The Influence of an additional load on time and force changes in the ground reaction force during the countermovement vertical jump

摘要

The aim of this study was to determine how an additional load influences the force-vs-time relationship of thecountermovement vertical jump (CMVJ). The participants that took part in the experiment were 18 male universitystudents who played sport recreationally, including regular games of volleyball. They were asked to perform a CMVJwithout involving the arms under four conditions: without and with additional loads of 10%, 20%, and 30% of theirbody weight (BW). The vertical component of the ground reaction force (GRF) was measured by a force plate. The GRFwas used to calculate the durations of the preparatory, braking, and acceleration phases, the total duration of the jump,force impulses during the braking and acceleration phases, average forces during the braking and acceleration phases,and the maximum force of impact at landing. Results were evaluated using repeated-measures ANOVA. Increasing theadditional load prolonged both the braking and acceleration phases of the jump, with statistically significant changes inthe duration of the acceleration phase found for an additional load of 20% BW. The magnitude of the forcesystematically and significantly increased with the additional load. The force impulse during the acceleration phase didnot differ significantly between jumps performed with loads of 20% and 30% BW. The results suggest that the optimaladditional load for developing explosive strength in vertical jumping ranges from 20% to 30% of BW, with this valuevarying between individual subjects.