Medicine & Science in Sports & Exercise:
F-12M Free Communication/Poster Exercise Testing
Zink, A J.1; Perry, A C. FACSM1; Sandler, D J.1; Bamel, S A.1; Signorile, J F.1
1University of Miami, Coral Gables, FL
The load required to maximize power output during the squat is a matter of some debate among strength and conditioning specialists.
To analyze the differences in peak power with changing loads during the performance of an explosive parallel squat, and to examine the associated changes in the force and velocity components under those loading conditions.
Twelve males experienced with weight-lifting (training history=11.17±5.75 years), performed the parallel squat at loads equivalent to 20, 30, 40, 50, 60, 70, 80, and 90 percent of their one repetition maximum (1 RM). Peak power (Pp), peak ground reaction force (Fp), peak barbell velocity (Vp), force at time Pp (FTP), velocity at time Pp (VTP), time between Fp and Pp (TFP), time between Pp and Vp (TVP) and time between Fp and Vp (TFV) were determined from force, velocity and power curves calculated using barbell velocity and ground reaction forces (GRF). Barbell velocity was measured by monitoring movement of a cable attached to the ends of the barbell. GRF was measured with a force plate. Sampling frequency for both was 60 Hz.
While no significant differences (p>0.05) were detected among loading conditions for Pp, the greatest Pp values were associated with loads of 40 and 50 percent of 1RM. Higher loads produced significantly greater Fp values than lower loads (p<0.05) in all cases except between midrange loads of 60–50, 50–40, and 40–30 percent of 1RM. Higher loads also produced greater FTP than lower loads for all comparisons except between 70–60, and 60–50 percent of 1RM. Higher percentage loads produced lower Vp and VTP values than lower percentage loads (p<0.05) in all cases except for comparisons between loads corresponding to 20–30, 70–80, and 80–90 percent of 1RM. No significant differences (p>0.05) were detected between loads for TFP, TVP, or TFV.
Changes in the magnitude of the force and velocity components contribute more than the relative timing of these components to the differences seen in Pp across loading conditions.