Differences in Eccentric and Concentric Power During Squats Performed in Power, Hypertrophy and Strength Workouts

Abstract

Previous researchers have highlighted the beneficial effect of eccentric power output on concentric performance during resistance training movements utilizing the stretch-shortening cycle. However, it is unclear how both eccentric and concentric power are acutely affected by the workout scheme used. PURPOSE: The purpose of this study was to investigate the acute effects of manipulating load, repetitions and inter-repetition rest periods on average eccentric and concentric power output during back squats. METHODS: Seven male subjects (21.2 ± 1.9 years; 1.75 ± 0.35 m; 87.2 ± 13.3 kg) performed five sets of back squats in three different workouts designed for strength (STRENGTH: 90% 1-repetition maximum [1-RM]; 4 repetitions; 4 min rest), power (POWER: 75% 1-RM; 5 repetitions; 3 min rest) and hypertrophy (75% 1-RM; 10 repetitions; 90 s rest) in accordance with NSCA recommendations. The squats were performed on a force platform synchronized with a 3D motion analysis system, both sampling at 200 Hz. Power output was calculated as the product of the vertical component of the ground reaction force and the vertical velocity of the bar and was normalized to body mass2/3. The eccentric and concentric phases of each repetition were identified from the vertical displacement of the bar and power output was averaged during these phases to provide eccentric (APECC) and concentric power (APCON). APECC and APCON were then averaged across each set for all workouts. The data were analyzed using a three-way ANOVA with repeated measures. RESULTS: The mean 1-RM for the back squat was 8.30 ± 1.68 kg/kg2/3. APCON was greater than APECC regardless of the workout or set (mean difference = 9.09 W/kg2/3; p = 0.012), while greater power outputs were achieved during POWER compared to STRENGTH (mean difference = 6.87 W/ kg2/3; p = 0.024). Further analysis revealed that the difference between POWER and STRENGTH was greater for APECC compared to APCON (mean APECC difference = 8.19 W/kg2/3; mean APCON difference = 5.56 W/ kg2/3; p = 0.035). CONCLUSIONS: The load used during back squats has a substantial effect on average power, particularly during the eccentric phase of the movement. The number of repetitions and inter-repetition rest periods appear to have less of an impact on average power output.