van Dieën Jaap H, Westebring-van der Putten Eleonora P, Kingma Idsart, de Looze Michiel P
Research Institute MOVE, Faculty of Human Movement Sciences, VU University Amsterdam, VanderBoechortstraat 9, NL-1081 BT Amsterdam, The Netherlands.
J Electromyogr Kinesiol. 2009 Jun;19(3):398-406. doi: 10.1016/j.jelekin.2007.11.010. Epub 2008 Feb 21.
This study was designed to determine whether trunk extensor fatigue occurs during low-level activity and whether this is associated with a drop in muscle tissue oxygenation. Electromyography (EMG) feedback was used to impose constant activity in a part of the trunk extensor muscles. We hypothesized that electromyographic manifestations of fatigue and decreased oxygenation would be observed at the feedback site and that EMG activity at other sites would be more variable without fatigue manifestations. Twelve volunteers performed 30-min contractions at 2% and 5% of the maximum EMG amplitude (EMGmax) at the feedback site. EMG was recorded from six sites over the lumbar extensor muscles and near-infrared spectroscopy was used to measure changes in oxygenation at the feedback site (left L3 level, 3 cm paravertebral). In both conditions, mean EMG activity was not significantly different between electrode sites, whereas the coefficient of variation was lower at the feedback site compared to other recording sites. The EMG mean power frequency (MPF) decreased consistently at the feedback site only. At 5% EMGmax, the decrease in MPF was significant at the group level at all sites ipsilateral to the feedback site. These results suggest that the limited variability of muscle activity at the EMG feedback site and at ipsilateral locations enhances fatigue development. No decreases in tissue oxygenation were detected. In conclusion, even at mean activity levels as low as 2% EMGmax, fatigue manifestations were found in the trunk extensors. These occurred in absence of changes in oxygenation of the muscle tissue.
本研究旨在确定在低强度活动期间躯干伸肌是否会出现疲劳，以及这是否与肌肉组织氧合下降有关。使用肌电图（EMG）反馈来使躯干伸肌的一部分保持恒定活动。我们假设在反馈部位会观察到疲劳的肌电图表现和氧合下降，并且其他部位的EMG活动会更具变异性而无疲劳表现。12名志愿者在反馈部位以最大EMG幅度（EMGmax）的2%和5%进行30分钟的收缩。从腰伸肌的六个部位记录EMG，并使用近红外光谱法测量反馈部位（左L3水平，椎旁3 cm）的氧合变化。在两种情况下，电极部位之间的平均EMG活动无显著差异，而反馈部位的变异系数低于其他记录部位。仅在反馈部位，EMG平均功率频率（MPF）持续下降。在5%EMGmax时，反馈部位同侧所有部位的MPF下降在组水平上具有显著性。这些结果表明，EMG反馈部位及同侧部位肌肉活动的有限变异性会促进疲劳的发展。未检测到组织氧合下降。总之，即使在低至2%EMGmax的平均活动水平下，躯干伸肌也会出现疲劳表现。这些疲劳表现在肌肉组织氧合无变化的情况下发生。
