Postural sway is a product of the neuromuscular system that is commonly used in contemporary labs and clinics for the assessment of postural stability. In this study, we analyzed the transient responses of the neuromuscular system during the rise-on-toes (ROT) movement in eighteen 11 yrs old girls. Their center of pressure (COP) trajectories were recorded with standard force-platform during the transition from quiet stance to standing on toes. To assess the robustness of children's postural stability, we compared the ROT trajectories while the movement was performed with and without vision. Our results confirmed that the dynamic characteristics of the COP step response were significantly modified by visual feedback. In particular, the ROT test performed with eyes closed (EC) was characterized by a four-fold increase of COP chaotic oscillations at the target (tiptoe) position. This resulted in a substantial increase in the movement's index of difficulty (ID) thus to achieve adequate accuracy of the target-oriented movement the COP velocity was decreased accordingly. This inherent strategy of the brain controller allowed for precise positioning of the COP within the reduced size of the target. In conclusion, the dynamics of the ROT movement is always precisely adjusted to the stability of the upright posture, and thus, the dynamic characteristics of the COP step response are also sensitive measures of postural stability and the ROT can be recommended as a useful test for this assessment in the general population.

中文翻译：

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人体运动系统的阶跃响应作为儿童姿势稳定性的衡量标准


姿势摇摆是神经肌肉系统的产物，在当代实验室和诊所中通常用于评估姿势稳定性。在这项研究中，我们分析了 18 名 11 岁女孩在踮起脚尖 (ROT) 运动期间神经肌肉系统的瞬时反应。在从安静姿势到踮起脚尖站立的过程中，用标准力平台记录了他们的压力中心（COP）轨迹。为了评估儿童姿势稳定性的稳健性，我们比较了在有视力和无视力的情况下进行运动时的 ROT 轨迹。我们的结果证实，视觉反馈显着改变了 COP 阶跃响应的动态特性。特别是，闭眼（EC）进行的 ROT 测试的特点是目标（脚尖）位置 COP 混沌振荡增加了四倍。这导致运动难度指数 (ID) 大幅增加，因此为了实现目标导向运动的足够精度，COP 速度相应降低。大脑控制器的这种固有策略允许在缩小的目标尺寸内精确定位 COP。总之，ROT 运动的动态总是精确地调整为直立姿势的稳定性，因此，COP 阶跃响应的动态特性也是姿势稳定性的敏感度量，并且 ROT 可以推荐作为直立姿势的有用测试。对一般人群的这一评估。