Quantitative approach for activation level of skeletal muscle during human daily life of aged peoples

在我们之前的研究中，我们已经观察到衰老会导致肌肉组织萎缩和肌肉功能退化。肌肉萎缩和肌力下降与肌群有关，股四头肌萎缩占主导地位，与其他肌群相比，其膝关节伸展力下降。另一方面，手臂肌肉如肘关节屈肌和伸肌没有显示出与年龄无关的变化。考虑到不同肌肉群对衰老的责任差异，使肌肉在日常生活中有不同程度的激活。然而，到目前为止，还没有关于日常生活中肌肉激活水平估计的研究。因此，本研究的目的是通过肌电图（EMG）来量化日常生活中的肌肉激活水平。取腹直肌、仰卧直肌、股内侧肌、股直肌、股外侧肌、股二头肌、胫前肌、腓肠肌内侧肌等8个肌群每天10小时的肌电记录。为了估计肌肉的激活程度，我们采用了%MVC（最大自主收缩强度）的表达。在正常工作生活的情况下，测量的肌电图显示在工作生活中肌肉激活相对较低，即每个肌肉群的激活低于30%MVC。认为为了防止40%MVC以上的肌肉萎缩作为有效的训练强度，需要在日常生活中增加专门设计的肌肉活动，保持肌肉的体积和功能。

In our previous studies, it has been observed that the aging induces the atrophy of muscle tissue and deterioration of muscle function. The muscle atrophy and deterioration of muscle strength was depend on the muscle groups, i.e.quardriceps femoris muscle indicated dominant atrophy and lowering the knee extension strength compared to other muscle groups. On the other hand, armmuscles such as elbow flexors and extensors indicated no changes independent of age. The differences for responsibility to the aging among muscle groups is considered for the muscle to activate with different levels in daily life. However, so far, there were no studies for the estimation of muscle activation level during daily life. The purpose of the present study is, therefore, to quantify the muscle activation levels during workaday life by means of electromyogram(EMG). EMG recordings during 10 hours a day were obtained from such 8 muscle groups as rectus abdominis, erector supinae, vustus femoris medialis, rectus femoris, vustus lateraris, biceps femoris, tibialis anterior, gastrocnemius medialis. To estimate the level of activation of muscle, we adopted the expression of %MVC (maximal voluntary contraction strength). In the case of normal workaday life, the measured EMG indicated relatively lower muscle activation during workaday life, i.e. every muscle groups activated lower than 30%MVC. It is considered that as to prevent muscle atrophy above 40%MVC is demanded as the effective training intensity, specially designed muscle activity should be added in daily life to keep muscle volume and function.