Interpreting muscle function from EMG:: lessons learned from direct measurements of muscle force
Interpreting muscle function from EMG:: lessons learned from direct measurements of muscle force
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DOI：
10.1093/icb/icn056
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发表时间：
2008-08-01
影响因子：
2.6
通讯作者：
Gabaldon, Annette M.
中科院分区：
文献类型：
--
作者：
Roberts, Thomas J.;Gabaldon, Annette M.
肌电图常用于推断骨骼肌产生力的模式。从肌电图（EMG）的肌肉功能的解释是挑战的事实，如肌纤维的类型，肌肉长度和肌肉速度的因素都可以影响肌肉的电和机械活动之间的关系。同时测量的肌电图，肌肉力量，并在后肢肌肉的肌束长度的野生火鸡，使我们能够探测力和肌电图之间的定量联系。我们研究了两个特点的forceEMG关系。首先，我们测量了松弛机电延迟（r-EMD）作为从EMG信号结束到力结束的时间。这种延迟随外侧腓肠肌（LG）的运动速度而变化;慢速行走时的延迟时间长于跑步时。r-EMD的这种变化不能用肌肉长度轨迹的差异来解释，因为r-EMD的大小与放松过程中肌肉缩短的速度无关。我们推测，与跑步相比，慢速步行时较长的松弛时间可能反映了较慢肌肉纤维松弛的时间过程较长。我们还研究了在步行和跑步速度范围内力的大小和EMG之间的关系。我们分析的forceEMG的关系在摆动阶段分开的forceEMG的关系在站立阶段。在站立时，力的幅度（平均力）与平均肌电幅度（平均肌电）呈线性相关。在摆动阶段的力量低于预测的立场相forceEMG关系。不同的forceEMG的关系在站立和摆动阶段可能反映了被动结构的发展的力量，或在低水平的肌肉活动的非线性forceEMG的关系的贡献。总之，这些结果表明，当考虑到广泛的活动时，必须谨慎地从EMG中推断力。
Electromyography is often used to infer the pattern of production of force by skeletal muscles. The interpretation of muscle function from the electromyogram (EMG) is challenged by the fact that factors such as type of muscle fiber, muscle length, and muscle velocity can all influence the relationship between electrical and mechanical activity of a muscle. Simultaneous measurements of EMG, muscle force, and fascicle length in hindlimb muscles of wild turkeys allow us to probe the quantitative link between force and EMG. We examined two features of the forceEMG relationship. First, we measured the relaxation electromechanical delay (r-EMD) as the time from the end of the EMG signal to time of the end of force. This delay varied with locomotor speed in the lateral gastrocnemius (LG); it was longer at slow walking speeds than for running. This variation in r-EMD was not explained by differences in muscle length trajectory, as the magnitude of r-EMD was not correlated with the velocity of shortening of the muscle during relaxation. We speculate that the longer relaxation times at slow walking speeds compared with running may reflect the longer time course of relaxation in slower muscles fibers. We also examined the relationship between magnitude of force and EMG across a range of walking and running speeds. We analyzed the forceEMG relationship during the swing phase separately from the forceEMG relationship during stance phase. During stance, force amplitude (average force) was linearly related to mean EMG amplitude (average EMG). Forces during swing phase were lower than predicted from the stance phase forceEMG relationship. The different forceEMG relationships during the stance and swing phases may reflect the contribution of passive structures to the development of force, or a nonlinear forceEMG relationship at low levels of muscle activity. Together the results suggest that any inference of force from EMG must be done cautiously when a broad range of activities is considered.