Joint stiffness of the ankle and the knee in running
Joint stiffness of the ankle and the knee in running
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DOI：
10.1016/s0021-9290(02)00183-5
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发表时间：
2002-11-01
影响因子：
2.4
通讯作者：
Blickhan, R
中科院分区：
文献类型：
--
作者：
Günther, M;Blickhan, R
弹簧 - 质量模型是理解在重力作用下快速腿部运动整体动力学的有效基础。弹性这一基本概念，意味着腿部刚度是一个关键参数，在较低层次的运动控制中，即在肌肉反射和肌腱系统中也能发现。因此，整体腿部刚度由通过适当关节扭矩建立的局部弹性产生，这似乎是合理的。最近发表的一个弹性运作的分段式腿部模型预测，将关节弹性与腿部几何形状以及地面接触的初始条件进行适当调整，可确保腿部内部的稳定性。另一项近期研究表明，反过来，腿部的分段以及初始条件可能是新陈代谢和骨骼应力限制的结果。在本研究中，针对人类跑步时的初始条件和弹性关节特性，通过实验对理论预测进行了验证。测量了运动学和动力学数据，并通过逆动力学估算关节扭矩。通过参数拟合提取了描述所得关节特性的刚度和弹性非线性。我们的结果明确支持了理论预测：膝关节总是比踝关节更僵硬且伸展程度更大。此外，平均而言，膝关节扭矩特性表现出更高的非线性。根据文献，腿部几何形状是新陈代谢和材料应力限制的结果。适应于这种既定的几何形状，快速运动中的初始关节角度条件是新陈代谢和控制努力最小化之间的一种折衷。基于这种适应性，踝关节和膝关节之间适当的关节刚度比可被动地保障腿部内部的稳定性。所确定的关节非线性有助于腿部弹簧的线性化。（C）2002爱思唯尔科学有限公司。保留所有权利。
The spring-mass model is a valid fundament to understand global dynamics of fast legged locomotion under gravity. The underlying concept of elasticity, implying leg stiffness as a crucial parameter, is also found on lower motor control levels, i.e. in muscle-reflex and muscle-tendon systems. Therefore, it seems reasonable that global leg stiffness emerges from local elasticity established by appropriate joint torques. A recently published model of an elastically operating, segmented leg predicts that proper adjustment of joint elasticities to the leg geometry and initial conditions of ground contact provides internal leg stability. Another recent study suggests that in turn the leg segmentation and the initial conditions may be a consequence of metabolic and bone stress constraints. In this study, the theoretical predictions were verified experimentally with respect to initial conditions and elastic joint characteristics in human running. Kinematics and kinetics were measured and the joint torques were estimated by inverse dynamics. Stiffnesses and elastic nonlinearities describing the resulting joint characteristics were extracted from parameter fits. Our results clearly support the theoretical predictions: the knee joint is always stiffer and more extended than the ankle joint. Moreover, the knee torque characteristic on the average shows the higher nonlinearity. According to literature, the leg geometry is a consequence of metabolic and material stress limitations. Adapted to this given geometry, the initial joint angle conditions in fast locomotion are a compromise between metabolic and control effort minimisation. Based on this adaptation, an appropriate joint stiffness ratio between ankle and knee passively safeguards the internal leg stability. The identified joint nonlinearities contribute to the linearisation of the leg spring. (C) 2002 Elsevier Science Ltd. All rights reserved.