(1) FORCE PRODUCTION DIFFERENCES BETWEEN STRONGER AND WEAKER MEN DURING TRADITIONAL AND ACCENTUATED ECCENTRIC LOADED BACK SQUATS

Purpose: To compare the force production characteristics of stronger and weaker resistance-trained men during traditional (TRAD), maximal accentuated eccentric loaded (AEL-MAX) and supramaximal AEL (AEL-SUPRA) back squat sets. Methods: 15 resistance-trained men completed a one repetition maximum (1RM) back squat during an initial testing session and were divided into stronger (n=8, age=25.3±5.1 years, height=172.8±5.6 cm, body mass=80.2±11.0 kg, relative 1RM back squat=2.24±0.12 kg/kg) and weaker (n=7, age=23.6±1.7 years, height=182.9±6.2 cm, body mass=91.4±12.4 kg, relative 1RM back squat=1.76±0.13 kg/kg) groups based on their ability or inability to back squat twice their body mass, respectively. During the following three testing sessions, each subject performed three back squat repetitions with 50, 60, 70, and 80% of their 1RM during TRAD, AEL-MAX, or AEL-SUPRA conditions. While the TRAD squats were performed with the same load during the eccentric and concentric phases of each repetition, the AEL-MAX and AEL-SUPRA conditions required the subjects to perform the eccentric phase of the first repetition with a load equivalent to either 100 or 110% of their 1RM, respectively, before performing the concentric phase and then the eccentric and concentric phases of the remaining two repetitions with the same loads as the TRAD session. The additional load during the first repetition during the AEL-MAX and AEL-SUPRA sets was added using weight releasers. The back squats were performed on a force platform and the force-time data were used to calculate the braking and propulsion net mean force and phase duration of each repetition. The average performance across each set for the variables was used for statistical comparison. A series of 2 (strength) x 4 (load) repeated measures ANOVA were used to compare the force production characteristics between the stronger and weaker subjects during each squat condition. Results: The braking and propulsion characteristics produced by each group are displayed in Table 1. Except for propulsion duration favoring the strong group (p=0.030), there were no significant differences in any other braking or propulsion variable during TRAD squats. In contrast, the strong group displayed significantly greater braking (both p=0.016) and propulsion (p=0.008, p=0.049) net mean force as well as a significantly shorter propulsion duration (both p=0.014) during the AEL-MAX and AEL-SUPRA conditions, respectively. Conclusions: Despite no differences during TRAD squat sets, stronger men produced greater braking and propulsion forces compared to weaker men during AEL squat sets. While braking forces between groups were produced over similar durations, the stronger group performed the propulsion phase faster than the weaker group across all conditions. Practical Applications: Stronger men may receive a greater braking and propulsion stimulus compared to weaker men suggesting that AEL may be considered an advanced training strategy. Acknowledgements: None