Concentric Rate of Force Development, Squat Strength, and Faster Unloading Associated With Change-of-Direction Performance and Its Deficit in Female Volleyball Players

Purpose : Athletes who perform faster changes of direction (CODs) often exhibit superior leg strength, jumping performance, and linear sprint performance. However, these abilities only partially correlate with COD deficit (CODD), and relying solely on correlation analysis may lead to misinterpretations due to unaddressed, additive, or confounding effects. This study investigated the association between COD/CODD performance and various jump heights, countermovement-jump (CMJ) phase-specific performance, leg strength, and linear sprint performance. Multiple linear-regression models with stepwise selection were used to explore and adjust the additive effects and confounders of these factors. Methods: Eighteen female intercollegiate volleyball athletes performed 10- and 20-m linear sprints and proagility tests, and their CODD and physical performance metrics were measured. Furthermore, squat jump and CMJ height, back-squat 1-repetition maximum (BS1RM) corrected for body mass (relative), and CMJ phase-specific performance, including vertical force and rate of force development during eccentric unloading, yielding, braking, and concentric phases, were measured. Results: Concentric-phase rate of force development at 100 milliseconds, relative BS1RM, and squat-jump height were retained in the 10-m COD model (adjusted R 2 = .515, P = .004). The absolute BS1RM and minimum power at the unloading phase of CMJ were retained in the 10-m CODD model (adjusted R 2 = .746, P < .001). In contrast, no variables were retained in the 20-m COD model. Conclusions: The results suggest that enhancement of overall leg-contraction power and strength and rapid concentric force production immediately after eccentric braking may enhance 10-m COD/CODD performance in volleyball players.