Validity and reliability of the rear foot elevated split squat 5 repetition maximum to determine unilateral leg strength symmetry

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 ± 10.7 kg, height = 1.79 ± 0.1 m) 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

A multi-club analysis of the locomotor training characteristics of elite female soccer players

Objective: Quantifying differences in locomotor characteristics of training between two competition levels and between training days within elite female soccer players. Methods: Foot-mounted inertial measurement unit (Playermaker) data were collected from 293 players from three Women’s Super League (WSL; n = 76) and eight Women’s Championship (WC; n = 217) teams over a 28-week period. Data were analysed using partial least squares correlation analysis to identify relative variable importance and linear mixed effects models to identify magnitude of effects. Results: WSL players performed more high-speed running distance (HSR; &gt;5.29 m∙s −1), sprint distance (SpD; &gt;6.26 m∙s −1), acceleration (ACC; &gt;3 m∙s −2) and deceleration (DEC; &lt;-3 m∙s −2) distance than WC players. The largest difference between WSL and WC in HSR and HSR per minute occurred on MD-4, (354.7 vs. 190.29 m and 2.8 vs. 1.7 m∙min −1). On MD-2, WSL players also covered greater SpD (44.66 vs. 12.42 m), SpD per minute (0.38 vs. 0.11 m∙min −1) and HSR per minute (1.67 vs. 0.93 m∙min −1). Between training days both WSL and WC teams reduced HSR and SpD but not ACC and DEC distance from MD-4 to MD-2, with MD-4 the highest training day of the week. Conclusion: MD-4 is a key training day discriminating between competitive level. HSR and SpD volume and intensity is tapered in WSL and WC players, however there is less clear taper of ACC or DEC. As such, WC teams could increase the volume and intensity of HSR on MD-4 to mimic locomotor activities of those at a higher standard.</p

Concurrent validity and between-unit reliability of a foot-mounted inertial measurement unit to measure velocity during team sport activity

The concurrent validity and between-unit reliability of a foot-mounted inertial measurement unit (F-IMU) was investigated during linear and change of direction running drills. Sixteen individuals performed four repetitions of two drills (maximal acceleration and flying 10 m sprint) and five repetitions of a multi-directional movement protocol. Participants wore two F-IMUs (Playermaker) and 10 retro-reflective markers to allow for comparisons to the criterion system (Qualisys). Validity of the F-IMU derived velocity was assessed via root-mean-square error (RMSE), 95% limits of agreement (LoA) and mean difference with 95% confidence interval (CI). Between-unit reliability was assessed via intraclass correlation (ICC) with 90% CI and 95% LoA. The mean difference for instantaneous velocity for all participants and drills combined was −0.048 ± 0.581 m ∙ s −1, the LoA were from −1.09 to −1.186 m ∙ s −1 and RMSE was 0.583 m ∙ s −1. The ICC ranged from 0.84 to 1, with LoA from −7.412 to 2.924 m ∙ s −1. Differences were dependent on the reference speed, with the greatest absolute difference (−0.66 m ∙ s −1) found at velocities above 7 m ∙ s −1. Between-unit reliability of the F-IMU ranges from good to excellent for all locomotor characteristics. Playermaker has good agreement with 3D motion capture for velocity and good to excellent between-unit reliability.</p

Anthropometric, speed and endurance characteristics of English academy soccer players: Do they influence obtaining a professional contract at 18 years of age

This study evaluated the anthropometric, speed and endurance characteristics of English academy soccer players, comparing players who obtained a ‘professional’ contract at 18 years old with those that did not (‘academy’); 443 male academy soccer players from an English professional club undertook anthropometric (height and body mass), speed (10 and 20 m sprint) and endurance (Yo-Yo intermittent endurance test level 2 [Yo-Yo]) assessments between 2005 and 2012. Significant improvements with age were found for speed and endurance at each annual age group up until U18 age category. Significant differences were only observed between ‘professional’ and ‘academy’ players for 10 m (p = 0.003, η2 = 0.01) and 20 m (p = 0.001, η2 = 0.01) speed at U16 and U18 and Yo-Yo performance (p = 0.001, η2 = 0.12) at U18 age category. Practitioners should use speed and endurance assessments for monitoring physical development of players rather than for talent identification purposes

Importance of physical qualities for speed and change of direction ability in elite female soccer players.

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

A Kinetic and Kinematic Analysis of The Rear Foot Elevated Split Squat 5RM Test

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

A comparison of physiological differences between academy and semi-professional Rugby League players

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

A Kinetic and Kinematic Analysis of The Rear Foot Elevated Split Squat Five Repetition Maximum Test

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 repetitio