Effects of Plyometric Exercise Training with Optimal Drop Heights on Reactive Strength, Maximal Strength, and Vertical Stiffness in Junior Basketball Players: A Randomised Controlled Trial

Abstract

This study examined the effects of 8 weeks of low-to-moderate intensity plyometric training with optimal drop heights on maximal isometric strength, vertical stiffness, and reactive strength in junior male basketball players. Participants were randomly divided into training (n = 20) and control (n = 20) groups from 3 teams with same division in the state league. Before and after 8 weeks of training, the drop jump (DJ) and isometric mid-thigh pull (IMTP) tests were performed to evaluate force-time measures. The optimal drop height was determined as the height that provided the highest reactive strength index (RSI). The ground contact phase during the DJ was divided into 2 subphases, braking and propulsion, for a detailed analysis of force-time curves. The analyses revealed that plyometric training significantly improved RSI (p < 0.001, Cohen’s d = 1.507), ground contact (p < 0.001, d=–1.255), braking (p = 0.001, d=–1.066) and propulsion phase (p < 0.001, d=–1.078) time. Significant improvements were observed in the peak vertical ground reaction force (p < 0.001, d = 1.715), peak centre of mass displacement (p = 0.005, d=–0.989), vertical stiffness (p = 0.004, d = 0.983). However, there was no significant difference in the jump height (p = 0.382, d = 0.267) and maximal isometric strength (p = 0.602, d = 0.147). Plyometric training provided improvements in reactive strength, vertical stiffness, but did not improve maximal isometric strength.