Characterizing the quasi-stiffness and work of lower extremity joints is critical for evaluating human locomotion and designing assistive devices such as prostheses and orthoses intended to emulate the biological behavior of human legs. This work aims to establish statistical models that allow us to predict the ankle quasi-stiffness and net mechanical work for adults walking on level ground. During the stance phase of walking, the ankle joint propels the body through three distinctive phases of nearly constant stiffness known as the quasi-stiffness of each phase. Using a generic equation for the ankle moment obtained through an inverse dynamics analysis, we identify key independent parameters needed to predict ankle quasi-stiffness and propulsive work and also the functional form of each correlation. These parameters include gait speed, ankle excursion, and subject height and weight. Based on the identified form of the correlation and key variables, we applied linear regression on experimental walking data for 216 gait trials across 26 subjects (speeds from 0.75–2.63 m/s) to obtain statistical models of varying complexity. The most general forms of the statistical models include all the key parameters and have an R2 of 75% to 81% in the prediction of the ankle quasi-stiffnesses and propulsive work. The most specific models include only subject height and weight and could predict the ankle quasi-stiffnesses and work for optimal walking speed with average error of 13% to 30%. We discuss how these models provide a useful framework and foundation for designing subject- and gait-specific prosthetic and exoskeletal devices designed to emulate biological ankle function during level ground walking.
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机译：表征下肢关节的准刚度和功能对于评估人体运动和设计辅助设备（例如假肢和矫形器）以模拟人腿的生物学行为至关重要。这项工作旨在建立统计模型，使我们能够预测在水平地面上行走的成年人的踝关节准刚度和净机械功。在行走的站立阶段，脚踝关节将身体推进三个几乎恒定的刚度阶段，即每个阶段的准刚度。使用通过逆动力学分析获得的踝关节力矩的通用方程式，我们确定了预测踝关节准刚度和推进工作所需的关键独立参数，以及每个相关函数的功能形式。这些参数包括步态速度，脚踝偏移以及对象的身高和体重。基于相关性和关键变量的确定形式，我们对26个受试者（速度从0.75-2.63 m / s）的216个步态试验的实验步行数据进行了线性回归，以获得复杂度各异的统计模型。统计模型的最通用形式包括所有关键参数，并且在预测踝部准刚度和推进工作方面的R 2 为75％至81％。最具体的模型仅包括受试者的身高和体重，可以预测踝部准刚度，并以最佳步行速度工作，平均误差为13％至30％。我们讨论了这些模型如何为设计特定于对象和步态的假肢和骨骼外设备提供有用的框架和基础，这些假肢和骨骼设备旨在模拟水平地面行走过程中的生物踝关节功能。
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