(67) BRIDGING THE GAP: NORMATIVE COUNTERMOVEMENT VERTICAL JUMP FORCE-TIME CHARACTERISTICS FROM EIGHT NCAA DIVISION-I WOMEN’S COLLEGE VOLLEYBALL TEAMS

Purpose: The primary purpose of this study was to provide normative reference values for specific CMJ force-time characteristics of interest. A secondary purpose was to develop and examine a novel method for evaluating stretch shortening cycle (SSC) efficiency during the CMJ. Methods: Eighty-six resistance trained NCAA Division-I female volleyball athletes (height: 183.18 ± 9.81cm; weight: 77.58 ± 0.39kg) from eight teams 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 analyses. Percentile rank values for CMJ force-time metrics of interest were calculated for the sample and later categorized by position group (i.e., defensive specialist, libero, middle blocker, etc.) and performance category (i.e., elite – 100-80%; good – 75-55%; average – 50%; below average – 45-30%; poor – 25-5%). Novel ratios were developed which accounted for braking and propulsive force and power. Results: Normative CMJ force-time metrics of interest for athletes categorized as “elite” were as follows; jump height=45.75 cm – 36.27 cm; relative average propulsive power=39.87–31.47 W/kg; relative average braking power=-18.86 - -16.57 W/kg; relative average propulsive force=270.18–217.08 N/kg; relative average braking force=161.83–179.24 N/kg; time to takeoff=0.53–0.67 seconds; braking phase duration=0.11–0.13 seconds; propulsive phase duration=0.19–0.24 seconds; modified reactive strength index=0.85–0.52; and impulse ratio=3.65–2.53. Dynamic average and peak relative force and power ratios did not correlate significantly with jump height (r=-0.143-0.142; p=0.249 – 0.253) but did however correlate strongly with impulse ratio (r=0-0.910-0.846; p=< 0.001) which has been reported to be a criterion measure of transference of force via the SSC. Conclusions: Based on the observations of this investigation, normative values for elite, good, average, below average, and poor performers during the CMJ assessment were identified. Furthermore, a novel ratio for evaluating the efficiency of the SSC was developed that could enhance approaches for athlete monitoring and development. Practical Applications: To the authors’ knowledge, this is among the first published analysis 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. Altogether, these findings can be utilized to enhance athletic development, progression, and performance through resistance training approaches and monitoring of neuromuscular fatigue with normative values as a reference. Acknowledgements: This research investigation was funded by the Clara Wu and Joseph Tsai Foundation.