Oomen Nathalie M C W, Reeves N Peter, Priess M Cody, van Dieën Jaap H
MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands.
Department of Osteopathic Surgical Specialty, College of Osteopathic Medicine, Michigan State University, East Lansing, MI, USA; Michigan State University Center for Orthopedic Research, Lansing, MI, USA.
J Electromyogr Kinesiol. 2015 Oct;25(5):765-72. doi: 10.1016/j.jelekin.2015.07.001. Epub 2015 Jul 13.
When balancing, instability can occur when the object being balanced moves at a rate that is beyond the abilities of human motor control. This illustrates that responsiveness of motor control is limited and can be investigated by changing the dynamics of the task. In this study, the responsiveness of trunk motor control was investigated by changing the seat stiffness of an unstable seat. At decreasing levels of seat stiffness the probability of successfully balancing on the seat, speed of the seat, speed of the trunk relative to the seat (trunk-seat) and muscle activation of five trunk muscles were assessed. Also, across the different stiffness levels, the relation between trunk muscle activation and seat speed was determined. As hypothesized, with decreasing seat stiffness the probability of success decreased, seat speed and trunk-seat speed increased, and both agonist and antagonist activation increased. This shows that limits in the responsiveness of trunk motor control were reached during seated balancing. Furthermore, in line with our hypothesis, a positive relation was found between trunk muscle activation and seat speed. It appears that the central nervous system regulates trunk stiffness (via muscle coactivation) in relation to the dynamics of the task, possibly to maintain adequate responsiveness.
在平衡过程中，当被平衡物体的移动速度超出人类运动控制能力时，就会出现不稳定情况。这表明运动控制的反应能力是有限的，并且可以通过改变任务的动态特性来进行研究。在本研究中，通过改变不稳定座椅的座椅刚度来研究躯干运动控制的反应能力。在座椅刚度降低的情况下，评估了在座椅上成功保持平衡的概率、座椅速度、躯干相对于座椅的速度（躯干 - 座椅速度）以及五块躯干肌肉的肌肉激活情况。此外，在不同的刚度水平下，确定了躯干肌肉激活与座椅速度之间的关系。正如所假设的那样，随着座椅刚度的降低，成功概率降低，座椅速度和躯干 - 座椅速度增加，并且 agonist 和 antagonist 的激活都增加。这表明在坐姿平衡过程中达到了躯干运动控制反应能力的极限。此外，与我们的假设一致，在躯干肌肉激活与座椅速度之间发现了正相关关系。看来中枢神经系统会根据任务的动态特性调节躯干刚度（通过肌肉共同激活），可能是为了保持足够的反应能力。
