Gueguen N, Coyle T, Craig C, Bootsma R, Mouchnino L
Laboratoire Mouvement et Perception, Faculté des Sciences du Sport, CNRS-Université de la Méditerranée, 163 avenue de Luminy, 13288 Marseille cedex 9, France.
Exp Brain Res. 2004 Jun;156(4):471-7. doi: 10.1007/s00221-003-1808-7. Epub 2004 Feb 14.
During lateral leg raising, a synergistic inclination of the supporting leg and trunk in the opposite direction to the leg movement is performed in order to preserve equilibrium. As first hypothesized by Pagano and Turvey (J Exp Psychol Hum Percept Perform, 1995, 21:1070-1087), the perception of limb orientation could be based on the orientation of the limb's inertia tensor. The purpose of this study was thus to explore whether the final upper body orientation (trunk inclination relative to vertical) depends on changes in the trunk inertia tensor. We imposed a loading condition, with total mass of 4 kg added to the subject's trunk in either a symmetrical or asymmetrical configuration. This changed the orientation of the trunk inertia tensor while keeping the total trunk mass constant. In order to separate any effects of the inertia tensor from the effects of gravitational torque, the experiment was carried out in normo- and microgravity. The results indicated that in normogravity the same final upper body orientation was maintained irrespective of the loading condition. In microgravity, regardless of loading conditions the same (but different from the normogravity) orientation of the upper body was achieved through different joint organizations: two joints (the hip and ankle joints of the supporting leg) in the asymmetrical loading condition, and one (hip) in the symmetrical loading condition. In order to determine whether the different orientations of the inertia tensor were perceived during the movement, the interjoint coordination was quantified by performing a principal components analysis (PCA) on the supporting and moving hips and on the supporting ankle joints. It was expected that different loading conditions would modify the principal component of the PCA. In normogravity, asymmetrical loading decreased the coupling between joints, while in microgravity a strong coupling was preserved whatever the loading condition. It was concluded that the trunk inertia tensor did not play a role during the lateral leg raising task because in spite of the absence of gravitational torque the final upper body orientation and the interjoint coupling were not influenced.
在侧抬腿过程中，支撑腿和躯干会向与腿部运动相反的方向协同倾斜，以保持平衡。正如Pagano和Turvey最初所假设的那样（《实验心理学杂志：人类感知与表现》，1995年，21卷：1070 - 1087页），肢体方位的感知可能基于肢体惯性张量的方位。因此，本研究的目的是探讨最终上身方位（躯干相对于垂直方向的倾斜度）是否取决于躯干惯性张量的变化。我们施加了一种负载条件，在受试者的躯干上以对称或不对称配置添加了总质量为4千克的负载。这改变了躯干惯性张量的方位，同时保持躯干总质量不变。为了将惯性张量的任何影响与重力矩的影响区分开来，实验在正常重力和微重力条件下进行。结果表明，在正常重力下，无论负载条件如何，最终上身方位都保持不变。在微重力环境中，无论负载条件如何，上身都通过不同的关节组合达到相同（但与正常重力下不同）的方位：在不对称负载条件下为两个关节（支撑腿的髋关节和踝关节），在对称负载条件下为一个关节（髋关节）。为了确定在运动过程中是否能感知到惯性张量的不同方位，通过对支撑和运动的髋关节以及支撑踝关节进行主成分分析（PCA）来量化关节间的协调性。预计不同的负载条件会改变PCA的主成分。在正常重力下，不对称负载会降低关节之间的耦合，而在微重力环境中，无论负载条件如何，都会保持较强的耦合。得出的结论是，在侧抬腿任务中躯干惯性张量不起作用，因为尽管没有重力矩，但最终上身方位和关节间耦合并未受到影响。
