Human Kinetics, Health Sciences, University of Ottawa, Ottawa, ON, Canada.
Exp Brain Res. 2012 Dec;223(4):553-62. doi: 10.1007/s00221-012-3282-6. Epub 2012 Oct 2.
The aim of this study was to determine whether and how young participants modulate their postural response to compensate for postural muscle fatigue during predictable but externally initiated continuous and oscillatory perturbations. Twelve participants performed ten postural trials before and after an ankle muscle fatigue protocol. Each postural trial was 1 min long and consisted of continuous backward and forward oscillations of the platform. Fatigue was induced by intermittent, bilateral isometric contractions of the ankle plantar- and dorsiflexors until the force production was reduced to 50 % of the pre-fatigue maximal voluntary contraction. Changes in the center of mass (COM) displacement, center of pressure (COP) displacement, and anterior-posterior location of the COP within the base of support were quantified as well as the activity of the tibialis anterior (TA), medial gastrocnemius (MG), quadriceps, and hamstring. All participants demonstrated postural stability post-fatigue by maintaining the displacement of their COM. Everyone also demonstrated a general forward shift in the anterior-posterior location of the COP within the base of support; however, two distinct postural modifications, corresponding to either an immediate fatigue-induced increase or decrease in the COP displacement during the backward platform translation, were recorded immediately post-fatigue. The changes in muscle onset latencies lasted beyond the recovery of the force production of the fatigued postural muscles. By 10 min post-fatigue, the participants showed a decrease in the COP displacement as well as an earlier activation of the postural muscles and an increased TA/MG co-activation relative to pre-fatigue. Although different strategies were used, the participants were able to adjust to and overcome postural muscle fatigue and remain balanced during the postural perturbations regardless of the direction of the platform movement. These adjustments lasted beyond the recovery of the ankle muscle force production indicating that they may be part of a centrally mediated protective response as opposed to a peripherally induced limitation to performance.
本研究旨在确定年轻参与者是否以及如何在可预测但外部引发的连续和振荡扰动期间，通过调节姿势反应来补偿姿势肌肉疲劳。12 名参与者在进行踝关节肌肉疲劳方案前后进行了 10 次姿势试验。每次姿势试验持续 1 分钟，包括平台的连续向后和向前振荡。通过间歇性、双侧等距收缩踝关节跖屈和背屈肌来诱导疲劳，直到力的产生降低到疲劳前最大自主收缩的 50%。还量化了质心（COM）位移、压力中心（COP）位移以及在支撑基础内 COP 的前后位置的变化，以及胫骨前肌（TA）、内侧腓肠肌（MG）、股四头肌和腘绳肌的活动。所有参与者在疲劳后都通过保持 COM 的位移来表现出姿势稳定性。每个人还表现出 COP 在支撑基础内前后位置的一般向前转移；然而，在疲劳后立即记录到两种不同的姿势修改，对应于向后平台平移过程中 COP 位移的即时疲劳诱导增加或减少。肌肉起始潜伏期的变化持续到疲劳后姿势肌肉的力产生恢复之外。在疲劳后 10 分钟，参与者表现出 COP 位移减少，姿势肌肉更早激活，以及 TA/MG 共同激活增加，与疲劳前相比。尽管使用了不同的策略，但参与者能够适应和克服姿势肌肉疲劳，并在姿势扰动期间保持平衡，无论平台运动的方向如何。这些调整持续到踝关节肌肉力产生的恢复之外，表明它们可能是中枢介导的保护反应的一部分，而不是对性能的外周限制。
