Ground reaction forces (GRFs) are essential for the analysis of human movement. To measure GRFs, 3D force plates that are fixed to the floor are used with large measuring ranges, excellent accuracy and high sample frequency. For less dynamic movements, like walking or squatting, portable 3D force plates are used, while if just the vertical component of the GRFs is of interest, pressure plates or in-shoe pressure measurements are often preferred. In many cases, however, it is impossible to measure 3D GRFs, e.g., during athletic competitions, at work or everyday life. It is still challenging to predict the horizontal components of the GRFs from kinematics using biomechanical models. The virtual pivot point (VPP) concept states that measured GRFs during walking intercept in a point located above the center of mass, while during running, the GRFs cross each other at a point below the center of mass. In the present study, this concept is used to compare predicted GRFs from measured kinematics with measured 3D-GRFs, not only during walking but also during more static movements like squatting and inline lunge. To predict the GRFs a full-body biomechanical model was used while gradually changing the positions of the VPP. It is shown that an optimal VPP improves the prediction of GRFs not only for walking but also for inline lunge and squats.

中文翻译：

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虚拟枢轴点概念改进了地面反作用力的预测

地面反作用力 (GRF) 对于分析人体运动至关重要。为了测量 GRF，使用固定在地板上的 3D 测力台，具有大测量范围、出色的精度和高采样频率。对于动态较小的运动，如步行或蹲下，可使用便携式 3D 测力台，而如果仅对 GRF 的垂直分量感兴趣，则通常首选压力板或鞋内压力测量。然而，在许多情况下，无法测量 3D GRF，例如在体育比赛、工作或日常生活中。使用生物力学模型从运动学预测 GRF 的水平分量仍然具有挑战性。虚拟枢轴点 (VPP) 概念指出，在步行期间在位于质心上方的点拦截时测量 GRF，而在跑步期间，GRF 在质心下方的点处相互交叉。在本研究中，这个概念用于将测量的运动学预测的 GRF 与测量的 3D-GRF 进行比较，不仅在步行期间，而且在蹲和内联弓步等更多静态运动期间。为了预测 GRF，使用了全身生物力学模型，同时逐渐改变 VPP 的位置。结果表明，最佳 VPP 不仅可以改善步行的 GRF 预测，还可以改善直列弓步和深蹲的 GRF 预测。