An analysis of peak power, ground reaction force and velocity during the squat exercise performed at different loads

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Exercise and Sport Sciences

First Committee Member

Joseph Signorile - Committee Chair


There currently exists a debate among strength and conditioning specialists concerning the most effective training methods for maximizing gains in power during weight-training. The primary purpose of this study was to analyze the changes in peak power under different loads during performance of the parallel squat exercise. The study also examined the changes in the force and velocity components contributing to peak power during these loading conditions. Twelve healthy males, experienced in performing the parallel squat movement (11.17 +/- 5.75 years), performed this motion at loads equivalent to 20, 30, 40, 50, 60, 70, 80, and 90 percent of their one repetition maximum (1RM). Peak power (PP), peak ground reaction force (PGRF), peak barbell velocity (PV), force at time PP (FPP), velocity at time PP (VPP), time between PGRF and PP (TFP), time between PP and PV (TPV) and time between PGRF and PV (TFV) were determined from force, velocity and power curves calculated using barbell velocity and GRF. Barbell velocity was measured by monitoring movement of cables attached to each end of a barbell and GRF was measured using a force plate. Changes in both variables were measured continuously at a sampling frequency of 60 Hz. No significant differences in PP were detected between loads (p > 0.05), however, the greatest PP values were associated with loads of 40 and 50 percent of 1RM. Higher percentage loads produced greater PGRF and FPP values than lower percentage loads (p < 0.05) in all cases except between loads corresponding to 60--50, 50--40, and 40--30 percent of 1RM for PGRF and 70--60, and 60--50 percent of 1RM for FPP respectively. Higher percentage loads produced lower PV and VPP values than lower percentage loads (p < 0.05) in all cases except between loads corresponding to 20--30, 70--80, and 80--90 percent of 1RM for both PV and VPP. No significant differences (p > 0.05) were detected between loads for TFP, TPV, or TFV. In conclusion, the magnitude of the peaks in the force and velocity curves were determined to play a larger role in differences in PP across loads than the time at which these peaks in the force and velocity curves occurred.


Education, Physical

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