Load-Power Relationships for High-Speed Knee Extension Exercise

Chen, L, Davison, SW, Selimovic, EA, Mueller, RE, Beatty, SR, Carter, KA, Parmar, PJ, Symons, TB, Pantalos, GM, and Caruso, JF. Load-power relationships for high-speed knee extension exercise. J Strength Cond Res 33(6): 1480-1487, 2019-Seventy subjects did 4 knee extensor workouts with their left legs to assess load-power relationships produced on a high-speed trainer (HST; Newnan, GA, USA). Each workout is composed of 4 sets done on the HST at a different load (1, 4.4, 6.7, 9 kg). A Latin Squares Design determined load sequence per workout. Average power (AP) and peak power (PP) and those same values normalized to body mass (BM) and fat-free mass (AP/BM, PP/BM, AP/FFM, PP/FFM) were each analyzed with 2 (gender) × 4 (load) analysis of variances, with repeated measures for load. We assessed relationships between normalized loads and AP and PP values with correlation coefficients. Average power results revealed a significant interaction, with men > women at 9 kg. Peak power/body mass also yielded an interaction, with women > men at 6.7 and 9 kg. Average power/fat-free mass and PP/FFM each produced interactions, with women > men at 4.4, 6.7, and 9 kg. Correlation coefficients showed significant (r = 0.80-0.82) relationships between normalized loads and AP and PP values. In conclusion, the very low inertial resistance to initiate each repetition on this novel device may in part explain our PP/BM, AP/FFM, PP/FFM results, in which higher values were achieved by women. Our practical applications imply that the low inertial resistance for HST repetitions negates male size and strength advantages typically seen when power is measured.