Kinetic variables and vertical stiffness of female volleyball players during a vertical jump

Abstract

Problem statement.Vertical jump is an essential motor skill in many sports, especially in volleyball where the total number of jumps performed by a player during training and games is high. Lower-extremity stiffness seems to greatly affect the storage and utilization of elastic energy during stretch-shortening cycles and the rate of force development; higher levels of lower-extremity stiffness seem to be necessary for higher vertical jump height. Approach. A total of eight female volleyball players (16.00 ± 1.07 years, 166.00 ± 4.04 cm, 57.02 ± 8.73 kg) and eight female sedentary participants (15.13 ± 1.36 years, 161.13 ± 6.71 cm, 50.70 ± 5.42 kg) volunteered to participate in this study. They performed countermovement jumps with and without arm swing; kinetic variables and vertical stiffness were analyzed. Purpose. The aim of this investigation was to analyze kinetic variables and vertical stiffness of adolescent female volleyball players during a vertical jump. Results. Significant differences between volleyball players and sedentary participants were observed in flight height, maximum vertical displacement of the center of mass, acceleration impulse, average power, peak power, and vertical stiffness (p < 0.01). No significant differences were observed in average force or peak force. Female volleyball players had significantly higher values of almost all kinetic variables analyzed compared to sedentary subjects of the same age range. However, because they had greater vertical displacement of the center of mass without differences in the peak force, they showed a significantly lower vertical stiffness values. Conclusions. A specific training to increase vertical stiffness can make volleyball players more impulsive subjects and lead to better use of elastic energy during the stretch-shortening cycle, which will increase vertical jump height.