Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan.
Department of Occupational Therapy, Kaohsiung Municipal Kai-Syuan Psychiatric Hospital, Kaohsiung 80276, Taiwan.
J Healthc Eng. 2021 Jun 11;2021:8884614. doi: 10.1155/2021/8884614. eCollection 2021.
By assuming that the human body rotates primarily around the ankle joint in the sagittal plane, the human body has been modelled as a single inverted pendulum (IP) to simulate the human quiet stance. Despite its popularity, the validity of the IP model has been challenged in many studies. Rather than testing the validity of the IP model as a true or false question, this work proposes a feature to quantify the degree of validity of the IP model. The development of the proposed feature is based on the fact that the IP model predicts that the horizontal acceleration of COM is proportional to the COP error which is defined as the difference between the center of pressure (COP) and the vertical projection of the center of mass (COM). Since the horizontal components of the acceleration of COM and the ground reaction force (GRF) are always proportional, the proposed feature is the correlation coefficient between the anterior-posterior (AP) components of GRF and the COP error. The efficacy of the proposed feature is demonstrated by comparing its differences for individuals in two age groups (18-24 and 65-73 years) in quiet standing. The experimental results show that the IP model is more suited for predicting the motion of the older group than the younger group. Our results also show that the proposed feature is more sensitive to aging effects than one of the most reliable and accurate COP-based postural stability features.
通过假设人体主要在矢状面内围绕踝关节旋转，人体被建模为单个倒立摆（IP）以模拟人体静止姿势。尽管该模型很受欢迎，但在许多研究中已经对其有效性提出了质疑。本研究不是将 IP 模型的有效性作为一个是与否的问题来测试，而是提出了一个特征来量化 IP 模型的有效性程度。所提出特征的开发基于以下事实，即 IP 模型预测 COM 的水平加速度与 COP 误差成正比，COP 误差定义为压力中心（COP）与质心（COM）的垂直投影之间的差异。由于 COM 的加速度和地面反作用力（GRF）的水平分量总是成正比，因此所提出的特征是 GRF 的前后（AP）分量与 COP 误差之间的相关系数。通过比较两个年龄组（18-24 岁和 65-73 岁）在安静站立时的个体的特征差异，验证了所提出特征的有效性。实验结果表明，IP 模型更适合于预测老年组的运动，而不是年轻组。我们的结果还表明，与最可靠和准确的基于 COP 的姿势稳定性特征之一相比，所提出的特征对老化效应更敏感。
