Kipp Kristof, Kiely Michael T, Geiser Christopher F
Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin.
J Strength Cond Res. 2016 May;30(5):1341-7. doi: 10.1519/JSC.0000000000001226.
The purpose of this study was to investigate the validity of the reactive strength index modified (RSImod) as a measure of lower body explosiveness. Fifteen female, National Collegiate Athletic Association Division I volleyball players performed vertical countermovement jumps (CMJs) while standing on a force plate. Each player performed 3 CMJs. The vertical ground reaction forces collected during each jump were used to calculate jump height, time to take-off, time to peak force, peak force, peak rate of force development, and peak power; the latter 3 variables were all normalized to body mass. Reactive strength index modified was calculated as the ratio between jump height and time to take-off. All variables, except for jump height, were then entered a factor analysis, which reduced the input data into 2 factors: a force factor and a speed factor. Although RSImod loaded more strongly onto the force factor, further analysis showed that RSImod loaded positively onto both force and speed factors. Visual analysis of the Cartesian coordinates also showed that RSImod loaded into the quadrant of greater force and speed abilities. These results indicate that the construct of RSImod, as derived from CMJ force-time data, captures a combination of speed-force factors that can be interpreted as lower body explosiveness during the CMJ. Reactive strength index modified therefore seems to be a valid measure to study lower body explosiveness.
本研究的目的是调查改良反应力量指数（RSImod）作为衡量下肢爆发力指标的有效性。15名美国国家大学体育协会第一分区的女子排球运动员站在测力板上进行垂直反向跳（CMJ）。每名运动员进行3次CMJ。每次跳跃过程中收集的垂直地面反作用力用于计算跳跃高度、起跳时间、达到峰值力的时间、峰值力、峰值力发展速率和峰值功率；后3个变量均按体重进行了标准化。改良反应力量指数的计算方法是跳跃高度与起跳时间之比。然后，除跳跃高度外的所有变量都进入了因子分析，该分析将输入数据简化为两个因子：力量因子和速度因子。尽管RSImod在力量因子上的载荷更强，但进一步分析表明，RSImod在力量因子和速度因子上均呈正向载荷。对笛卡尔坐标的可视化分析也表明，RSImod位于力量和速度能力更强的象限。这些结果表明，从CMJ力量-时间数据得出的RSImod结构捕捉到了速度-力量因子的组合，这可以解释为CMJ过程中的下肢爆发力。因此，改良反应力量指数似乎是研究下肢爆发力的有效指标。
