Acute effects of assisted jumping on muscle activation and jump performance

Introduction: Research has shown that assisted jumping results in an acute performance enhancement, however the underlying mechanisms of this are unclear. Purpose: To investigate lower body muscle activation and jump performance following assisted jumping. Methods: Eight collegiate female volleyball players (19.11 ± 1.05 yrs.; 175.99 ± 7.52 cm; 75.47 ± 10.88 kg) completed 2 experimental conditions (0% bodyweight or 40% bodyweight reduction (BWR)). For assisted jumping, participants wore a harness with elastic cords stretched to the ceiling by a rope and attached to their hips. In each trial, participants performed 5 plyometric countermovement jumps (CMJ), rested for 1 minute, then performed 3 individual bodyweight CMJ separated by 15 seconds rest. Electromyography was used to measure concentric and eccentric root mean square (RMS) amplitude of the gluteus maximus, vastus lateralis, and gastrocnemius lateralis prior to take-off. Vertical jump performance variables of impulse, jump height, takeoff velocity, relative ground reaction force, and relative peak power were collected on a force plate. Results: ANOVA for EMG RMS showed no 3 way interaction but there was a 2 way interaction of muscle x action for each muscle. Concentric actions of all muscles were greater than eccentric: gluteus maximus concentric 0.11 ± 0.03mV vs. eccentric 0.02 ± 0.01mV; vastus lateralis concentric 0.43 ± 0.09mV vs. eccentric 0.10 ± 0.03mV and gastrocnemius lateralis concentric 0.29 ± 0.08mV vs. eccentric 0.06 ± 0.04mV. There was no main effect for any performance variable. Conclusions: Based on the findings of the current study, there does not appear to be an acute PAP effect of assisted jumping on subsequent bodyweight countermovement vertical jumping in highly trained female volleyball players.