The study examined kinematic parameters and their inter- and intrasubject variability in the topspin forehand of seven top-level table tennis players. A wireless inertial measurement unit (IMU) system measured the movement of the playing hand to analyze the Ready position, Backswing, and Forward events, and a racket-mounted piezoelectric sensor captured the racket-ball Contact. In a four-phase cycle (Backswing, Hitting, Followthrough, and Back to Ready position), body sensors recorded the cycle and phase duration; angles in the sagittal plane at the shoulder, elbow, and wrist of the playing hand and at the knee joints; and acceleration of the playing hand at the moment of racket-ball contact. The coefficient of variation (CV) was calculated to determine the variability of kinematic parameters within and between players. The observed variability in stroke time duration was low () indicating constancy. The small-to-medium intraindividual variability of angles () indicates that each player used a broadly repeatable technique. The large intraindividual variability in movement was probably functional (i.e., motor adjustment and injury avoidance). Interindividual and intraindividual variability of knee and elbow angles was low; wrist extension was the most variable parameter () for all tasks, and shoulder joint variability was medium-to-large. Variability in hand acceleration was low (). Individual players achieved relatively constant hand acceleration at the moment of contact, possibly because angular changes at one joint (e.g., shoulder) could be compensated for by changes at another (e.g., wrist). These findings can help to guide the teaching-learning process and to individualize the training process.

中文翻译：

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使用可穿戴惯性传感器估算乒乓球上旋正手击球的运动学参数和可变性。

这项研究检查了七个顶级乒乓球运动员上旋正手的运动学参数及其对象间和对象内的变异性。无线惯性测量单元（IMU）系统测量了演奏手的运动，以分析“准备”位置，“后挥”和“前进”事件，而安装在球拍上的压电传感器捕获了“球拍接触”。在四个阶段的循环中（后摆，击中，跟踪和回到就绪位置），人体传感器记录了循环和阶段持续时间；演奏手的肩膀，肘部和手腕以及膝关节在矢状平面中的角度；和在球拍接触时演奏手的加速度。计算变异系数（CV）以确定运动员内部和运动员之间运动参数的变异性。）表示持续性。角度的中小内个体差异（）表示每个玩家都使用了广泛可重复的技术。运动中较大的个体差异可能是起作用的（即，运动调节和避免伤害）。膝和肘角度的个体间和个体内变异性较低；腕关节伸展是变化最大的参数（）的所有任务，而肩关节的变异程度则为中到大。手加速度的可变性低（）。单个玩家在接触时获得了相对恒定的手加速度，这可能是因为一个关节（例如，肩膀）处的角度变化可以通过另一关节（例如，腕部）的变化来补偿。这些发现有助于指导教学过程和个性化培训过程。