Blangsted Anne Katrine, Sjøgaard Gisela, Madeleine Pascal, Olsen Henrik Baare, Søgaard Karen
Department of Physiology, National Institute of Occupational Health, Lersø Parkallé 105, DK-2100 Copenhagen, Denmark.
J Electromyogr Kinesiol. 2005 Apr;15(2):138-48. doi: 10.1016/j.jelekin.2004.10.004. Epub 2004 Dec 25.
Controversies exist regarding objective documentation of fatigue development with low-force contractions. We hypothesized that non-exhaustive, low-force muscle contraction may induce prolonged low-frequency fatigue (LFF) that in the subsequent recovery period is detectable by electromyography (EMG) and in particular mechanomyography (MMG) during low-force rather than high-force test contractions. Seven subjects performed static wrist extension at 10% maximal voluntary contraction (MVC) for 10 min (10%MVC10 min). Wrist force response to electrical stimulation of extensor carpi radialis muscle (ECR) quantified LFF. EMG and MMG were recorded from ECR during static test contractions at 5% and 80% MVC. Electrical stimulation, MVC, and test contractions were performed before 10%MVC10 min and at 10, 30, 90 and 150 min recovery. In spite of no changes in MVC, LFF persisted up to 150 min recovery but did not develop in a control experiment omitting 10%MVC10 min. In 5% MVC tests significant increase was found in time domain of EMG from 0.067+/-0.028 mV before 10%MVC10 min to 0.107+/-0.049 and 0.087+/-0.05 mV at 10 and 30 min recovery, respectively, and of the MMG from 0.054+/-0.039 ms(-2) to 0.133+/-0.104 and 0.127+/-0.099 ms(-2), respectively. No consistent changes were found in 80% MVC tests. In conclusion, non-exhaustive low-force muscle contraction resulted in prolonged LFF that in part was identified by the EMG and MMG signals.
关于低强度收缩时疲劳发展的客观记录存在争议。我们假设，非疲劳性的低强度肌肉收缩可能会诱发长时间的低频疲劳（LFF），在随后的恢复期，通过肌电图（EMG），尤其是在低强度而非高强度测试收缩期间的机械肌电图（MMG）可以检测到这种疲劳。七名受试者以最大自主收缩（MVC）的10%进行静态腕伸展10分钟（10%MVC10分钟）。通过对桡侧腕伸肌（ECR）进行电刺激后的腕部力量反应来量化LFF。在5%和80%MVC的静态测试收缩期间，从ECR记录EMG和MMG。在进行10%MVC10分钟之前以及恢复10、30、90和150分钟时进行电刺激、MVC和测试收缩。尽管MVC没有变化，但LFF在恢复150分钟时仍然存在，而在省略10%MVC10分钟的对照实验中并未出现。在5%MVC测试中，发现EMG时域从10%MVC10分钟之前的0.067±0.028 mV分别显著增加到恢复10分钟和30分钟时的0.107±0.049 mV和0.087±0.05 mV，MMG从0.054±0.039 ms⁻²分别增加到0.133±0.104 ms⁻²和0.127±0.099 ms⁻²。在80%MVC测试中未发现一致的变化。总之，非疲劳性低强度肌肉收缩导致了长时间的LFF，部分可通过EMG和MMG信号识别。
