Abstract

The quantification of muscle fatigue is a very important subject in the field of orthopedics, rehabilitation, human science and so on. This paper describes a quantification and subjective estimation of muscle fatigues. Among various causes of the muscle fatigue, the authors take note of changes in muscle stiffness. The elasticity (μ_1) and viscosity (μ_2) of muscle are measured on the low back, in order to estimate the muscle stiffness changes caused by sitting on the vehicle seat for a long time. The viscoelasticity is obtained from the response of the random vibration applied on the skin surface. Moreover MNF (Median Frequency) and IEMG (Integrated EMG) are calculated from EMG wave form. The subject sits on the standard seat and the worse seat apt to cause the muscle fatigue. The authors propose the objective muscle fatigue index based on the PCA (Principal Component Analysis) of the differences of the muscle stiffness and EMG between the standard seat and the worse seat.