Nakazawa K, Kawakami Y, Fukunaga T, Yano H, Miyashita M
Motor Dysfunction Division, National Rehabilitation Centre for the Disabled, Tokorozawa City, Saitama Prefecture, Japan.
Eur J Appl Physiol Occup Physiol. 1993;66(3):214-20. doi: 10.1007/BF00235096.
To investigate the relative activation of the synergistic muscles during three different types of muscle contraction, the electromyograms (EMG) of two elbow flexor muscles, the biceps brachii (BB) and the brachioradialis (BR), have been compared. To accomplish this eight healthy human subjects performed the following elbow flexions against the same load--concentric, eccentric and isometric contractions. The isometric contractions were performed at three elbow angles: 10, 45 and 90 degrees (0 degree equal to full extension). The EMG were recorded by bipolar surface electrodes, and the relative activation between the two muscles was evaluated as the quotient of mean EMG activities (BR/BB). For the isotonic elbow flexions, BR/BB were calculated at three angle divisions: 0-30 degrees, 30-60 degrees and 60-90 degrees. Results indicated that the relative activation of the BR during the concentric contractions was higher than that of the eccentric contraction, particularly at the extended elbow angles, i.e. the BR/BB of the concentric contractions for the elbow joint angles ranging from 0-30 degrees and 30-60 degrees were significantly greater (P < 0.05) than those of the eccentric contractions. During the isometric and eccentric contractions, the BR/BB at the flexed joint angles tended to be greater than those at the extended angles. In contrast, there were no angle-dependent BR/BB variations during the concentric elbow flexions. Further, changing patterns in the EMG power spectra due to the type of contraction were different between BB and BR. These results indicated that the activation pattern in the two elbow flexor muscles varied with the muscle contraction pattern.
为研究三种不同类型肌肉收缩过程中协同肌的相对激活情况，比较了两块肘屈肌，即肱二头肌（BB）和肱桡肌（BR）的肌电图（EMG）。为此，8名健康受试者针对相同负荷进行了以下肘屈动作——向心收缩、离心收缩和等长收缩。等长收缩在三个肘角度进行：10度、45度和90度（0度等于完全伸展）。通过双极表面电极记录EMG，并将两块肌肉之间的相对激活情况评估为平均EMG活动的商（BR/BB）。对于等张肘屈动作，在三个角度区间计算BR/BB：0 - 30度、30 - 60度和60 - 90度。结果表明，向心收缩过程中BR的相对激活高于离心收缩，尤其是在伸展的肘角度，即肘关节角度在0 - 30度和30 - 60度范围内的向心收缩的BR/BB显著大于（P < 0.05）离心收缩的BR/BB。在等长收缩和离心收缩过程中，屈曲关节角度处的BR/BB往往大于伸展角度处的。相反，在向心肘屈过程中，BR/BB没有角度依赖性变化。此外，BB和BR因收缩类型导致的EMG功率谱变化模式不同。这些结果表明，两块肘屈肌的激活模式随肌肉收缩模式而变化。
