Functional Synergies Underlying Control of Upright Posture during Changes in Head Orientation
Functional Synergies Underlying Control of Upright Posture during Changes in Head Orientation
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DOI：
10.1371/journal.pone.0041583
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发表时间：
2012-08-01
期刊：
影响因子：
3.7
通讯作者：
Scholz, John P.
中科院分区：
文献类型：
--
作者：
Park, Eunse;Schoener, Gregor;Scholz, John P.
背景：对人类直立姿势的研究通常强调需要控制踝关节和髋关节以实现姿势稳定。然而，最近的研究表明，姿势稳定性涉及多自由度（DOF）的协调，特别是在执行超姿势任务时。本研究探讨了运动学的协同作用与控制的身体的位置在空间（二，四，六自由度模型）和头部的方向（六自由度模型）的变化。方法/主要调查结果：受试者要么跟踪一个垂直移动的目标与头戴式激光指针或固定在一个固定的点在4分钟的审判。在每个时间点的跟踪循环中进行不受控流形（UCM）分析，以确定与姿势稳定性或跟踪一致性相关的关节配置方差的结构。研究了模拟去除关节间协方差对该结构的影响，以进一步确定多关节协调的作用。结果表明，颈部关节的运动与其他关节的协调性差，以稳定的身体质心（CM）的位置。然而，颈部关节协调灵活的方式与更多的尾关节，以实现一致的变化，头部orientation.Conclusions/意义：多关节协调的理解需要参考的稳定性/控制的重要性能变量。该协调的性质因参考变量而异。直立姿势的稳定性主要涉及下肢和下躯干关节的多关节协调。然而，头部方向的一致变化需要这些关节与颈椎运动的灵活协调。一个两段模型的姿势控制是无法解释观察到的稳定性的CM位置在跟踪任务，进一步支持需要考虑多关节协调，以了解姿势的稳定性。
Background: Studies of human upright posture typically have stressed the need to control ankle and hip joints to achieve postural stability. Recent studies, however, suggest that postural stability involves multi degree-of-freedom (DOF) coordination, especially when performing supra-postural tasks. This study investigated kinematic synergies related to control of the body's position in space (two, four and six DOF models) and changes in the head's orientation (six DOF model).Methodology/Principal Findings: Subjects either tracked a vertically moving target with a head-mounted laser pointer or fixated a stationary point during 4-min trials. Uncontrolled manifold (UCM) analysis was performed across tracking cycles at each point in time to determine the structure of joint configuration variance related to postural stability or tracking consistency. The effect of simulated removal of covariance among joints on that structure was investigated to further determine the role of multijoint coordination. Results indicated that cervical joint motion was poorly coordinated with other joints to stabilize the position of the body center of mass (CM). However, cervical joints were coordinated in a flexible manner with more caudal joints to achieve consistent changes in head orientation.Conclusions/Significance: An understanding of multijoint coordination requires reference to the stability/control of important performance variables. The nature of that coordination differs depending on the reference variable. Stability of upright posture primarily involved multijoint coordination of lower extremity and lower trunk joints. Consistent changes in the orientation of the head, however, required flexible coordination of those joints with motion of the cervical spine. A two-segment model of postural control was unable to account for the observed stability of the CM position during the tracking task, further supporting the need to consider multijoint coordination to understand postural stability.