Sensitivity of 24-h EMG duration and intensity in the human vastus lateralis muscle to threshold changes
Sensitivity of 24-h EMG duration and intensity in the human vastus lateralis muscle to threshold changes
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DOI：
10.1152/japplphysiol.00757.2009
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发表时间：
2010-03-01
影响因子：
3.3
通讯作者：
Thomas, Christine K.
中科院分区：
文献类型：
--
作者：
Klein, Cliff S.;Peterson, Lillian B.;Thomas, Christine K.
克莱因CS，彼得森LB，费雷尔·S，托马斯·CK。人股外侧肌24小时肌电持续时间和强度对阈值变化的敏感性。应用生理学杂志108：655-661,2010。2009年12月10日首次出版；doi：10.1152/japplPhysiol。00757.2009.-很少有研究使用肌电信号(EMG)来量化24小时内的下肢肌肉活动。没有人描述了用不同的阈值分析数据时肌电持续时间和强度的变化。对10例20~48岁受试者股外侧肌(VL)进行24 h双侧肌电连续记录，记录记录前后股四头肌力、最大自主收缩(MVC)25%、50%、75%、100%的VL肌电、自主激活百分比(Twitch插值法)和复合动作电位(M波)。离线后，将24小时肌电积分(IEMG，10ms时间常数)归一化为MVC IEMG。当以基线(+3SD)为阈值进行分析时，总肌电持续时间和平均IEMG分别为1~3h和3.2~12.1%MVC。当以更高的阈值进行分析时，从基线到4%的MVC，总的肌电持续时间呈曲线下降。在某些情况下，MVC阈值每增加1%，持续时间会下降50%-60%。MVC阈值每增加1%，24 h IEMG平均增加1.5%~2%。因此，分析阈值的微小变化可能导致24小时肌电持续时间的较大变化，但平均IEMG的中等变化。我们的发现表明，VL在24小时内具有短时间和低强度的活动。
Klein CS, Peterson LB, Ferrell S, Thomas CK. Sensitivity of 24-h EMG duration and intensity in the human vastus lateralis muscle to threshold changes. J Appl Physiol 108: 655-661, 2010. First published December 10, 2009; doi: 10.1152/japplphysiol. 00757.2009.-Few studies have quantified lower limb muscle activity over 24 h using electromyographic signals (EMG). None have described the changes in EMG duration and intensity when data are analyzed with different thresholds. Continuous bilateral EMG recordings were made from vastus lateralis (VL) in 10 subjects (20-48 yr) for 24 h. Before and after this recording, voluntary quadriceps forces and VL EMG at 25%, 50%, 75%, and 100% of the maximal voluntary contraction (MVC), percentage voluntary activation (twitch interpolation), and compound action potentials (Mwaves) were recorded. Offline, the 24-h EMG integrals (IEMG, 10-ms time constant) were normalized to the MVC IEMG. Total EMG duration and mean IEMG ranged from 1-3 h and 3.2-12.1% MVC, respectively, when the data were analyzed using the baseline (+3 SD) as threshold. When analysis was done with progressively higher thresholds, from baseline up to 4% MVC, the total EMG duration declined curvilinearly. In some cases the decline in duration was 50-60% for a 1% MVC threshold increment. The mean 24-h IEMG increased by 1.5-2% MVC for each 1% MVC threshold increment. Hence, a small change in the analysis threshold may result in large changes in 24-h EMG duration but moderate changes in mean IEMG. Our findings suggest that VL was active for a short amount of time and at low intensities over 24 h.