Dr Mark Helme

The application of velocity-based training (VBT) protocols has increased in popularity through an increasing research evidence base. Specifically, velocity loss threshold training (VLT) has gained interest through the notion that equitable or greater gains in strength and power can be attained with fewer completed repetitions than traditional strength training. The current literature, however, does not reflect the chaotic and uncontrolled environments found in practice. Therefore, the current study sought to explore this notion using an in-situ research approach, applying a VLT intervention to an in-season men’s university Rugby Union programme. The RU squad (n=35) was randomly assigned to either a VLT (n= 18) or traditional resistance training programme (n= 14), matched for exercise selection and intensity. The Output Sports v2 device was used to provide both groups instantaneous visual feedback on concentric velocity, where the VLT group were halted mid-set when they experienced a 15 % decrement in velocity. There were no time effects on strength or power measures, indicating both programmes were effective in maintaining outcome measures, during the playing season. Insufficient numbers of participants met the inclusion criteria permitting post season, between group analysis. The data indicates the challenges of conducting in-situ, in-season research, specifically that which relies on extensive testing batteries. An application of a “testing is training” approach is advocated, whereby wearable technologies can capture performance data from scheduled activities that can inform decisions relating to changes in physical performance.

Recent trends have shown an increase in youth training intensification among those on talent development pathways, coinciding with greater prevalence of strength and conditioning (S&C) provision in sport-friendly independent schools. Despite this, limited data exist on the physical characteristics of sport scholars or the impact of structured S&C programmes, in these schools. Concurrent to this trend is the increased availability of technologies to capture physical performance data, specifically portable force plates. Therefore, this study aimed to quantify the force-time characteristics of sport scholars at a single independent school and analyse how these characteristics change within and between school years. Methods This study included 203 participants (61 females, 142 males) from Years 10 to 13 (mean age = 16.86 ± 6.31 years), specialising in Rugby, Basketball, Cricket (males), Football, and Netball (females). Fitness testing occurred at the start of each term (September, January, May), anthropometric data—mass, standing and seated height—were collected during the second and third tests to calculate maturational offset and predicted age at peak height velocity using the modified Mirwald equation. Force-time characteristics were assessed during the countermovement jump (CMJ) and isometric mid-thigh pull (IMTP) assessments using Hawkin Dynamics portable force plates. Results Conclusion This study provides novel benchmark data for sport scholars in CMJ and IMTP testing, previously unavailable in this context. Findings reveal distinct developmental trajectories between male and female athletes during late adolescence. Males demonstrated continued improvements in both dynamic and isometric force production up to age 18, whereas females showed stagnation or decline. No significant changes were observed in CMJ force-time phases, suggesting that concentric peak force production was the most important variable for increased jump height. These results underscore the need for differentiated training strategies tailored to sex-specific physiological responses, ensuring equitable development opportunities and optimised performance outcomes for adolescent athlet

Rugby League (RL) is an intermittent, high intensity, collision sport characterised by frequent accelerations and changes of direction (Gabbett et al., 2008). Leg strength has been associated with improved performance in both linear and change of direction speed (CODS) (Bret et al., 2002, Wisløff et al., 2004, Cronin and Hansen, 2005, McBride et al., 2009). Previous research has used bilateral methods of investigating this association, yet few studies have taken a unilateral approach to strength assessment. The aim of this study was to investigate the relationships between unilateral leg strength speed, momentum, change of direction speed and change of direction deficit, in RL players. Further understanding the interaction to different forms of strength and performance measures may better enable practitioners to prepare their athletes. It was hypothesized that increased leg strength would positive influence performance in sprint and CODS measures. With institutional ethical approval testing was conducted at the respective facilities of three participating Rugby League clubs (n = 50). Physiological testing was separated into two sessions the first being speed and change of direction assessment and the second collection of strength data. CODS was measured using the modified 5-0-5 test, speed was tested using a 20m linear sprint from a standing start. For both tests three trials were performed and the best result used for analysis. Unilateral leg strength was measured using the rear foot elevated split squat (RFESS) 5RM (Helme et al, under review). Strength data was calculated in both absolute and relative terms, linear speed was analysed at both 10m and 20m for time, mean velocity and mean momentum for each 10m section. CODS was analysed for time and also for change of direction deficit, (Nimphius et al., 2016). The mean absolute load achieved in the RFESS 5RM was 88.92 ±12.59kg, when expressed relative to body mass was 1.01 ±0.17kg/kg. Possibly to likely small negative associations were found to both change of direction times and change of direction deficits. Possibly small positive associations were observed between momentum and velocity, for the 10-20m section, but not for 0-10m. No correlations reached the alpha level of significance (p = <0.05) for absolute strength. A most likely or almost certain moderate negative relationship was found between CODS and relative leg strength (p= <0.05) and a likely moderate positive relationship to linear mean velocity between 10 and 20m. Almost certainly moderate (10-20m) or large (0-10m) negative relationships were observed with momentum in a linear sprint (p = >0.05). The data from this study suggests that absolute unilateral leg strength is not significantly related to sprinting or CODS performance. However, increasing relative unilateral leg strength is positively associated with increased change of direction speed and velocity, specifically between 10m and 20m. Furthermore, almost certainly large negative correlations were found between relative leg strength and momentum, which is at odds with the other findings of this study. Baker and Newton (2008) identified momentum as a significant contributor to performance in RL, particularly in winning collisions, which are in turn, essential for successful match outcomes. Practitioners may consider the use of relative unilateral leg strength to better understand the development of velocity and CODS in their athletes. This should be taken with caution though, as further investigation is required to better understand the interaction between relative strength and momentum.

The rear foot elevated split squat (RFESS) is a multi-joint, unilateral resistance exercise, commonly used in strength and conditioning (McCurdy, 2017). McCurdy, Langford et al. (2004) and McCurdy and Langford (2005) have previously reported the RFESS as a reliable measure of unilateral leg strength (1RM ICC, 0.97- 0.99). To further enhance the proposed frequency of use and reliability as both a single and multiple repetition test of leg strength, it is pertinent to quantify the kinetic and kinematic characteristics of the exercise. No study, to date, has yet analysed the intra-set differences in kinetic and kinematic parameters, in a multi-repetition test of leg strength. The aim of this study was to firstly quantify the kinetic and kinematic characteristics of the RFESS 5RM test protocol. Secondly to profile the intra-set differences between repetitions. METHODS 26 volunteers were recruited, with institutional ethical approval (age = 23.8 ±4.6 years, mass = 88.1 ±10.7kg, height = 1.79±0.1m), all subjects were engaged in a structured strength and conditioning program. Participants were required to undergo an incremental loading test until maximal load was achieved. Kinetic data was collected from the front and rear foot through two independent Kistler 9827C force plates at 1000Hz (Kistler Group, Winterthur, Switzerland), as depicted in figure 1. Kinematic data was captured through Qualysis Track Manager System at 250Hz (Qualysis AB, Gothenburg, Sweden) using 10 cameras (six ceiling mounted and four, floor mounted).Data was exported to a bespoke R code for this project. Magnitude based inferences were made on intra-set differences between repetitions for each of the kinetic and kinematic variables. RESULTS The mean load lifted was 84kg ±16.8kg (0.96 ±0.18 kg/kg). The mean vertical displacement of the bar was 0.38 ± 0.06m, mean concentric velocity was 0.32 ±0.05m/s and peak concentric velocity was 0.49 ±0.11m/s. The mean vertical ground reaction force (vGRF) of the lead foot was 1432.54±200.87N, (1.66 ±0.20BW). The lead foot produced 83.53±4.03% of total vGRF There were unclear differences in all kinetic variables between all repetitions, except for peak (vGRF) of the lead foot only (1.90±0.28BW) of Repetition 5, which was very likely larger. Repetitions 1 and 2 were likely to very likely to have higher mean concentric velocities (MCV) than repetitions 4 and 5. Figure 1: Data collection procedures for the RFESS 5RM protocol DISCUSSION The RFESS 5RM produces mean and peak concentric vGRF of 1.66±0.20 BW and 1.84±0.24BW, which approximately equals the values reported by (Ebben and Jensen, 2002) for a bilateral squat. The inconsistent inferential findings across the set suggest that the final repetition may be different to repetitions 1-4, generating the highest peak force, largest vertical displacement and slowest MCV. Such findings indicate that repetition 5 represents the maximal effort of that set and the maximal protocol. CONCLUSION The RFESS 5RM is valid and reliable method of measuring unilateral leg strength. A multi-repetition protocol can be used to determine maximal strength, yet intra-set differences may not exist prior to completion of the final repetition

The purpose of this study was to examine the Rear foot elevated split squat (RFESS) five repetition maximum test as a valid and reliable field method for measuring unilateral leg strength symmetry. With institutional ethical approval, 26 subjects (age = 23.8 ±4.6 years, mass = 88.1 ±10.7kg, height = 1.79±0.1m) with a minimum two years strength and conditioning experience were recruited. Following a familiarisation, session subjects performed an incremental 5 repetition maximum (RM) protocol on both legs, on two occasions where 3D motion and force data were collected. excellent reliability was found (ICC = 0.93 CL 0.88-0.96) in the load achieved between tests (mean load =0.96 ±0.18 kg/kg). Moderate reliability of bar load symmetry was found between test and re-test conditions correlation (ICC = 0.73, 0.33-0.91) with no proportional bias between sessions. Validation of the exercise was measured using a Pearson correlation between asymmetries in vertical ground reaction forces of the lead foot and bar load. When all maximal trials, from both test conditions, were analysed, a most likely large positive correlation (0.57, 0.30 to 0.76) were found for mean lead foot vGRF. When a threshold level of load symmetry (96.54% - 103.46%) was applied, a most likely large positive correlation (r = 0.59, 0.14-0.84) between symmetry in lead foot vGRF was found in subjects who exceeded this limit. Findings of this study suggest the RFESS is a valid and reliable measure of unilateral leg strength symmetry. Practitioners are recommended to use this exercise to investigate the strength symmetry of athletes, but are guided to note that a threshold level of symmetry (96.54% - 103.46%) may be required to have been exceeded to indicate a true difference in vGRF production

Objectives The aim of this study was to analyse the relationship between unilateral leg strength, associated asymmetries and the injuries suffered by sub-elite Rugby League (RL) players in one competitive season. Design A prospective cohort design was used. Method Unilateral leg strength was measured using the rear foot elevated split squat five repetition maximum test. Injuries were recorded using the Orchard classification system and were used to quantify relative risk (RR), mean severity, burden, player availability and survival time. Results No measures of leg strength were related to RR, relative leg strength was found to have a significant, but not meaningful correlation with total time lost to lower body injury, lower body injury burden and lower body injury survival time. Conclusions The data from the current study indicates a possible positive effect of increasing relative leg strength for injury outcomes in sub-elite RL players. This supports a heuristic that multi-joint lower body strength training for RL players has a potential dual effect of enhancing physical performance and reducing injury time loss, with minimal risk of harm.

The purpose of the study was to determine the unilateral nature of the rear foot elevated split squat (RFESS). Specifically, the production of force by the rear leg was examined to better understand its role, if any, toward successful completion of the exercise. Male volunteers were recruited, (n = 26, age = 23.8 ±4.6 years, mass = 88.1 ±10.7kg, height = 1.79±0.1m), who were recreationally trained and engaged in a structured strength and conditioning program including both bilateral and unilateral exercise and had at least two years supervised training experience. Subjects participated in an incremental five repetition maximum protocol, following familiarisation. Kinetic data was recorded via two independent force plates, one integral to the floor and the second mounted on top of solid weightlifting blocks. Kinematic data was captured through three-dimensional motion analysis. A total of 715 repetitions were analysed, the mean contribution of the lead foot to total vertical force production was 84.36 ±3.6%. An almost certainly small positive correlation (rho = 0.25, CI 0.18, 0.33), was found between percentage of force produced by the lead foot, with increasing exercise intensity. A most likely trivial, non-significant correlation (rho = -0.01, CI -0.09,0.06) with rear foot force production, representing the mass of the rear leg. Data from this study does not indicate that the rear foot contributes to the kinetic demands of the exercise and therefore suggests that the RFESS is a valid unilateral exercise.

Rugby League (RL) is an intermittent, collision, invasion game, played internationally at professional, semi-professional and amateur level. The physiological attributes required for RL performance include, aerobic and anaerobic power, speed, acceleration, momentum, change of direction speed (CODS), strength, power and technical skill. Professional clubs operating in the Super League, develop academy players, as a method of talent development. However, not all players make the transition to senior, professional status, frequently required to leave this environment and participate at the semi-professional level. This study sought to better understand the physiological differences between these two levels, affording a better understanding of the career transition faced by academy graduates. The variables of examination were unilateral leg strength, strength symmetry, linear and change of direction speed. It was hypothesised that there would be significant differences between all variables. Rugby league players (n = 50), recruited from three different clubs, were used to investigate the physiological differences in unilateral leg strength and speed, both linear and COD. Tests of unilateral leg strength (rear foot elevated split squat 5RM, Helme et al, ePUB) and speed (20m sprint, modified 5-0-5 test) were separated by 48 hours. A magnitude based decision approach was used to determine between group differences in all variables measured. Semi-professional players were significantly heavier (+7kg, p =0.03, possibly moderate difference) than academy players, but there was no difference in height. No significant differences between groups in unilateral leg strength, either in absolute load or relative to body mass, nor was there any difference in strength symmetry. Analysis of linear sprint speed identified no differences between academy and semi-professional players between 0 and 10m, of a 20m sprint, however, between 10and 20m academy players had a possibly moderately higher mean velocity (7.57m/s vs 7.7m/s, p =0.35). Despite the difference in body mass no significant differences in momentum was observed. There were no significant differences between either group for change of direction speed or change of direction deficit. Academy and Semi-professional players exhibit comparable qualities with respect to unilateral leg strength, speed and change of direction ability. Such findings suggest that a career transition from academy to semi-professional Rugby League is an appropriate step, from a physiological perspective. However anthropometrically, the differences in body mass between groups suggests that such progression may not be so advantageous. Whilst both groups have equitable abilities, semi-professional players can perform these tasks at a significantly larger body mass, which is beneficial in collision sports. It should be concluded then, that in the transition to exit academy rugby league environments players should be focused on a strategy to simultaneously develop speed and change of direction ability, whilst accumulating greater lean body mass.

The purpose of this study was to examine the validity and reliability of the Rear Foot Elevated Split Squat (RFESS) five repetition maximum (5RM) test as a field method for measuring unilateral leg strength symmetry. As a validated method of testing symmetry, the RFESS 5RM may be used by Strength and Conditioning coaches and sports medicine staff to measure the presence of imbalances with minimal equipment and time. 26 subjects (age = 23.8 ±4.6 years, mass = 88.1 ±10.7kg, height = 1.79±0.1m) with a minimum two years strength and conditioning experience were recruited. Following a familiarization session, subjects performed an incremental five repetition maximum (5RM) protocol on both legs, on two occasions where 3D motion and force data were collected. Moderate reliability of bar load symmetry was found between test and re-test conditions correlation (ICC = 0.73, 0.33-0.91) with no proportional bias between sessions. Validation of the exercise was analyzed using a correlation between asymmetries in mean set vertical ground reaction forces (vGRF) of the lead foot during the concentric phase, with bar load. When all maximal trials, from both test conditions, were analyzed, a most likely large positive correlation (0.57, 0.30 to 0.76) were found for mean set concentric lead foot vGRF. When a threshold level of load symmetry (96.54% - 103.46%) was applied, a most likely large positive correlation (r = 0.59, 0.14-0.84) between symmetry in lead foot vGRF was found in subjects who exceeded this limit. Conversely, analysis of subjects within the threshold produced unclear correlations. Findings of this study suggest the RFESS is a valid and reliable measure of unilateral leg strength symmetry. Practitioners are recommended to use this exercise to investigate the strength symmetry of athletes, but are guided to note that a threshold level of symmetry (96.54% - 103.46%) may be required to have been exceeded to indicate a true difference in vGRF production.

The rear foot elevated split squat (RFESS) is a multi-joint, unilateral resistance exercise, commonly used in strength and conditioning McCurdy (2017). McCurdy, Langford et al. (2004) and McCurdy and Langford (2005) have previously reported the RFESS as a reliable measure of unilateral leg strength (1RM ICC, 0.97- 0.99). To further enhance the proposed frequency of use and reliability as both a single and multiple repetition test of leg strength, it is pertinent to quantify the kinetic and kinematic characteristics of the exercise. No study, to date, has yet analysed the intra-set differences in kinetic and kinematic parameters, in a multi-repetition test of leg strength. The aim of this study was to firstly quantify the kinetic and kinematic characteristics of the RFESS 5RM test protocol. Secondly to profile the intra-set differences between repetitions. 26 volunteers were recruited, with institutional ethical approval (age = 23.8 ±4.6 years, mass = 88.1 ±10.7kg, height = 1.79±0.1m), all subjects were engaged in a structured strength and conditioning program. Participants were required to undergo an incremental loading test until maximal load was achieved. Kinetic data was collected from the front and rear foot through two independent Kistler 9827C force plates at 1000Hz (Kistler Group, Winterthur, Switzerland), as depicted in figure 1. Kinematic data was captured through Qualysis Track Manager System at 250Hz (Qualysis AB, Gothenburg, Sweden) using 10 cameras (six ceiling mounted and four, floor mounted).Data was exported to a bespoke R code for this project. Magnitude based inferences were made on intra-set differences between repetitions for each of the kinetic and kinematic variables. The mean load lifted was 84kg ±16.8kg (0.96 ±0.18 kg/kg). The mean vertical displacement of the bar was 0.38 ± 0.06m, mean concentric velocity was 0.32 ±0.05m/s and peak concentric velocity was 0.49 ±0.11m/s. The mean vertical ground reaction force (vGRF) of the lead foot was 1432.54±200.87N, (1.66 ±0.20BW). The lead foot produced 83.53±4.03% of total vGRF There were unclear differences in all kinetic variables between all repetitions, except for peak (vGRF) of the lead foot only (1.90±0.28BW) of Repetition 5, which was very likely larger. Repetitions 1 and 2 were likely to very likely to have higher mean concentric velocities (MCV) than repetitions 4 and 5. The RFESS 5RM produces mean and peak concentric vGRF of 1.66±0.20 BW and 1.84±0.24BW, which approximately equals the values reported by (Ebben and Jensen, 2002) for a bilateral squat. The inconsistent inferential findings across the set suggest that the final repetition may be different to repetitions 1-4, generating the highest peak force, largest vertical displacement and slowest MCV. Such findings indicate that repetition 5 represents the maximal effort of that set and the maximal protocol. The RFESS 5RM is valid and reliable method of measuring unilateral leg strength. A multi-repetition protocol can be used to determine maximal strength, yet intra-set differences may not exist prior to completion of the final repetition. Practitioners should consider this information when evaluating the efforts of athletes during this exercise.

Objective The aim of this review was to synthesize the current understanding relating to the risks of lower body functional asymmetry with injury in athletic populations. Methods An iterative data mining and sampling approach was used to construct a search phrase from key words, which were used to identify studies within SPORTdiscus, Medline and Academic Search Complete databases. Additional references were sourced from the reference lists of these articles Results After screening, 31 papers were reviewed, from an initial search identifying 302 possible studies. A total of 6228 participants were involved in the studies, of which soccer players were the most observed sporting demographic (n =2171). Of the 31 studies reviewed eight found no statistical association between lower limb asymmetry and injury risk, 10 studies provided partial statistically significant evidence and a further 10 provided statistically significant statistical links. Conclusion Overall moderate to lower quality evidence for functional asymmetry as a risk factor for injury in sport was observed. While the possibility of a relationship between lower limb functional asymmetry and injury risk cannot be ruled out, further higher quality investigations, adopting standardised methodologies, is required.

Leg strength and multidirectional speed qualities have repeatedly been linked with increased performance during Rugby League (RL) match play and associated with career attainment. However, very little of this evidence for strength has been gained through unliteral measurements with no study available that has examined the impact of strength asymmetry, in this population, on speed qualities in RL players. Therefore, this study examined the association between unilateral strength and as a novel development the subject with the most extreme asymmetry was identified for further analysis. 50 RL players undertook the rear foot elevated split squat five repetition maximum, 20 m linear sprint and modified 505 change of direction test. The mean leg strength for the group was 88.92 ±12.59 kg, when divided by body weight the mean relative strength (REL) was 1.03 ±0.17 kg/kg and the mean asymmetry was 3.21 ±5.70 %. The participant with the greatest asymmetry (subject A) had an imbalance of 33% and a mean leg strength of 75 kg (REL = 0.78 kg/kg) and a body mass one standard deviation above the group mean. Analysis of the group’s data and that of subject A did not indicate that leg strength asymmetry was either frequent or harmful, with respect to speed performance. However, relative leg strength was associated with both improved linear and multidirectional speed. Practitioners are recommended to prioritise the development of relative leg strength and disregard the aspiration for between leg performance symmetry.