Rainoldi A, Falla D, Mellor R, Bennell K, Hodges P
Motor Science Research Center, SUISM Università degli Studi di Torino, P.za Bernini 12 10143, Torino, Italy.
J Electromyogr Kinesiol. 2008 Dec;18(6):1032-7. doi: 10.1016/j.jelekin.2007.05.008. Epub 2007 Jul 17.
The purpose of this study was to determine whether surface electromyography (EMG) assessment of myoelectric manifestations of muscle fatigue is capable of detecting differences between the vastus lateralis and medialis muscles which are consistent with the results of previous biopsy studies. Surface EMG signals were recorded from the vastus medialis longus (VML), vastus medialis obliquus (VMO) and vastus lateralis (VL) muscles during isometric knee extension contractions at 60% and 80% of the maximum voluntary contraction (MVC) for 10s and 60s, respectively. Initial values and rate of change of mean frequency (MNF), average rectified value (ARV) and conduction velocity (CV) of the EMG signal were calculated. Comparisons between the two force levels revealed that the initial values of MNF for the VL muscle were greater at 80% MVC compared to 60% MVC (P<0.01). Comparisons between the vasti muscles demonstrated lower initial values of CV for VMO compared to VL at 60% MVC (P<0.01) and lower than VML and VL at 80% MVC (P<0.01). In addition, initial values of MNF were higher for VL with respect to both VML and VMO at 80% MVC (P<0.01) and initial estimates of ARV were higher for VMO compared to VML at both force levels (P<0.01 at 60% MVC and P<0.05 at 80% MVC). For the sustained contraction at 80% MVC, VL demonstrated a greater decrease in CV over time compared to VMO (P<0.05). These findings suggest that surface EMG signals and their time course during sustained isometric contractions may be useful to non-invasively describe functional differences between the vasti muscles.
本研究的目的是确定通过表面肌电图（EMG）评估肌肉疲劳的肌电表现，是否能够检测出股外侧肌和股内侧肌之间的差异，这些差异与先前活检研究的结果一致。在等长膝关节伸展收缩过程中，分别于最大自主收缩（MVC）的60%和80%时，从股内侧长肌（VML）、股内侧斜肌（VMO）和股外侧肌（VL）记录表面EMG信号，持续时间分别为10秒和60秒。计算了EMG信号的平均频率（MNF）、平均整流值（ARV）和传导速度（CV）的初始值及变化率。两种力量水平之间的比较显示，与60%MVC相比，VL肌肉在80%MVC时MNF的初始值更高（P<0.01）。股肌之间的比较表明，在60%MVC时，VMO的CV初始值低于VL（P<0.01），在80%MVC时低于VML和VL（P<0.01）。此外，在80%MVC时，VL相对于VML和VMO的MNF初始值更高（P<0.01），在两种力量水平下，VMO的ARV初始估计值均高于VML（60%MVC时P<0.01，80%MVC时P<0.05）。在80%MVC的持续收缩过程中，与VMO相比，VL的CV随时间下降幅度更大（P<0.05）。这些发现表明，在持续等长收缩过程中的表面EMG信号及其时间进程，可能有助于非侵入性地描述股肌之间的功能差异。
