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.