Abstract

The purpose of this research was to determine the effect of the intensity of countermovement on vertical jump performance. Three conditions of vertical jumps involving arms were used to control the countermovement’s intensity: a) Vertical jumps starting from the upright position (CMJ + S), b) based on a previous jump where the drop height was regulated by the participant, (DJ- AR) and c) starting from a previous maximum jump (DJ- M). 28 athletes practicing different sports, where vertical jumping is a basic skill, were involved in this study. A force platform, operating at 500 Hz and temporally synchronised to a video camera which recorded the sagittal plane of the jumps on the platform at 210 Hz, were used. The vertical acceleration of the CM was determined from the net vertical force and the mass of the jumper. Successive vertical velocity and positions were calculated by integration of the vertical components of the acceleration-time and velocity-time functions respectively. The integration constants were determined by video images (2D). The results have shown that when jumps with drop heights exceeding 0.39 ± 0.05 m were performed, peak power during the propulsive phase, vertical impulse and jump height was significantly reduced (p < 0.001), which means that performance is reduced during the propulsive phase.