Active stiffness of the ankle in response to inertial and elastic loads
Active stiffness of the ankle in response to inertial and elastic loads
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DOI：
10.1016/j.jelekin.2004.03.005
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发表时间：
2004-10-01
影响因子：
2.5
通讯作者：
Gabriel, R
中科院分区：
文献类型：
--
作者：
Granata, KP;Wilson, SE;Gabriel, R
检查肌肉骨骼系统的有效刚度作为外部负载特征的函数。十三名健康受试者在中立踝关节姿势下主动收缩踝关节跖屈肌肉组织以支撑外部负载。肌肉骨骼刚度是根据背屈/跖屈扰动记录的动力学数据计算的。在支持 19 公斤和 38 公斤的外部负荷（有或没有拮抗共同收缩）时记录脚踝动力学。使用纯重力质量施加外部载荷。在单独的试验中，外部载荷通过与跖屈肌肉组织平行的钢弹簧拉伸施加，这也为系统提供了额外的平行刚度。令人惊讶的是，增加 4.9 和 8.1 kN/m 的外部刚度并没有显着改变脚踝加弹簧系统的刚度。这表明内在肌肉刚度和反射刚度的贡献随着外部刚度的增加而下降。这无法通过负载大小、踝关节姿势或共同激活来解释，因为惯性负载条件和弹性负载条件之间的这些相似。然而，非线性参数分析表明，平均固有刚度为 35.5 kN/m，反射增益为 11.6 kN/m，恒定反射延迟为 70 ms，准确地描述了经验结果。肌肉骨骼系统的机械动力学和延迟的神经运动反馈之间的相位响应相结合，提供对系统行为的稳健控制。 (C) 2004 Elsevier Ltd. 保留所有权利。
Effective stiffness of the musculoskeletal system was examined as a function of the characteristics of an external load. Thirteen healthy subjects provided active contraction of the ankle plantarflexion musculature in a neutral ankle posture to support an external load. Musculoskeletal stiffness was computed from kinetic data recorded in response to dorsiflexion/plantarflexion perturbations. Ankle dynamics were recorded while supporting external loads of 19 and 38 kg with and without antagonistic co-contraction. External loads were applied using pure gravitational mass. In separate trials external loads were applied from stretch of steel springs in parallel with the plantarflexion musculature that also provided added parallel stiffness to the system. Adding external stiffness of 4.9 and 8.1 kN/m surprisingly failed to significantly change the stiffness of the ankle-plus-spring system. This suggests contributions from intrinsic muscle stiffness and reflex stiffness declined in response to added external stiffness. This could not be explained by load magnitudes, ankle postures, or co-activation as these were similar between the inertial and elastic loading conditions. However, non-linear parametric analyses suggest mean intrinsic stiffness of 35.5 kN/m and reflex gain of 11.6 kN/m with a constant reflex delay of 70 ms accurately described the empirical results. The phase response between the mechanical dynamics of the musculoskeletal system and delayed neuromotor feedback combine to provide robust control of system behavior. (C) 2004 Elsevier Ltd. All rights reserved.