Why volleyball players jump higher

Abstract

The aim of this study was to describe the dynamics of force development and vastus lateralis electromyographical activity during vertical jumps performed by subjects with broad differences in jumping experience. To more easily identify these differences, male (21) and female (9) elite volleyball players were compared with male (12) and female (11) Physical Education students. The force developed (Kistler force plate) and electromyographical activity (Bioamplifier ML 131 ADI Instruments) at the surface of the vastus lateralis during vertical jumps (squat and countermovement jumps), as well as whole body composition (dual energy x-ray absorptiometry of DXA) were assessed in all subjects. Muscular mass in the lower limbs was calculated from the DXA scans, assuming that limb lean mass is equivalent to muscular mass. Volleyball players showed greaterjumping power and height due to their ability to reach a higher peak force, as well as their capacity to generate a greater rate of force development during thejumps (p<0.05). This allows the volleyball players to generate greater mean power and, consequently, reach more height (p<0.05). The time required to generate positive mechanical impulse tended to be lower in the volleyball players than in the Physical Education students. However, the differences observed did not reach statistical significance. Volleyball players generated greater negative mechanical impulse (mechanical impulse developed during the downward movement of the countermovement jump). In males, there was a close correlation between negative and positive mechanical impulse (r = -0.81, p<0.001). This study also suggested that volleyball players might utilise the mechanisms that boost the height reached in the vertical jump more efficiently, when the vertical jump is immediately preceded by a countermovement.