Yue G H, Bilodeau M, Hardy P A, Enoka R M
Department of Biomedical Engineering, Cleveland Clinic Foundation, OH 44195, USA.
Exp Physiol. 1997 May;82(3):567-92. doi: 10.1113/expphysiol.1997.sp004048.
Because short-term limb immobilization produces selective adaptations in the neuromuscular system that probably interact with the task-dependent expression of muscle fatigue, the purpose of this study was to determine the effects of limb immobilization on the ability of human subjects to sustain isometric contractions at low and moderate submaximal forces. Four weeks of elbow joint immobilization caused a substantial decrease in the daily activity of biceps brachii during immobilization, a significant reduction in the cross-sectional area and volume of the elbow flexor muscles as measured by magnetic resonance imaging, and a decline in the maximum voluntary contraction (MVC) activation and force of the elbow flexor muscles. Immobilization had a task-dependent effect on muscle fatigue with a substantially increased endurance time (reduced fatigability) at a low force (20% MVC) and no statistical effect at a moderate force (65% MVC). Despite atrophy of the elbow flexor muscles due to the immobilization, the twitch force elicited in biceps brachii by electrical stimulation was greater after immobilization. The selective improvement of fatigue resistance for the low-force contraction and the absence of a change in the time course of the twitch suggests that the immobilization-induced adaptations included an improved efficacy of some excitation-contraction processes and underscored the major role of these mechanisms in determining the endurance time for low-force, long-duration contractions.
由于短期肢体固定会在神经肌肉系统中产生选择性适应，这可能与任务依赖性的肌肉疲劳表现相互作用，因此本研究的目的是确定肢体固定对人类受试者在低强度和中等强度次最大力量下维持等长收缩能力的影响。四周的肘关节固定导致固定期间肱二头肌的日常活动大幅下降，通过磁共振成像测量，肘关节屈肌的横截面积和体积显著减小，肘关节屈肌的最大自主收缩（MVC）激活和力量下降。固定对肌肉疲劳有任务依赖性影响，在低力量（20%MVC）时耐力时间大幅增加（疲劳性降低），在中等力量（65%MVC）时无统计学影响。尽管由于固定导致肘关节屈肌萎缩，但固定后电刺激肱二头肌引发的抽搐力更大。低力量收缩的抗疲劳能力选择性提高以及抽搐时间进程无变化表明，固定诱导的适应包括一些兴奋 - 收缩过程的效率提高，并强调了这些机制在确定低力量、长时间收缩的耐力时间方面的主要作用。
