Laboratory CIAMS (Complexité, Innovation, Activités Motrices et Sportives), Team RIME (Risque, Intervention, Mouvement, Equilibre), UFR STAPS, University of Paris-Sud, 91440, Orsay Cedex, France.
Eur J Appl Physiol. 2010 Dec;110(6):1187-97. doi: 10.1007/s00421-010-1595-3. Epub 2010 Aug 18.
Voluntary arm movements are preceded by dynamical and electromyographical (EMG) phenomena in "postural segments" (i.e. body segments not directly involved in the voluntary movement) called "anticipatory postural adjustments" (APA). The present study examined how the central nervous system organizes APA under fatigued state of postural musculature elicited by series of high-level isometric contractions (HIC), i.e. corresponding to 60% of maximal voluntary contraction. Subjects (N = 14) purposely performed series of bilateral-forward reach task (BFR) under unipodal stance (dominant and non-dominant) before ("no fatigue" condition, NF) and after ("fatigue" condition, F) a procedure designed to obtain major fatigue in hamstrings. Centre-of-gravity acceleration, centre-of-pressure displacement, and electrical activity of trunk and leg muscles were recorded and quantified within a time-window typical of APA. Results showed that there was no significant effect of fatigue on the level of muscle excitation and APA onset in any of the postural muscles recorded. Similarly, no change in APA onset could be detected from the biomechanical traces. In contrast, results showed that the amplitude of anticipatory centre-of-pressure displacement and centre-of-gravity acceleration reached lower value in F than in NF. Similar results were obtained whether dominant or non-dominant leg was considered. The changes in biomechanical APA features could not be ascribed to a different focal movement performance (maximal BFR velocity and acceleration) between F and NF. These results suggest that, when fatigue is induced by HIC, the capacity of the central nervous system to adapt APA programming to the fatigued state of the postural muscle system might be altered.
自愿手臂运动之前会出现“姿势段”（即不直接参与主动运动的身体段）的动力和肌电图（EMG）现象，称为“预期姿势调整”（APA）。本研究考察了中枢神经系统如何在姿势肌肉的疲劳状态下组织 APA，这种疲劳状态是通过一系列高水平等长收缩（HIC）引起的，即相当于最大自主收缩的 60%。受试者（N=14）在单足站立（优势和非优势）下有意进行双侧前伸任务（BFR）系列，在此之前（“无疲劳”条件，NF）和之后（“疲劳”条件，F）进行一项旨在使腿筋产生主要疲劳的程序。在典型的 APA 时间窗口内记录和量化了重心加速度、压强中心位移以及躯干和腿部肌肉的电活动。结果表明，疲劳对记录的任何姿势肌肉的肌肉兴奋和 APA 起始水平均无显著影响。同样，从生物力学迹线也无法检测到 APA 起始的变化。相比之下，结果表明，与 NF 相比，F 时预期压强中心位移和重心加速度的振幅值较低。无论考虑优势腿还是非优势腿，均得到了相似的结果。生物力学 APA 特征的变化不能归因于 F 和 NF 之间不同的焦点运动表现（最大 BFR 速度和加速度）。这些结果表明，当 HIC 引起疲劳时，中枢神经系统适应姿势肌肉系统疲劳状态的 APA 编程能力可能会发生改变。
