Abstract
BACKGROUND: Drop height has previously been used as an effective programming parameter in plyometric jump training. Less is known about the usage of maximal rebound jump height from a distinct drop height as a parameter for individualized plyometric jump training. Hence, the aim of this study was to contrast the effects of two different drop jump (DJ) training modalities using either the individualized maximal rebound height (MRHT) or a standard (SDHT) drop height on selected measures of physical fitness in young volleyball players. METHODS: Thirty male young volleyball players aged 14 to 16 years were randomly assigned to an MRHT (n = 15) or an SDHT (n = 15) group. The MRHT group performed DJ exercises using a drop height according to the individual's maximal rebound jump height from 30 cm, 40 cm, and 50 cm drop heights. The SDHT group performed DJs following a standardized drop height (30 cm) across the 8-week intervention period. The overall training volume was similar between MRHT and SDHT with one to three sets of 8 to 10 repetitions of DJ exercises per session. Before and after training, jump height and the reactive strength index (RSI) were taken as dependent variables from 30, 40, and 50 cm drop heights. In addition, dynamic balance (Y-balance test) as well as linear sprint and change-of-direction (CoD) speed were assessed. RESULTS: Significant group × time interactions were found for jump height, balance, RSI, and linear sprint (p < 0.001; d = 0.12-3.42) but not CoD speed. Post hoc tests showed significant jump height improvements in favor of the MRHT group for drop heights from 30 cm (Δ20.4%, p < 0.001, d = 3.69), 40 cm (Δ20.3%, p < 0.001, d = 2.90), and 50 cm (Δ18.3%, p < 0.001, d = 3.37) and RSI50 (Δ30.14%, p < 0.001, d = 2.29). MRHT but not SDHT resulted in significant 5 m (Δ9.2%, p < 0.001, d = 1.32) and 20 m (Δ7.4%, p < 0.01, d = 2.30) linear sprint speed improvements. CONCLUSIONS: The findings demonstrate that MRHT but not SDHT improved DJ height, RSI, and linear sprint speed. Due to the importance of vertical jumps and short accelerations for overall competitive performance in volleyball, our results suggest that young male players should perform MRHT as part of plyometric jump training if the goal is to improve acceleration, reactive strength, and vertical jump performance.