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

在我们以前的研究中，已经观察到衰老导致肌肉组织萎缩和肌肉功能恶化。肌肉萎缩和肌力下降取决于肌群，即股四头肌与其他肌群相比表现为显性萎缩和膝关节伸展强度降低。另一方面，手臂肌肉，如肘屈肌和伸肌，没有显示出独立于年龄的变化。肌肉群对衰老的反应性差异被认为是肌肉在日常生活中以不同水平激活的原因。然而，到目前为止，还没有研究评估日常生活中的肌肉激活水平。本研究的目的是，因此，量化的肌肉激活水平在工作生活中通过肌电图（EMG）。记录腹直肌、仰卧起肌、股内侧肌、股直肌、股外侧肌、股二头肌、胫骨前肌、腓肠肌内侧肌8个肌群的肌电，每天10小时。为了估计肌肉的激活水平，我们采用%MVC（最大随意收缩强度）的表达。在正常工作生活的情况下，所测量的EMG显示在工作生活期间相对较低的肌肉激活，即每个肌群的激活低于30%MVC。认为要防止肌肉萎缩，有效的训练强度应在40%MVC以上，日常生活中应增加专门设计的肌肉活动，以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.