Ankle and hip postural strategies defined by joint torques
Ankle and hip postural strategies defined by joint torques
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DOI：
10.1016/s0966-6362(99)00032-6
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发表时间：
1999-10-01
期刊：
影响因子：
2.4
通讯作者：
Zajac, FE
中科院分区：
文献类型：
--
作者：
Runge, CF;Shupert, CL;Zajac, FE
以前的研究已经确定了两个离散的策略，用于控制姿势在矢状面的基础上的EMG激活：身体运动学。地面反作用力。踝关节策略的特点是身体摇摆类似于一个单段倒立摆，并引起了平坦的支持表面。相反。髋关节策略的特征在于类似于在髋关节处分开的双段倒立摆的身体摇摆和在短的或柔顺的支撑表面上引起的UAS。然而，生物力学优化模型表明，髋关节策略也应该被观察到响应于在平坦表面上的快速平移，只要脚被约束为保持与地板接触并且膝盖被约束为保持笔直。本研究的目的是检查髋关节策略的实验证据，在姿势反应向后平移的平面支撑表面，并确定是否分析关节扭矩将提供证据，两个独立的姿势策略。正常受试者站在一个平坦的支持表面上向后平移的速度范围从快（55厘米/秒）到慢（5厘米/秒）。肌电图激活和关节运动学显示模式的变化与以前的实验描述的混合髋关节和踝关节的策略，随着平台速度的增加。关节扭矩分析显示，在快速平移过程中，踝跖屈肌扭矩增加了髋屈肌扭矩。这一发现表明，除了髋关节的战略，踝关节的战略，以产生一个连续的姿势反应。没有观察到髋关节扭矩不伴随踝关节扭矩（纯髋关节策略）。虽然姿势控制策略以前已被定义的身体如何移动，我们得出结论，关节力矩，这表明身体运动是如何产生的，是有用的，在定义姿势控制策略。这些结果也说明了身体的生物力学如何将离散的控制模式转化为连续的姿势矫正。(C)1999 Elsevier Science B. V.保留所有权利。
Previous studies have identified two discrete strategies for the control of posture in the sagittal plane based on EMG activations: body kinematics. and ground reaction forces. The ankle strategy was characterized by body sway resembling a single-segment-inverted pendulum and was elicited on flat support surfaces. In contrast. the hip strategy was characterized by body sway resembling a double-segment inverted pendulum divided at the hip and uas elicited on short or compliant support surfaces. However, biomechanical optimization models have suggested that hip strategy should be observed in response to fast translations on a flat surface also, provided the feet are constrained to remain in contact with the floor and the knee is constrained to remain straight. The purpose of this study was to examine the experimental evidence for hip strategy in postural responses to backward translations of a flat support surface and to determine whether analyses of joint torques would provide evidence for two separate postural strategies. Normal subjects standing on a flat support surface were translated backward with a range of velocities from fast (55 cm/s) to slow (5 cm/s). EMG activations and joint kinematics showed pattern changes consistent with previous experimental descriptions of mixed hip and ankle strategy with increasing platform velocity. Joint torque analyses revealed the addition of a hip flexor torque to the ankle plantarflexor torque during fast translations. This finding indicates the addition of hip strategy to ankle strategy to produce a continuum of postural responses. Hip torque without accompanying ankle torque (pure hip strategy) was not observed. Although postural control strategies have previously been defined by how the body moves; we conclude that joint torques, which indicate how body movements are produced, are useful in defining postural control strategies. These results also illustrate how the biomechanics of the body can transform discrete control patterns into a continuum of postural corrections. (C) 1999 Elsevier Science B.V. All rights reserved.