The application of force is a key aspect of performance during athletic activities. In jumping, the timing and magnitude of force application are important performance factors. The relative timing of forces has only been investigated in the countermovement jump. This study aimed to explore if the synchronization of peak concentric force with the instance of zero velocity during a drop jump impacted performance and examine the relationship of force–time curve shape to performance. Sixty‐six state‐level athletes (24 males and 42 females) completed drop jumps from a 30 cm box onto dual force plates. The jump with the highest reactive strength index (RSI) score was taken for analysis and classified as synchronous or asynchronous based on the relative timing of peak concentric force and zero velocity. RSI and other force–time variables were compared between groups, and functional principal component analysis (fPCA) was performed on the force–time curves, which were used to perform functional principal component regression (fPCR). Synchronous jumpers exhibited greater RSI scores and shorter contact times compared to asynchronous jumpers. Performance differences were largely driven by improved concentric kinetics, which the fPCR model revealed to have the greatest influence on RSI. Sex was also found to be a significant factor for RSI in the fPCR model. fPCA revealed that greater force application preceding and throughout the amortization phase was positively associated with RSI. The timing of peak concentric force and the shape of the force–time curve are key factors for drop jump performance, and these concepts should be investigated further in other athletic activities.

中文翻译：

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探索 Drop Jump 中的峰值同心力和零速度同步


力量的应用是体育活动中表现的一个关键方面。在跳跃中，施加力的时间和大小是重要的性能因素。力的相对时间仅在反向运动跳跃中进行了研究。本研究旨在探讨在跌落跳跃期间峰值同心力与零速度实例的同步是否会影响性能，并检查力-时间曲线形状与性能的关系。66 名州级运动员（24 名男性和 42 名女性）完成了从 30 厘米盒子到双测力板上的跳落。对反应强度指数 （RSI） 得分最高的跳跃进行分析，并根据峰值同心力和零速度的相对时间分为同步或异步。比较组间 RSI 和其他力 - 时间变量，并在力 - 时间曲线上进行功能主成分分析 （fPCA），用于进行功能主成分回归 （fPCR）。与异步跳线相比，同步跳线表现出更高的 RSI 分数和更短的接触时间。性能差异主要是由同心动力学的改善驱动的，fPCR 模型显示同心动力学对 RSI 的影响最大。在 fPCR 模型中，性别也被发现是 RSI 的一个重要因素。fPCA 显示，在摊销阶段之前和整个摊销阶段施加更大的力与 RSI 呈正相关。峰值同心力的时间和力-时间曲线的形状是下落跳跃表现的关键因素，这些概念应在其他体育活动中进一步研究。