(56) COUNTERMOVEMENT VERTICAL JUMP FORCE-TIME CHARACTERISTICS FROM EIGHT NCAA DIVISION-I WOMEN’S COLLEGE VOLLEYBALL TEAMS

Purpose: The purpose of this study was to assess CMJ force-time metrics within a cohort of elite collegiate female volleyball athletes. Methods: Eighty-six resistance trained NCAA Division-I female volleyball athletes (height: 183.18 ± 9.81cm; weight: 77.58 ± 0.39) participated in this study. Following a standardized dynamic warm-up, athletes performed 2-4 CMJ on a dual force plate system (1000 Hz sampling rate). The vertical ground reaction force of each CMJ was recorded and the best performance was utilized for final analysis. A one-way analysis of variance was performed on all variables recorded by the dual force plate system and the Shapiro-Wilks test was also conducted to confirm normality. Results: Relative average braking force (p < 0.001), relative peak braking force (p =0.002), relative average propulsive force (p < 0.001), relative peak propulsive force (p < 0.001), relative average propulsive power (p = 0.042), relative peak propulsive power (p =0.034), relative average braking power (p < 0.001), relative peak braking power (p< 0.001), and time to takeoff (p < 0.001) significantly differed between position groups. Further differences were observed for measures of modified reactive strength index (p=0.002), braking phase duration (p < 0.001), propulsive phase duration (p < 0.001), countermovement depth (p < 0.001), and impulse ratio (p < 0.001) between position groups. However, no significant differences were observed for measures of jump height (p = 0.406), takeoff velocity (p = 0.415), or propulsive phase percentage (p =0.593). Conclusions: These findings highlight the position-specific similarities and differences of elite collegiate female volleyball athletes. While differences in CMJ kinematic variables differed between position groups, specifically, designated setter, outside hitter, and opposite hitters, no differences were observed in performance variables which further highlights the need for lower-body neuromuscular power development for athletes competing at the NCAA Division-I level. Practical Applications: To the authors’ knowledge, this is among the most recent analysis of this type specifically for NCAA Division-I female volleyball athletes. Furthermore, the collaboration between strength and conditioning professionals and sport scientists to support athlete health and performance contributed to the success of this project. These findings can be utilized to develop general and position-specific resistance training and practice approaches to enhance lower-body neuromuscular performance. From a resistance training perspective, the development of strength endurance, muscular strength, and power may contribute to enhanced on-court performance. From a practice perspective, implementing cardiovascular endurance-based drills that implement plyometric activities intermittently may also adequately prepare athletes for specific demands of competition. Acknowledgements: This research investigation was funded by the Clara Wu and Joseph Tsai Foundation.