Adaptation of center of mass control under microgravity in a whole-body lifting task
Adaptation of center of mass control under microgravity in a whole-body lifting task
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DOI：
10.1007/s002210050655
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发表时间：
1999-03-01
影响因子：
2
通讯作者：
Savelsbergh, GJP
中科院分区：
文献类型：
--
作者：
Kingma, I;Toussaint, HM;Savelsbergh, GJP
人体站立时的平衡通常被定义为保持重心（COM）在脚形成的支撑区域上的垂直投影。在微重力条件下，似乎不再需要控制平衡。然而，有几份报告表明，在手臂或腿抬起、脚尖站立或躯干弯曲等任务中，COM控制能力得到了保护。目前尚不清楚在短期暴露于微重力条件下，复杂的多关节运动是否也能保持COM控制。在目前的研究中，对在微重力条件下进行抛物线飞行的四名受试者的平衡控制动力学进行了研究。该研究的目的是审查在短期暴露于微重力条件下提升运动期间水平COM运动的轨迹是否发生变化，以及在几次提升运动之后是否有任何恢复的迹象。结果发现，与正常重力下的控制运动相比，在所有受试者的整个提升运动中，COM的水平位置向后移动。在微重力条件下的第二系列提升运动中，发现COM轨迹向正常重力情况的部分恢复，在微重力条件下，踝关节、膝关节、髋关节和腰关节的角度与正常重力条件下的角度有很大不同。在第二系列的提升运动中，关节角轨迹的恢复主要发生在那些可能有助于减少向后COM移位的角度。需要指出的是，微重力条件下的COM控制不是多余的，而是实用的。由于纯粹的机械原因，可能需要在微重力下持续进行COM控制，因为物体的旋转运动取决于COM位置相对于外力的适当控制。结果表明，从机械的角度来看，受试者可以受益于向后位移的COM在向下以及向上阶段的微重力下的提升运动。
Human balance in stance is usually defined as the preservation of the vertical projection of the center of mass (COM) on the support area formed by the feet. Under microgravity conditions, the control of equilibrium seems to be no longer required. However, several reports indicate preservation of COM control in tasks such as arm or leg raising, tiptoe standing, or trunk bending. It is still unclear whether COM control is also maintained in complex multijoint movements during short term exposure to microgravity. In the current study, the dynamics of equilibrium control were studied in four subjects performing two series of seven whole-body lifting movements under microgravity during parabolic flights. The aims of the study were to examine whether the trajectory of horizontal COM motion during lifting movements changes in short-term exposure to microgravity and whether there is any sign of recovery after several lifting movements. It was found that, compared with control movements under normal gravity, the horizontal position of the COM was shifted backward during the entire lifting movement in all subjects. In the second series of lifting movements under microgravity, a partial recovery of the COM trajectory toward the normal gravity situation was found. Under microgravity, angles of the ankle, knee, hip, and lumbar joints differed significantly from the angles found under normal gravity. Recovery of joint angular trajectories in the second series of lifting movements mainly occurred for those angles that could contribute to a reduction of the backward COM shift. It is to be pointed out that COM control under microgravity is not redundant but functional. Persisting COM control under microgravity may be required for pure mechanical reasons, since rotational movements of the body are dependent on adequate control of the COM position with respect to external forces. It is shown that, from a mechanical perspective, subjects can benefit from a backward displacement of the COM in the downward as well as the upward phase of the lifting movement under microgravity.