Adaptation of multijoint coordination during standing balance in healthy young and healthy old individuals
Adaptation of multijoint coordination during standing balance in healthy young and healthy old individuals
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DOI：
10.1152/jn.00030.2015
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发表时间：
2016-03-01
影响因子：
2.5
通讯作者：
van der Kooij, H.
中科院分区：
文献类型：
--
作者：
Engelhart, D.;Pasma, J. H.;van der Kooij, H.
站立平衡需要脚踝和臀部之间的多关节协调。我们研究了人类如何调整他们的多关节协调来适应各种条件，以及健康的年轻参与者和健康的老年人之间的适应是否不同。推/拉杆干扰平衡，在髋关节水平和肩胛骨之间施加两个连续和独立的力干扰。此外，施加外部力场，以髋部的外部刚度为代表，稳定或破坏参与者的平衡。多变量闭环系统识别技术用于描述神经肌肉控制机制，通过量化校正关节扭矩作为对身体摇摆的响应，以频率响应函数（frf）表示。对frf的模型拟合导致对踝关节和髋关节的时间延迟、固有刚度、自反刚度和自反阻尼的估计。与年轻参与者相比，老年人产生了相似的矫正关节扭矩，但身体摆动减少，与年龄增加的FRF幅度相对应。当髋部施加稳定或不稳定的外力时，年轻和老年参与者都通过降低或分别增加脚踝周围的神经肌肉控制动作来适应多关节协调，表现为FRF大小的变化。然而，与年轻参与者相比，老年人的适应能力较差。对frf的模型拟合显示，老年人踝关节的固有刚度和反射性刚度更高，髋关节的时间延迟也更高。此外，与年轻参与者相比，老年人对踝关节周围反射性僵硬的适应程度更低。这些结果表明，老年人身体僵硬，适应外力的能力较差。
Standing balance requires multijoint coordination between the ankles and hips. We investigated how humans adapt their multijoint coordination to adjust to various conditions and whether the adaptation differed between healthy young participants and healthy elderly. Balance was disturbed by push/pull rods, applying two continuous and independent force disturbances at the level of the hip and between the shoulder blades. In addition, external force fields were applied, represented by an external stiffness at the hip, either stabilizing or destabilizing the participants' balance. Multivariate closed-loop system-identification techniques were used to describe the neuromuscular control mechanisms by quantifying the corrective joint torques as a response to body sway, represented by frequency response functions (FRFs). Model fits on the FRFs resulted in an estimation of time delays, intrinsic stiffness, reflexive stiffness, and reflexive damping of both the ankle and hip joint. The elderly generated similar corrective joint torques but had reduced body sway compared with the young participants, corresponding to the increased FRF magnitude with age. When a stabilizing or destabilizing external force field was applied at the hip, both young and elderly participants adapted their multijoint coordination by lowering or respectively increasing their neuromuscular control actions around the ankles, expressed in a change of FRF magnitude. However, the elderly adapted less compared with the young participants. Model fits on the FRFs showed that elderly had higher intrinsic and reflexive stiffness of the ankle, together with higher time delays of the hip. Furthermore, the elderly adapted their reflexive stiffness around the ankle joint less compared with young participants. These results imply that elderly were stiffer and were less able to adapt to external force fields.