The Influence of an Additional Load on Time and Force Changes in the Ground Reaction Force During the Countermovement Vertical Jump

Frantisek Vaverka,Zlatava Jakubsova,Matej Supej,David Zahradnik,Jaroslav Uchytil,Daniel Jandacka,Roman Farana,Janez Vodicar

doi:10.2478/hukin-2013-0059

Frantisek Vaverka, Zlatava Jakubsova + Show 6 more

Open Access

https://doi.org/10.2478/hukin-2013-0059

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Abstract

The aim of this study was to determine how an additional load influences the force-vs-time relationship of the countermovement vertical jump (CMVJ). The participants that took part in the experiment were 18 male university students who played sport recreationally, including regular games of volleyball. They were asked to perform a CMVJ without involving the arms under four conditions: without and with additional loads of 10%, 20%, and 30% of their body weight (BW). The vertical component of the ground reaction force (GRF) was measured by a force plate. The GRF was 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 the additional load prolonged both the braking and acceleration phases of the jump, with statistically significant changes in the duration of the acceleration phase found for an additional load of 20% BW. The magnitude of the force systematically and significantly increased with the additional load. The force impulse during the acceleration phase did not differ significantly between jumps performed with loads of 20% and 30% BW. The results suggest that the optimal additional load for developing explosive strength in vertical jumping ranges from 20% to 30% of BW, with this value varying between individual subjects.

Highlights

This research focused on the effects of placing an additional load inside a special vest on the countermovement vertical jump (CMVJ)
The jump height (JH) when jumping with additional loads systematically decreased by about 4 cm when the additional load increased by 10% body weight (BW) (JH 0.385 m was reached without the load and 0.344 m, 0.309 m, and 0.276 m with the loads 10%, 20%, and 30% BW, respectively)
We found that the values of the average forces during the braking phase (BP) (FBA) and acceleration phase (AP) (FAA) increased significantly with increasing the additional load

Summary

Introduction

This research focused on the effects of placing an additional load inside a special vest on the countermovement vertical jump (CMVJ). The CMVJ most closely approximates natural jumping, and placing such an additional load does not fundamentally hinder the technique of the jump. The CMVJ is considered to be a suitable tool for both strength training itself and assessing the effectiveness of training. Numerous scientific studies have used jumping to investigate how various factors influence the development of maximal strength and power output during jumping (Bobbert et al, 1996; Bosco and Komi, 1981). Comparisons of the CMVJ and squat jump (SJ) have indicated that training that includes countermovement has a greater effect on the development of explosive strength (Cormie et al, 2009; Walshe et al, 1998). The combination of muscle activities in eccentric contractions at a braking phase during the lowering of the body

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