Huang Chien-Ting, Huang Chien-Chun, Young Ming-Shing, Hwang Ing-Shiou
Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan.
Eur J Appl Physiol. 2007 Aug;100(6):675-83. doi: 10.1007/s00421-007-0460-5. Epub 2007 Apr 18.
In reference to electromyographic measurement, the study was conducted to reassess differences in the behavior of fatigue-related neuromuscular function between young and elderly humans with limb acceleration (LA). Fourteen young and fourteen elderly subjects performed sustained index abduction at 75% of their maximal voluntary contractions (MVC) until task failure. Measures of neuromuscular function, including temporal/spectral features of muscle activity of the first dorsal interosseous (FDI) and LA of the index and hand, were monitored. The results showed a manifest fatigue-induced increase in LA of the index in the elderly group, but not in the young group. In contrast, only the young group developed a significant increase in amplitude of the electromyography (EMG) until task failure. Spectral analyses of LA in the index reflected marked age-dependent reorganization following muscle fatigue, with a greater reduction of relative spectral amplitude of LA in the range of 20-40 Hz, but a lesser reduction in coherence between EMG and LA in the elderly group. In line with fatigue-associated restructuring of LA, the mechanical coupling of the metacarpophalangeal joint was more severely undermined in the elderly group than in the young group. The present study manifested an age-related difference in the relative contributions of neural versus mechanical factors to muscle fatigue. Subsequent to a high-level sustained submaximal isometric contraction, a predominant mechanical failure of the musculotendon complex in the elderly was featured with LA, whereas EMG measurement characterized prevailing impairment of neuromuscular propagation in the young.
关于肌电图测量，本研究旨在通过肢体加速度（LA）重新评估年轻人和老年人之间与疲劳相关的神经肌肉功能行为差异。14名年轻受试者和14名老年受试者以其最大自主收缩（MVC）的75%进行持续的示指外展，直至任务失败。监测神经肌肉功能指标，包括第一背侧骨间肌（FDI）的肌肉活动的时间/频谱特征以及示指和手部的LA。结果显示，老年组示指的LA出现明显的疲劳诱导增加，而年轻组未出现。相反，只有年轻组在任务失败前肌电图（EMG）幅度出现显著增加。示指LA的频谱分析反映了肌肉疲劳后明显的年龄依赖性重组，在20 - 40 Hz范围内，老年组LA的相对频谱幅度降低更大，但EMG与LA之间的相干性降低较小。与LA的疲劳相关重组一致，老年组掌指关节的机械耦合比年轻组受到更严重的破坏。本研究表明，在肌肉疲劳中，神经因素与机械因素的相对贡献存在年龄相关差异。在高水平持续次最大等长收缩后，老年人肌肉肌腱复合体的主要机械故障表现为LA，而年轻组的EMG测量则显示神经肌肉传导普遍受损。
