the classification of RE workouts when aiming to elicit specific physiological responses.

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.

INTRODUCTION: Recent research suggests that return-to-play protocols may benefit from the inclusion of angle-specific hamstring:quadriceps (H:Q) ratios to accurately understand muscle balance through the ROM (Lunn et al. 2023). In undertaking angle-specific analyses, most isokinetic knee extension-flexion protocols are conducted using concurrent repetitions (CON) whereby active knee extension is immediately followed by active knee flexion. To reduce the influence of the stretch-shortening cycle and limit axis misalignment, isolated repetitions (ISO) have been recommended (Alt et al. 2014) whereby extension and flexion are completed separately. To inform athlete screening protocols, this study examined the effect of CON and ISO protocols on discrete and angle-specific hamstring:quadriceps ratios. METHODS: Fifteen healthy males (age: 27 ± 4 years; height: 184 ± 9 cm; body mass: 80 ± 9 kg) performed isokinetic tests of the knee flexors and extensors (60 deg/s) using CON and ISO repetitions while sagittal-plane kinematics were captured (100 Hz) to quantify axis misalignment. Statistical parametric mapping then enabled the effects of protocol type (CON vs. ISO) and axis misalignment (uncorrected vs. corrected data) to be compared. RESULTS: The use of uncorrected data resulted in an underestimation of discrete conventional (−10.2%, p < 0.001) and functional (−9.2%, p < 0.05) H:Q ratios with these differences being observed for all angle-specific ratios (p < 0.001). The use of concurrent repetitions resulted in a significant overestimation of the H:Q ratio (+7.4%, p < 0.05) with the differences being most prevalent at extended knee joint positions. Despite the main effect(s) of protocol type and axis misalignment, no significant interactions were observed. CONCLUSION: Practitioners should be mindful that the use of concurrent repetitions will result in a significantly higher conventional H:Q ratio which will particularly influence angle-specific ratios in more extended knee joint positions. This may increase the likelihood of “false negative” injury risk categorisation during “time-efficient” protocols involving concurrent repetitions. Whilst the use of corrected knee moment data is preferable, practitioners should be mindful that the use of isolated repetitions and corrected joint moment data does not lead to significant differences in discrete or angle-specific H:Q ratios when compared with uncorrected data obtained from concurrent repetitions.

Most measurements of isokinetic hamstring:quadriceps (H:Q) strength ratios are conducted using concurrent repetitions, whereby active knee extension is immediately followed by active knee flexion. To reduce the influence of the stretch-shortening cycle and limit axis misalignment, isolated repetitions have been recommended, whereby extension and flexion are completed separately. To inform screening protocols, this study examined the effect of concurrent and isolated trials on discrete and angle-specific H:Q ratios. Fifteen males (age: 27 ± 4 years; height: 184 ± 9 cm; body mass: 80 ± 9 kg) performed isokinetic tests of the knee flexors and extensors (60 °/s) using concurrent and isolated trials while sagittal kinematics were captured (100 Hz). Statistical parametric mapping enabled the effects of protocol type (concurrent vs. isolated) and axis misalignment (uncorrected vs. corrected) to be compared. Uncorrected data resulted in an underestimation of discrete conventional (−10.17%, p < 0.001) and functional (−9.21%, p < 0.05) ratios with differences being observed for all angle-specific ratios (p < 0.001). The use of concurrent repetitions resulted in a significant overestimation of the conventional H:Q ratio (+7.41%, p < 0.05) with the differences being most prevalent at more extended (24 - 45° knee flexion, p < 0.05) knee joint positions. Dynamometer users should be aware that concurrent repetitions increase the likelihood of “false negative” injury risk categorisation. Nevertheless, the common practice of using uncorrected data from concurrent repetitions does not lead to significant differences in discrete or angle-specific H:Q ratios when compared with corrected data obtained from isolated repetitions.

INTRODUCTION: Muscle-tendon interaction during movement can be categorised into energy conservation or power amplification/attenuation strategies (1), and the mechanical and morphological properties of male athletes’ tendons adapt to these loading demands (2). Although previous research observed no differences in tendon properties between female endurance runners and inactive controls (3, 4), little is known about these properties in females undergoing habitual power amplification-type loading, such as that experienced by team sport athletes. Therefore, this study investigated Achilles’ tendon (AT) properties in trained female endurance runners and netballers. METHODS: An observational investigation of 7 national level female netballers (16.2 ± 4.5 years netball training experience) and 7 female runners (8.3 ± 2.9 years training) was conducted. AT thickness was assessed at rest using B-mode ultrasound. The AT moment arm was calculated using the tendon excursion method. Participants performed graded isometric ankle plantar flexion contractions on a Cybex dynamometer until a voluntary maximum was reached, whilst dynamic ultrasound recorded displacement of the gastrocnemius medialis myotendinous junction. From each contraction plantar flexion moment, AT force, elongation, and strain were calculated. AT stiffness was defined as the slope of the AT force-elongation relationship (from 20-100% of maximum force). Mean differences (MD) with 95% confidence intervals (CI), Student’s t-tests, and Hedge’s g effect sizes (ES) were used to assess differences in AT properties between groups. RESULTS: Netballers displayed a significantly greater maximal plantar flexion moment (MD 58.1 N.m-1, CI 35.5-80.7 N.m-1, ES 2.81, p<0.001), AT force (MD 822.4 N, CI 294.4-1350.5 N, ES 1.70, p=0.008), AT elongation (MD 5.70 mm, CI 0.40-11.07 mm, ES 1.17, p=0.044), and AT thickness (MD 0.69 mm, CI 0.08-1.30 mm, ES 1.24, p=0.031). No significant differences were found in maximal strain, stiffness, length, or moment arm. CONCLUSION: The greater AT thickness of the netball group suggests that the power amplification-type loading demands inherent to netball training (i.e., jumping, landing) have a hypertrophic effect on the tendon. Additionally, the greater maximal plantar flexion moment, and hence AT force experienced by the netballers may also contribute to this hypertrophic stimulus. This adaptation may be protective in nature, as increased thickness (and presumably cross-sectional area) would reduce peak operating stress and enhance the safety factor of the tendon. Despite differences in AT thickness, no differences in strain or stiffness were found, corroborating earlier findings of uncoupled mechanical and morphological properties (2). These results provide evidence that the AT can adapt to high intensity loading in females. 1. Roberts and Azizi, J Exp Bio, 2011 2. Wiesinger et al., PLOS One, 2016 3. Magnusson et al., Int J Exp Path, 2007 4. Westh et al., Scand J Med Sci Sport 2008

Introduction Conventional and functional knee strength ratios, defined using peak joint moment of the flexors and extensors, are used in practice to estimate injury risk (Baroni et al., 2020). Despite literature commonly reporting these values there remains uncertainty regarding their functional value (Kellis et al., 2022). It has been suggested that using a time-series metric from angle-specific joint moments might be more successful at identifying injury risk (Read et al., 2022). Therefore, the aim of this study was to compare discrete strength ratios commonly used in practice with angle-specific ratios to determine differences between the two measures. Method Twenty-eight footballers were recruited from the same English Premier League club (age: 22±4 y; stature: 1.81±0.07 m; body mass: 75.2±6.8 kg). Isokinetic testing was conducted for the knee flexors and extensors in a concentric motion at two angular velocities (60°/s and 240°/s) and in an eccentric motion (for the knee flexors only) at one angular velocity (30°/s) using an isokinetic dynamometer (Biodex Medical Systems). Conventional, discrete H:Q ratio’s (cHQR-D) were calculated as the ratio between peak joint moment in the flexors and extensors at 60°/s. Functional, discrete H:Q ratio’s (fHQR-D) were calculated as the peak joint moment in the flexors during the eccentric condition (30o/s) and the extensors at 240°/s. Angle-specific ratios (cHQR-AS and fHQR-AS) were computed as the ratio between flexor and extensor joint moments for all angles where both muscle groups were in the isokinetic range. Mean absolute residuals were then computed to compare between discrete and angle specific ratios. Results Peak joint moment for flexors and extensors at 60°/s was 129.4±21.6 and 240.9±35.6 Nm, respectively (cHQR-D = 0.54±0.07). Eccentric peak joint moment for the flexors was 165.9±34.6 Nm, and concentric peak moment for the extensors at 240°/s was 145.3±18.4 Nm (fHQR-D = 1.15±0.21). Throughout the isokinetic range, average cHQR-AS ranged from 0.41-0.98 with a mean absolute residual of 0.11±0.11 versus cHQR-D. In comparison, the average fHQR-AS ranged from 0.98-1.33 with a larger mean absolute residual of 0.26±0.14 versus fHQR-D. Conclusion Neither conventional nor functional discrete ratios were fully representative of angle-specific ratios throughout the isokinetic range. However, the average residual for the conventional ratio was lower than the functional ratio, despite a greater range of values for cHQR-AS. Suggesting that discrete conventional ratios are more representative of angle-specific ratios over a greater range of joint angles, compared to discrete functional ratios. Furthermore, discrete functional ratios are not representative of angle specific functional ratios, which could mask athletes who may have fHQR deficits and may be at risk of injury. References Baroni, BM et al. (2020). J Strength Cond Res, 34, 281-293. Kellis, E et al. (2022). J Sport Health Sci. Read, PJ et al. (2022). J Sports Sci, 1-7.

Training for both sporting and military performance is common practice within army trainee populations, although it is currently unknown what effect this combination of training methods may have on the physical attributes required for overall physical preparedness. This study examined the effects of sport-specific training on general fitness in a professional military population. Four hundred and twenty-three Greek male army cadets completed a 12-week training regimen involving standard physical training (callisthenics, strength and endurance running exercises) and either general military training (GMT) or sport military training (SMT). A series of physical tests took place before and after the training period: a mile run, pull-ups, 50 m swim and an obstacle course run. Both the GMT and SMT groups showed significant (p < 0.001) improvements in all physical tests. However, the SMT group produced significantly greater improvements in all four tests (pull-ups [p < 0.001], 50 m swim [p < 0.05], obstacle course [p < 0.01] and mile run [p < 0.01]) compared to the GMT group. Furthermore, different types of SMT (e.g. rock climbing and track sprinting) achieved greater improvements (p < 0.001–0.01) in certain physical tests when compared to other forms of SMT (e.g. Pankration, Fencing). These results indicate that cadets undertaking concurrent participation in general and sport military training are overall better prepared for physical performance than their counterparts who undertake only general military training. Military conditioning per sonnel should be aware of the positive interplay between general and sports specific training in forming a preparation strategy designed for physical performance.

There has been increasing interest in new measurement systems that provide instantaneous spatiotemporal data whilst being less expensive and more accessible to practitioners. The aim of this study was to examine the agreement between the OptoJump Next system (OJ), videography and force platform methods for measuring spatiotemporal variables during the acceleration phase of sprinting. Ninety-nine university students completed two maximal 20 metre sprints in which spatiotemporal parameters (contact time [CT], flight time [FT], step length [SL] and step rate) were simultaneously obtained using the OJ system (1000 Hz), videography (200 Hz), and force platforms (1000 Hz). The OJ and video systems showed high agreement for the measurement of step length (bias: 0.003-0.007 m, random error [RE]: 0.057-0.071 m). For temporal parameters, OJ tended to overestimate CT compared to the force platforms (bias: 0.012-0.014 s, RE: 0.009-0.021 s) and also underestimated FT (bias: 0.012-0.013 s, RE: 0.011-0.012 s). Despite the lower sampling rate, videography showed a closer agreement with the force platform for both CT (bias: 0.005-0.010 s, RE: 0.009-0.021 s) and FT (bias: 0.005-0.007 s, RE: 0.008-0.010 s). Although OptoJump next provides instantaneous spatiotemporal parameters, coaches may wish to adjust for the systematic overestimation of CT (0.013 s) and underestimation of FT (0.012 s) in order to obtain sprint spatiotemporal data that aligns to force platforms.

We mapped structural and functional characteristics of muscle‐tendon units in a population exposed to very long‐term routine overloading. Twenty‐eight military academy cadets (age = 21.00 ± 1.1 years; height = 176.1 ± 4.8 cm; mass = 73.8 ± 7.0 kg) exposed for over 24 months to repetitive overloading were profiled via ultrasonography with a senior subgroup of them (n = 11; age = 21.4 ± 1.0 years; height = 176.5 ± 4.8 cm; mass = 71.4 ± 6.6 kg) also tested while walking and marching on a treadmill. A group of eleven ethnicity‐ and age‐matched civilians (age = 21.6 ± 0.7 years; height = 176.8 ± 4.3 cm; mass = 74.6 ± 5.6 kg) was also profiled and tested. Cadets and civilians exhibited similar morphology (muscle and tendon thickness and cross‐sectional area, pennation angle, fascicle length) in 26 out of 29 sites including the Achilles tendon. However, patellar tendon thickness along the entire tendon was greater (P < .05) by a mean of 16% for the senior cadets compared with civilians. Dynamically, cadets showed significantly smaller ranges of fascicle length change and lower shortening velocity in medial gastrocnemius during walking (44.0% and 47.6%, P < .05‐.01) and marching (27.5% and 34.3%, P < .05‐.01) than civilians. Furthermore, cadets showed lower normalized soleus electrical activity during walking (22.7%, P < .05) and marching (27.0%, P < .05). Therefore, 24‐36 months of continuous overloading, primarily occurring under aerobic conditions, leads to more efficient neural and mechanical behavior in the triceps surae complex, without any major macroscopic alterations in key anatomical structures.

This report provides an analysis of all finalists’ best jumps and comprised a biomechanical analysis of the two steps before the take-off board along with the hop, step and jump sections also being presented. Finally, an analysis of the landing is also presented. This is a useful analysis for those interested in triple jump performance. The full report is available from the IAAF website: https://www.iaaf.org/about-iaaf/documents/research

This report provides a biomechanical analysis of the best performances of all women's long jump finalists of the three steps before take-off, with a more in-depth examination of the last step. This is a useful tool for those interested in the approach to to the take-off board. The full report is available from the IAAF website: https://www.iaaf.org/about-iaaf/documents/research

This report provides an analysis of all finalists’ best jumps and comprised a biomechanical analysis of the two steps before the take-off board along with the hop, step and jump sections also being presented. Finally, an analysis of the landing is also presented. This is a useful analysis for those interested in triple jump performance. The full report is available from the IAAF website: https://www.iaaf.org/about-iaaf/documents/research

This report provides a biomechanical analysis of the best performances of all men's long jump finalists of the three steps before take-off, with a more in-depth examination of the last step. This is a useful tool for those interested in the approach to to the take-off board. The full report is available from the IAAF website: https://www.iaaf.org/about-iaaf/documents/research

INTRODUCTION Research within Rugby league (RL) tackle investigations using video analysis has often used two sources of variables. The exception being King et al (2010) who described the characteristics of the RL tackle event such as number of tacklers and tackle height of the first tackler. However, the majority of investigations have either adopted technical variables from rugby union (RU) tackle variables (Sperenza et al., 2017) or technical criteria from coaching cues (Gabbett, 2008). In doing so, content validity and relevance to RL could be questioned (O’Donoghue, 2014). The aim of this study was to adopt a 5 stage process to determine tackle variables which are valid and reliable for RL research METHODS A 5 stage process was undertaken based upon recommendations by O’Donoghue (2014). STAGE 1 involved a synthesis of literature and examined phases of the tackle, variables describing the tackle descriptions of these variables research. A draft variable list was then developed before the start of STAGE 2. To achieve content validity and relevancy, STAGE 2 formed an expert group of practitioners to critique the previously formed draft variable list and develop new phases, variables and descriptors. STAGE 3 refined the variable list based upon the practitioner consultation. STAGE 4 established an expert group agreement in the refined variable list. Finally, STAGE 5 tested intra and inter-reliability of the list using Kappa statistics (McHugh, 2012). RESULTS The agreed variable list comprised of 6 phases including defensive start point, pre-contact, initial contact, post-contact and play the ball phases. Within the phases 66 variables were determined. The intra- and inter-reliability testing resulted in at least moderate agreement (>0.7) (McHugh, 2012) of all phases. DISCUSSION Due to possessing both strong relevance to an RL tackle and demonstrating good levels of reliability, researchers can be confident that the variables within the list are valid for research purposes (O’Donoghue, 2014). In addition, the rigorous 5 stage process of validating the content of the variable list should be used when determining different variables within different sports and actions for research purposes. In doing so, researchers can be confident that they are valid in use and thus can be used consistently for research purposes. Furthermore, the findings show that although there are similarities between a RU and RL tackle, clear differences exist and therefore justifies the need for specific RL variables during tackle research.

Research findings indicate that the inter-set rest interval is an important variable when prescribing resistance training (RT) programmes however, there is a growing focus of attention on the additional use of short intra-set rest intervals in the approach known as cluster set (CS) training. Despite evidence that supports the positive effects of CS configurations on the acute and chronic responses to RT, numerous challenges exist for practitioners when aiming to utilise this training concept. As such, this review aims to identify these challenges and offer recommendations in light of the contemporary research into this concept. The Discover, PubMed, Sport Discus, Research Gate and Google Scholar databases were searched in order to locate previous peer reviewed investigations which examined the acute and/or chronic responses to manipulating intra-set rest intervals. Twenty-five studies were reviewed after the inclusion criteria had been applied. Although the review highlighted that CS configurations may offer superior alternatives to traditional set configurations when seeking to emphasise specific acute or chronic responses, contrasting findings exist with regards to the chronic effects of CS configuration on various physical attributes (e.g. strength, power, hypertrophy) which presents challenges for practitioners when interpreting the literature. The contrasting findings result from a number of key methodological differences (e.g. intra-set rest duration) which practitioners need to be aware of when designing CS configurations. In terms of practical considerations, CS configurations may present challenges due to their time-consuming and monotonous nature but offer advantages in terms of reducing perceived exertion, cardiovascular demands, enhancing the performance and technique of key explosive exercises.

Muscle-tendon unit (MTU) assessments can be categorised into local (e.g. tendon strain) or global (e.g. jump height) assessments. Although menstrual cycle phase may be a key consideration when implementing these assessments in female athletes, the reliability of many MTU assessments is not well defined within female populations. Therefore, the purpose of this study was to report the test-retest reliability of local and global MTU assessments during the early follicular phase of the menstrual cycle. Seventeen naturally menstruating females (age 28.5 ± 7.3 years) completed local and global MTU assessments during two testing sessions separated over 24-72 hours. Local tests included Achilles’ tendon mechanical testing and isometric strength of ankle plantar flexors and knee extensors, whereas global tests included countermovement, squat, and drop jumps, and the isometric midthigh pull. Based on intraclass correlation coefficient (ICC) statistics, poor to excellent reliability was found for local measures (ICC: 0.096-0.936). Good to excellent reliability was found for all global measures (ICC: 0.788-0.985), excluding the eccentric utilisation ratio (ICC 0.738) and most rate of force development metrics (ICC: 0.635-0.912). Isometric midthigh pull peak force displayed excellent reliability (ICC: 0.966), whereas force-time metrics ranged from moderate to excellent (ICC: 0.635-0.970). Excluding rate of force development (coefficient of variation [CV]: 10.6-35.9%), global measures (CV: 1.6-12.9%) were more reproducible than local measures (CV: 3.6-64.5%). However, local metrics directly measure specific properties of the MTU, and therefore provide valuable information despite lower reproducibility. The novel data reported here provides insight into the natural variability of MTU assessments within female athletes, which can be used to enhance the interpretation of other female athlete data, especially that which aims to investigate other aspects of variability, such as the menstrual cycle.

Muscle-tendon unit (MTU) assessments can be categorised into local (e.g., tendon strain) or global (e.g., jump height) assessments. Although menstrual cycle phase may be a key consideration when implementing these assessments in female athletes, the reliability of many MTU assessments is not well defined within female populations. Therefore, the purpose of this study was to report the test-retest reliability of local and global MTU assessments during the early follicular phase of the menstrual cycle. Seventeen naturally menstruating females (age 28.5 ± 7.3 years) completed local and global MTU assessments during two testing sessions separated over 24–72 hours. Local tests included Achilles’ tendon mechanical testing and isometric strength of ankle plantar flexors and knee extensors, whereas global tests included countermovement, squat, and drop jumps, and the isometric midthigh pull. Based on intraclass correlation coefficient (ICC) statistics, poor to excellent reliability was found for local measures (ICC: 0.096–0.936). Good to excellent reliability was found for all global measures (ICC: 0.788–0.985), excluding the eccentric utilisation ratio (ICC 0.738) and most rate of force development metrics (ICC: 0.635–0.912). Isometric midthigh pull peak force displayed excellent reliability (ICC: 0.966), whereas force-time metrics ranged from moderate to excellent (ICC: 0.635–0.970). Excluding rate of force development (coefficient of variation [CV]: 10.6–35.9%), global measures (CV: 1.6–12.9%) were more reproducible than local measures (CV: 3.6–64.5%). However, local metrics directly measure specific properties of the MTU, and therefore provide valuable information despite lower reproducibility. The novel data reported here provides insight into the natural variability of MTU assessments within female athletes which can be used to enhance the interpretation of other female athlete data, especially that which aims to investigate other aspects of variability, such as the menstrual cycle.

This study tested the performance of OpenPose on footage collected by two cameras at 200 Hz from a real-life competitive setting by comparing it with manually analyzed data in SIMI motion. The same take-off recording from the men's Long Jump finals at the 2017 World Athletics Championships was used for both approaches (markerless and manual) to reconstruct the 3D coordinates from each of the camera's 2D coordinates. Joint angle and Centre of Mass (COM) variables during the final step and take-off phase of the jump were determined. Coefficients of Multiple Determinations (CMD) for joint angle waveforms showed large variation between athletes with the knee angle values typically being higher (take-off leg: 0.727 ± 0.242; swing leg: 0.729 ± 0.190) than those for hip (take-off leg: 0.388 ± 0.193; swing leg: 0.370 ± 0.227) and ankle angle (take-off leg: 0.247 ± 0.172; swing leg: 0.155 ± 0.228). COM data also showed considerable variation between athletes and parameters, with position (0.600 ± 0.322) and projection angle (0.658 ± 0.273) waveforms generally showing better agreement than COM velocity (0.217 ± 0.241). Agreement for discrete data was generally poor with high random error for joint kinematics and COM parameters at take-off and an average ICC across variables of 0.17. The poor agreement statistics and a range of unrealistic values returned by the pose estimation underline that OpenPose is not suitable for in-competition performance analysis in events such as the long jump, something that manual analysis still achieves with high levels of accuracy and reliability.

Introduction: Hypertrophy-type (HYP) resistance exercise (RE) is typically designed to elicit changes in fibre size whereas strength-type (STR) RE is usually employed to improve strength via mainly neural adaptations. Although previous studies have investigated the acute responses to different RE workouts (McCaulley et al., 2009), the mechanisms responsible for different long-term adaptations are still widely debated. Thus, this study examined the acute neuromuscular responses to STR and HYP workouts which utilised the back squat exercise. Methods: Seven trained males (23.6 ± 2.7 years) completed a STR workout (4x6 repetitions at 85%1RM, 5 min rest intervals), a HYP workout (4x10 repetitions at 70%1RM, 90s rest intervals) and a control condition (CON) in a randomised cross-over design separated by at least 48 hours. Subjects performed 3×4s maximal isometric back squats (100o knee flexion), by using a modified squat rack attached to a Kistler force platform (1000 Hz), immediately pre- and post- each workout. Several kinetic performance variables were determined and investigated statistically by using a two-factor within subjects ANOVA. Results: Repeated contrast tests showed a greater reduction in Peak Isometric Force following the HYP (-18.06%) than CON condition (-1.21%) (p=0.017). Also the HYP workout resulted in greater reductions in the rate of force development (RFD) during the initial 0.05s (-21%, p=0.023) and 0.1s (-29%, p=0.047) of the force-time curve as well as greater increases in the time required to produce 500N (92%, p=0.018) when compared with the CON condition. The STR workout was characterised by a greater reduction in RFD during the initial 0.2s of the force-time curve (-0.19%, p=0.034) as well as greater increases in the time required to produce 250N (28%, p=0.025) when compared to the CON condition. No significant differences were observed between the STR and HYP conditions for any variable. Discussion: Both workouts resulted in acute neuromuscular fatigue possibly via different pathways. The acute reductions in RFD following the STR workout may have resulted from central fatigue whereas the reductions in RFD and PF following the HYP workout may be indicative of central and peripheral fatigue (Hakkinen et al., 1994; McCaulley et al., 2009). Although STR and HYP workouts are typically prescribed in order to emphasise different long-term adaptations, marked differences in the acute neuromuscular responses were not observed. Such findings may question the prescription of future similar workouts when aiming to elicit distinctly different neuromuscular stimuli.

Introduction: Information on the acute metabolic responses to resistance exercise (RE) may provide valuable information regarding peripheral fatigue factors. However, most studies have examined a relatively narrow range of metabolic responses to different RE workouts. In addition, much of the research has not accounted for plasma volume (PV) changes. This study compared a wider profile of metabolic responses following strength (STR) and hypertrophy-type (HYP) back squat workouts, when corrected for PV changes. Methods: Following one repetition maximum (1RM) testing, seven trained males (23.6±2.7 years) completed a STR workout (4x6 repetitions, 85% 1RM, 5 min rest intervals), a HYP workout (4x10 repetitions, 70% 1RM, 1.5 min rest intervals) and a control condition (CON) in a randomised cross-over design separated by at least 48 hours. Capillary blood samples were taken pre- (-20min,-10min,-0min) and post-exercise (+0min,+10min,+60min) in order to measure concentration of blood lactate (BL), electrolytes, haemoglobin (Hb) and haematocrit (Hct). The samples were analysed using a blood gas CO-Oximeter and electrolyte analyser (GEM Premier 4000). Following calculation of PV changes from Hb and Hct, variables were corrected using the method of Kraemer & Brown (1986). A two-factor within subjects ANOVA was employed for statistical analysis. Results: Average PV changes were -8.05 ± (11.45%), -8.02 ± (6.54%) and -3.32 ± (6.97%) for the STR, HYP and CON conditions respectively. Repeated contrast tests revealed a significantly (p<0.05) greater increase (at +0min) in BL concentration following the HYP condition (0.83 ± 0.13 mmol/L-1 to 9.67 ± 2.45 mmol/L-1) than the STR (1.07 ± 0.38 mmol/L-1 to 6.66 ± 2.31 mmol/L-1) or CON (0.97 ± 0.48 mmol/L-1 to 1.15 ± 0.55 mmol/L-1) conditions, this was also evident at +10min. In addition, the HYP workout resulted in significantly greater (p<0.05) reductions in chloride, sodium and potassium than the CON condition whilst the STR workout also resulted in significantly greater reductions in chloride, sodium and calcium than the CON condition. Discussion: PV changes were similar to those reported previously following RE (Wallace et al., 1990). In addition, the HYP workout had a notable impact on metabolite accumulation as evidenced by significant changes in the concentration of BL and a number of electrolytes. Greater metabolic stress has been previously reported following HYP than STR workouts (McCaulley et al., 2009). However, the data highlight the need to consider a wider profile of metabolic variables when examining the acute responses to HYP workouts.

Rugby league (RL) carries a high injury incidence with 61% of injuries occurring at tackles. The ball carrier has a higher injury incidence than the defender, therefore understanding mechanisms occurring during injurious tackles are important. Given the dynamic, open nature of tackling, characteristics influencing tackle outcome likely encompass complex networks of dependencies. This study aims to identify important classifying characteristics of the tackle related to ball carrier injurious and non-injurious events in RL and identify the characteristics capability to correctly classify those events. Forty-one ball carrier injuries were identified and 205 matched non-injurious tackles were identified as controls. Each case and control were analysed retrospectively through video analysis. Random forest models were built to 1.) filter tackle characteristics possessing relative importance for classifying tackles resulting in injurious/non-injurious outcomes and 2.) determine sensitivity and specificity of tackle characteristics to classify injurious and non-injurious events. Six characteristics were identified to possess relative importance to classify injurious tackles. This included ‘tackler twisted ball carrier’s legs when legs were planted on ground’, ‘the tackler and ball carrier collide heads’, ‘the tackler used body weight to tackle ball carrier, ‘the tackler has obvious control of the ball carrier’ ‘the tackler was approaching tackle sub-maximally’ and ‘tackler's arms were below shoulder level, elbows were flexed’. The study identified tackle characteristics that can be modified in attempt to reduce injury. Additional injury data are needed to establish relationship networks of characteristics and analyse specific injuries. Sensitivity and specificity results of the random forest were 0.995 and 0.525.

We do not yet understand the concurrent validity of markerless motion capture (MMC) to measure kinematic differences between multiple gait speeds. This study determined the capacity of Theia3D (Theia Markerless Inc.) MMC to detect sagittal-plane kinematic responses to different gait speeds during walking (3 and 5 km/h) and running (10 and 12 km/h). Fourteen participants ambulated on a motorised treadmill, while markerbased motion capture, through optoelectronic cameras (Oqus 7+, Qualisys AB), and MMC, through videos (Miqus, Qualisys AB) were synchronously collected. Sagittal plane changes in pelvis, hip, knee, and ankle kinematics were compared. Mostly excellent waveform similarity was found for joint kinematic changes (coefficient of multiple determination [CMD] ≥ 0.87), but pelvic tilt was less similar (CMD ≤ 0.48). Agreement between outcome measures (joint minima and maxima, range of motion) was mostly good-to-excellent (intraclass correlation coefficient [ICC] = 0.475-0.950) with standard error of measurement values of less than 1°. Pelvis kinematics showed lower agreement between systems (ICC = 0.032-0.776). In this study, Theia3D detected changes in hip, knee, and ankle sagittal-plane joint kinematics between speeds with a similar accuracy to the marker-based approach. Therefore, Theia3D is appropriate for use if interested in lower-limb sagittal joint kinematics, but not pelvic tilt.

The aims of this study were: (1) to quantify interlimb asymmetries in EPL soccer players in the context of kicking limb preference and (2) to establish the relationship between interlimb asymmetries and measures of physical performance. Twenty-two players (age: 21.8 ± 4.4 years) from an EPL club performed a running gait assessment (20 km/h) and unilateral countermovement jumps, a CoD assessment (modified 505 test), and an isokinetic knee extension/flexion protocol using each leg. Asymmetries were quantified using the percentage difference method and Pearson’s correlations were used to quantify the association between variables. Players displayed the greatest level of asymmetry in isokinetic strength measures (5.9-12.7%) and lower levels of asymmetry in gait (1.6-7.7%), jump (0.9-7.0%) and CoD (1.9-3.5%) assessments. The influence of the preferred kicking limb was most evident in the isokinetic assessment with the players showing dominance in the preferred limb for knee flexor strength and in the non-preferred limb for knee extensor strength. These manifested in the asymmetry values calculated for the hamstring:quadricep (H:Q) ratios at 60°/s (8.80 ± 7.82%) and 240°/s (11.22 ± 7.04%) and in the functional H:Q ratio (12.67 ± 8.25%). The asymmetry values for peak extensor moment at 240°/s showed a significant correlation (ρ = ─0.55, p = 0.034) with 10 m time in the CoD assessment. These findings provide benchmark asymmetry data for soccer practitioners and reveal that kicking limb preferences may bring about interlimb differences in the H:Q ratio which raises important considerations in the design of testing batteries and injury reduction interventions.

Bissas, A, Paradisis, GP, Nicholson, G, Walker, J, Hanley, B, Havenetidis, K, and Cooke, CB. Development and maintenance of sprint training adaptations: an uphill-downhill study. J Strength Cond Res XX(X): 000-000, 2020-We examined the development of performance adaptations resulting from an uphill-downhill training program and monitored the decline of adaptations during detraining. Twenty-eight men were randomly assigned to 1 of 2 sprint training groups who trained 3 times per week for 6 weeks and a control group (C). The uphill-downhill group (U+D) trained on an 80-m platform with 3° slopes, whereas the horizontal (H) group trained on flat track. Subjects were tested for maximal running speed (MRS), associated kinematics, and leg strength before and after training, with U+D subjects also tested after weeks 2 and 4 of training, and after a 3-week detraining period. The U+D group increased their MRS by 3.7% (from 8.75 ± 0.72 to 9.07 ± 0.64 m·s, p < 0.05), their stride rate by 3.1% (from 4.21 ± 0.21 to 4.34 ± 0.18 Hz, p < 0.05), and their knee extensors' maximum isometric force by 21% (from 2,242 ± 489 to 2,712 ± 498 N, p < 0.05) after training. The time course of changes showed declines for weeks 1-4 (1.4-5.1%), but an ascending trend of improvement compensated all losses by the end of week 6 (p < 0.05). During detraining, no decreases occurred. No changes were observed for the H and C groups. The minimum period to produce positive effects was 6 weeks, with a very good standard of performance maintained 3 weeks after training. U+D training will prove useful for all athletes requiring fast adaptations, and it can fit into training mesocycles because of its low time demands.

The purpose of this study was to determine the importance of physical qualities for speed and change of direction (CoD) ability in female soccer players. Data were collected on 10 female soccer players who were part of a professional English Women’s Super League team. Player assessments included anthropometric (stature and body mass), body composition (dual-energy X-ray absorptiometry), speed (10m, 30m sprint), CoD ability (505 agility), aerobic (Yo-Yo Intermittent Recovery Test), lower-body strength (bilateral knee extensions) and power (countermovement jump [CMJ], squat jump [SJ], 30cm drop jump [DJ]) measures). The relationships between the variables were evaluated using eigenvector analysis and Pearson correlation analysis. Multiple linear regression revealed that the performance variables (10 and 20m speed, mean 505, and CoD deficit mean) can be predicted with almost 100% accuracy (i.e. adjusted R2 > 0.999) using various combinations of the predictor variables (DJ height, CMJ height, SJ height, lean body mass). An increase of one standard deviation (SD) in DJ height was associated with reductions of -5.636 and 9.082 SD in 10 m and 20 m sprint times. A one SD increase in CMJ also results in a reduction of -3.317 and -0.922 SD respectively in mean 505 and CoD deficit mean values. This study provides comparative data for professional English female soccer players that can be used by strength and conditioning coaches when monitoring player development and assessing the effectiveness of training programmes. Findings highlight the importance of developing reactive strength to improve speed and CoD ability in female soccer players.

Introduction Research within Rugby league (RL) tackle investigations using video analysis has often used two sources of variables. The exception being King et al (2010) who described the characteristics of the RL tackle event such as number of tacklers and tackle height of the first tackler. However, the majority of investigations have either adopted technical variables from rugby union (RU) tackle variables (Sperenza et al., 2017) or technical criteria from coaching cues (Gabbett, 2008). In doing so, content validity and relevance to RL could be questioned (O’Donoghue, 2014). The aim of this study was to adopt a 5 stage process to determine tackle variables which are valid and reliable for RL research. Method A 5 stage process was undertaken based upon recommendations by O’Donoghue (2014). STAGE 1 involved a synthesis of literature and examined phases of the tackle, variables describing the tackle descriptions of these variables research. A draft variable list was then developed before the start of STAGE 2. To achieve content validity and relevancy, STAGE 2 formed an expert group of practitioners to critique the previously formed draft variable list and develop new phases, variables and descriptors. STAGE 3 refined the variable list based upon the practitioner consultation. STAGE 4 established an expert group agreement in the refined variable list. Finally, STAGE 5 tested intra and inter-reliability of the list using Kappa statistics (McHugh, 2012). Results The agreed variable list comprised of 6 phases including defensive start point, pre-contact, initial contact, post-contact and play the ball phases. Within the phases 66 variables were determined. The intra- and inter-reliability testing resulted in at least moderate agreement (>0.7) (McHugh, 2012) of all phases. Discussion Due to possessing both strong relevance to an RL tackle and demonstrating good levels of reliability, researchers can be confident that the variables within the list are valid for research purposes (O’Donoghue, 2014). In addition, the rigorous 5 stage process of validating the content of the variable list should be used when determining different variables within different sports and actions for research purposes. In doing so, researchers can be confident that they are valid in use and thus can be used consistently for research purposes. Furthermore, the findings show that although there are similarities between a RU and RL tackle, clear differences exist and therefore justifies the need for specific RL variables during tackle research.

Objective To (1) systematically review the literature to identify which match-related risk factors and mechanisms of rugby tackle events result in musculoskeletal injury; concussion; head injury assessments; and head impacts or head accelerations; and (2) identify the perceived importance and feasibility of potential intervention strategies for tackle-related injury reduction in the rugby codes. Design A systematic search was performed using PRISMA guidelines. Risk factors/mechanisms associated with tackle injuries across the rugby codes were extracted. After extraction, 50 international rugby experts participated in a Delphi poll. Via content analysis, expert-recommended risk factors/mechanisms were developed. In round two, experts rated all risk factors and mechanisms for importance to injury risk. In round three, the feasibility of law changes, coach and player education and training as interventions to reduce injury risk for each injury risk factor/mechanism deemed important during round two were rated. Data sources PubMed [MEDLINE], Scopus, SPORTDiscus [EBSCOhost] and CINAHL. Eligibility criteria Eligible studies included cohort, observational and cross-sectional designs, that included male or female rugby union, league, or sevens players. Results Thirty-seven eligible studies were identified, with 138 injury risk factors/mechanisms extracted. 70% of the studies were rated ‘high quality’, with 30% moderate quality. Thirty-eight new risk factors/mechanisms were recommended by the expert group, eight being identified as important and highly feasible for modification by an intervention strategy. ‘The tackler placing their head on the incorrect side of the ball carrier’ was described as the most important mechanism, with ‘training’ and ‘coach/player education’ thought to be highly feasible interventions. Conclusion Numerous risk factors or mechanisms associated with tackle-related injury appear important and modifiable, helping to guide interventions to reduce injury risk in the rugby tackle.

Abstract

Abstract

Measurements of muscle-tendon unit (MTU) function can be categorised into local (e.g. tendon strain) or global (e.g. jump height) assessments. Although menstrual cycle phase may be a key consideration when implementing these assessments in female athletes, the reliability of many MTU assessments is not well defined within female populations. Therefore, the purpose of this study was to report the test-retest reliability of local and global MTU function assessments during the early follicular phase of the menstrual cycle. Seventeen naturally menstruating females (age 28.5 ± 7.3 years) completed local and global assessments of MTU function during two testing sessions separated over 24-72 hours. Local tests included Achilles’ tendon mechanical testing and isometric strength of ankle plantar flexors and knee extensors, whereas global tests included countermovement, squat, and drop jumps, and the isometric midthigh pull. Based on intraclass correlation coefficient (ICC) statistics, poor to excellent reliability was found for local measures (ICC: 0.096-0.936). Good to excellent reliability was found for all global measures (ICC: 0.788-0.985), excluding the eccentric utilisation ratio (ICC 0.738) and most rate of force development metrics (ICC: 0.635-0.912). Isometric midthigh pull peak force displayed excellent reliability (ICC: 0.966), whereas force-time metrics ranged from moderate to excellent (ICC: 0.635-0.970). Excluding rate of force development (coefficient of variation [CV]: 10.6-35.9%), global measures (CV: 1.6-12.9%) were more reproducible than local measures (CV: 3.6-64.5%). However, local metrics directly measure specific aspects of MTU function, and therefore provide valuable information despite lower reproducibility. The novel data reported here provides insight into the natural variability of MTU function within female athletes, which can be used to enhance the interpretation of other female athlete data, especially that which aims to investigate other aspects of variability, such as the menstrual cycle.

Video analysis research into the rugby league tackle typically uses technical criteria from coaching cues or tackle variables from rugby union. As such, the content validity and relevance could be questioned. A video analysis framework which establishes appropriate variables for rugby league is therefore required. The aim of this study was to adopt a 5-stage process to establish a video analysis framework for the rugby league tackle, which was content valid, relevant and reliable. The 5-stage process included 1) creation of draft variable list (video analysis framework), using available rugby tackle research, 2) expert group recruitment and critique, 3) refinement of video analysis framework to establish content validity, 4) response process validity task and agreement within expert group, 5) intra- and inter-reliability testing using Kappa statistics. The agreed video analysis framework comprised 6 phases including; tackle event, defensive start point, pre-contact, initial contact, post-contact and play the ball. Within the identified phases, 63 variables were established. The intra- and inter-reliability testing resulted in strong agreement (>0.81-1.0) within all phases. The 5-stage process allowed for the creation of a valid, relevant and reliable video analysis framework. The video analysis framework can be used in rugby league tackle research, categorising complex tackle events such as injurious or optimal tackles, improving both player welfare and performance. Furthermore, the application of the video analysis framework to future rugby league research will increase the coherence and usefulness of research findings.

Rugby league has a relatively high injury risk, with the tackle having the greatest injury propensity. The number of tackles players engage in, prior to injurious tackles may influence injury risk, which has yet to be investigated. Therefore, this study investigated if rugby league players are involved in more tackles (as either tackler or ball carrier) (i) in the 10 minutes, or (ii) 1-min periods prior to an injurious tackle-event, (iii) differences for ball carriers vs. tacklers, and (iv) forwards vs. backs. Video analysis was utilised to quantify the number and rate of tackles in the 10-min periods prior to 61 tackle-related injuries. One thousand two hundred and eighty 10-min periods where players were not injured, were used as matched-controls. Generalized mixed linear models were used to analyse mean total and rate for tackles. Injured players were involved in significantly fewer tackles during the 10-min period, yet significantly more tackles during the final minute prior to the injurious tackle-event, compared to non-injured players. There were no differences between ball carriers vs. tacklers during the 10-min period. Both injured position groups were involved in significantly more tackles in the final minute. Additional match data sources are needed to further inform injury preventive strategies of tackle events.

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 the current study was to investigate the anthropometric, body composition and fitness characteristics of female rugby league players by playing position. Data were collected on 27 players who were part of the English elite women's rugby league squad. Player assessments comprised anthropometric (stature and body mass), body composition (dual-energy X-ray absorptiometry) and fitness (lower-body power [countermovement jump (CMJ), 20 kg jump squat (JS) and 30 cm drop jump], 5, 10, 20, 30, and 40 m sprint, 505 agility, Yo-Yo intermittent recovery test level 1) measures. Players were classified into playing position (i.e., forwards and backs) prior to analysis. A multivariate analysis of variance (MANOVA) demonstrated significant (p<0.05) differences for body mass, stature, total fat, lean mass and percentage body fat between forwards and backs. Positional differences were also observed for speed, agility and lower-body power. Significant relationships were observed between total body fat and all fitness variables, and total lean mass was related to CMJ and JS peak power. This study provides comparative data for female rugby league forwards and backs. Body fat was strongly associated with performance and should therefore be considered in developing fitness characteristics. The relationship to match performance and trainability of these characteristics warrants further investigation.

INTRODUCTION: Markerless motion capture (MMC) is increasing in popularity among biomechanists because of the reduced data collection time and removal of subjects needing to wear tight, minimalist clothing [1]. However, gait analysis often requires subjects to walk or run at multiple speeds, such as in an incremental exercise test. The sensitivity of MMC to detect kinematic changes across speeds has yet to be thoroughly explored, so the aim of this study was to compare kinematic responses to changes in gait speed when measured with a widely used marker-based system versus a MMC system. METHOD: Fifteen healthy, adult participants walked on an instrumented treadmill (1,000 Hz; Gaitway3D; h/p/cosmos) at 3 and 5 km/h and ran at 10, 11, and 12 km/h. A 14-camera optoelectronic motion capture system (Oqus 7+, Qualisys) was used to collect marker data, where markers were placed according to Cappozzo et al. [2]. Markerless video data were collected synchronously with 12 high-speed video cameras (Miqus, Qualisys). Both systems were sampling at 100 Hz. Markerless data were exported to Theia3D for processing, before being exported to Visual3D for modelling alongside marker data. Gait events were determined using the kinetic data, which was the same for both motion capture systems. Kinematic data were exported to MATLAB to calculate changes in sagittal angular data between gait speeds. RESULTS: For walking (changes between 3-5 km/h), MMC demonstrated the capacity to measure similar changes in joint range of motion (ROM), peak flexion, and peak extension for hip, knee, and ankle joints (ICC[3,1] ≥ 0.892) when compared to marker-based data, and there were no significant differences between the change in joint kinematics between systems (p > 0.05). MMC also displayed moderate-to-excellent agreement for knee and ankle joint kinematics during running (changes between 10-11 and 11-12 km/h), including ROM and peak flexion/extension (ICC ≥ 0.626). However, the hip joint was less consistent, with poor-to-moderate agreement generally being found, especially in peak hip extension (ICC = 0.198 when comparing differences between 11-12 km/h). There were no significant differences between systems during running (p < 0.05). CONCLUSION: MMC was able to measure small changes in joint angles during walking at similar magnitudes to traditional marker-based motion capture, which is promising for clinical biomechanists and gait analysis clinics. However, MMC importantly performs less well when trying to measure joint angle changes during different running speeds, with varying results between lower limb joints. Researchers and practitioners should be cautious when interpreting sagittal-plane kinematic changes during running when employing MMC as the chosen method of motion capture. REFERENCES: [1] Kanko, RM et al. (2021) J Biomech;127:110665 [2] Cappozzo, A et al. (1995) Clin Biomech;10:171-8