Tosovic D, Than C, Brown J M M
Department of Anatomy and Developmental Biology, School of Biomedical Sciences, The University of Queensland, St. Lucia, 4072, Australia.
Eur J Appl Physiol. 2016 Aug;116(8):1485-94. doi: 10.1007/s00421-016-3398-7. Epub 2016 Jun 3.
Muscle fatigue has been identified as a risk factor for spontaneous muscle injuries in sport. However, few studies have investigated the accumulated effects of muscle fatigue on human muscle contractile properties. This study aimed to determine whether repeated bouts of exercise inducing acute fatigue leads to longer-term fatigue-related changes in muscle contractile properties.
Maximum voluntary contraction (MVC), electromyographic (EMG) and mechanomyographic (MMG) measures were recorded in the biceps brachii of 11 participants for 13 days, before and after a maximally fatiguing exercise protocol. The exercise protocol involved participants repetitively lifting a weight (concentric contractions only) equal to 40 % MVC, until failure.
A significant (p < 0.05) acute pre- to post-exercise decline of biceps brachii MVC and median power frequency (MPF) was observed each day, whilst no difference existed between pre-exercise MVC or MPF values on subsequent days (days 2-13). However, decreases in number of lift repetitions and in pre-exercise MMG values of muscle belly displacement, contraction velocity and half-relaxation velocity were observed through to day 13.
Whilst MVC and MPF measures resolved by the following day's test session, MMG measures indicated an ongoing decrement in muscle performance through days 2-13 consistent with the decline in lift repetitions observed. These results suggest that MMG may be more sensitive in detecting accumulated muscle fatigue than the 'gold standard' measures of MVC/MPF. Considering that muscle fatigue leads to injury, the on-going monitoring of MMG derived contractile properties of muscles in athletes may aid in the prediction of fatigued-induced muscle injury.
肌肉疲劳已被确认为运动中自发性肌肉损伤的一个风险因素。然而，很少有研究调查肌肉疲劳对人体肌肉收缩特性的累积影响。本研究旨在确定反复进行诱发急性疲劳的运动是否会导致肌肉收缩特性出现与长期疲劳相关的变化。
在一项极度疲劳的运动方案前后的13天里，记录了11名参与者肱二头肌的最大自主收缩（MVC）、肌电图（EMG）和机械肌电图（MMG）指标。运动方案要求参与者重复举起相当于40%MVC的重量（仅向心收缩），直至力竭。
每天均观察到肱二头肌MVC和中位功率频率（MPF）在运动前到运动后出现显著（p<0.05）的急性下降，而在随后几天（第2 - 13天）运动前的MVC或MPF值之间没有差异。然而，直到第13天，观察到举起重复次数以及肌肉腹位移、收缩速度和半松弛速度的运动前MMG值均有所下降。
虽然MVC和MPF指标在第二天的测试环节中恢复，但MMG指标表明在第2 - 13天肌肉性能持续下降，这与观察到的举起重复次数下降一致。这些结果表明，在检测累积的肌肉疲劳方面，MMG可能比MVC/MPF的“金标准”指标更敏感。鉴于肌肉疲劳会导致损伤，对运动员肌肉MMG衍生的收缩特性进行持续监测可能有助于预测疲劳诱导的肌肉损伤。
