Faculty of Sport Sciences, Waseda University, Tokorozawa, Saitama, Japan.
PLoS One. 2012;7(3):e34269. doi: 10.1371/journal.pone.0034269. Epub 2012 Mar 27.
The motor nerve of the bi-articular rectus femoris muscle is generally split from the femoral nerve trunk into two sub-branches just before it reaches the distal and proximal regions of the muscle. In this study, we examined whether the regional difference in muscle activities exists within the human rectus femoris muscle during maximal voluntary isometric contractions of knee extension and hip flexion. Surface electromyographic signals were recorded from the distal, middle, and proximal regions. In addition, twitch responses were evoked by stimulating the femoral nerve with supramaximal intensity. The root mean square value of electromyographic amplitude during each voluntary task was normalized to the maximal compound muscle action potential amplitude (M-wave) for each region. The electromyographic amplitudes were significantly smaller during hip flexion than during knee extension task for all regions. There was no significant difference in the normalized electromyographic amplitude during knee extension among regions within the rectus femoris muscle, whereas those were significantly smaller in the distal than in the middle and proximal regions during hip flexion task. These results indicate that the bi-articular rectus femoris muscle is differentially controlled along the longitudinal direction and that in particular the distal region of the muscle cannot be fully activated during hip flexion.
双关节股直肌的运动神经通常在到达肌肉的远端和近端区域之前，从股神经干分裂成两个分支。在这项研究中，我们检查了在最大自主等长收缩膝关节伸展和髋关节屈曲期间，人类股直肌内是否存在肌肉活动的区域差异。从远端、中间和近端记录表面肌电图信号。此外，通过用最大刺激强度刺激股神经来诱发抽搐反应。每个自愿任务期间肌电图幅度的均方根值被归一化为每个区域的最大复合肌肉动作电位幅度（M 波）。在所有区域，髋关节屈曲时的肌电图幅度明显小于膝关节伸展时的幅度。在膝关节伸展期间，股直肌内各区域的归一化肌电图幅度没有显著差异，而在髋关节屈曲期间，远端的幅度明显小于中间和近端的幅度。这些结果表明，双关节股直肌沿着纵轴方向受到不同的控制，特别是在髋关节屈曲期间，肌肉的远端区域不能被充分激活。
