Strang Adam J, Berg William P
Department of Psychology, Miami University, 111 Psychology Building, Oxford, OH 45056, USA.
Exp Brain Res. 2007 Mar;178(1):49-61. doi: 10.1007/s00221-006-0710-5. Epub 2006 Oct 13.
To examine the fatigue-induced adaptive changes (e.g., timing) of anticipatory postural adjustments (APAs), APAs of 30 research participants were recorded before (baseline) and after (post-test) conditions of either rest (control group, n=15) or fatigue (fatigue group, n=15). Muscle fatigue was generated using a dead-lift exercise performed to exhaustion. Self-initiated postural perturbations were induced using a rapid unilateral arm-raising maneuver (focal movement), and APAs were obtained using electromyography (EMG) recorded bilaterally in the lumbar and thoracic paraspinal muscles as well as the hamstring muscles. Postural stability during the focal movement was assessed using a force plate. Results showed that fatigue had no effect on postural stability during the focal movement, and yet caused earlier APA onsets in three of the six muscles evaluated. In spite of early APA activation, the APA EMG integrals of two of the three postural control muscles which exhibited fatigue-induced early APA onsets (T9 and L4 contralateral paraspinals) did not differ between baseline and post-test measures. The findings suggest that early APA onset may enhance postural stability by permitting a longer duration APA which can counteract fatigue-induced decreases in the force-producing capability of muscles that contribute to postural stability.
为了研究疲劳诱导的预期姿势调整（APA）的适应性变化（如时间安排），在休息（对照组，n = 15）或疲劳（疲劳组，n = 15）这两种条件下，分别在30名研究参与者进行实验前（基线）和实验后（测试后）记录其APA。通过进行负重练习直至力竭来产生肌肉疲劳。使用快速单侧手臂上举动作（焦点动作）诱发自主姿势扰动，并通过双侧记录腰椎和胸椎旁脊柱肌肉以及绳肌的肌电图（EMG）来获取APA。使用测力板评估焦点动作期间的姿势稳定性。结果表明，疲劳对焦点动作期间的姿势稳定性没有影响，但在评估的六块肌肉中的三块中导致了APA起始时间提前。尽管APA提前激活，但在表现出疲劳诱导的APA起始时间提前的三块姿势控制肌肉中的两块（T9和L4对侧脊柱旁肌），其APA肌电图积分在基线和测试后测量之间没有差异。研究结果表明，APA起始时间提前可能通过允许更长持续时间的APA来增强姿势稳定性，该APA可以抵消疲劳引起的对姿势稳定性有贡献的肌肉力量产生能力的下降。
