|Budget Amount *help
¥1,600,000 (Direct Cost : ¥1,600,000)
Fiscal Year 1995 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1994 : ¥1,300,000 (Direct Cost : ¥1,300,000)
The purpose of this study is to measure and estimate muscle fatigue utilizing muscle viscoelasticity change by sitting on a vehicle seat for a long period of time, which is calculated from the biomechanical impedance spectrum. This study deals with a change in muscle fatigue which is transitory, not chronic. An EMG (electromyogram), whose median frequency of spectrum decreases in muscle fatigue and a blood flow, with which a low back is congested, caused by a long time contact of skin surface are also measured in order to analyze the relation between muscle strain and muscle fatigue caused by a worse posture sitting on a vehicle seat.
In 1994, (1) measuring points were determined, which were apt to occur a change of muscle stiffness and (2) blood flow was measured. In 1995, (3) calculation of viscoelasticity of muscle and (4) EMG were measured, and the relation between muscle strain and fatigue caused by a worse posture was made clear. The summary is as follows : (1) muscle viscoelasticity changes around 40mm away from the right and left side of the spinal column between the 3rd and the 4th lumbar vertebra, and between the 4th and the 5th lumbar vertebra, when the biomechanical impedance of low back is measured by sitting on a worse vehicle seat for a long period of time. (2) blood flow changes slightly caused by a skin contact with seat in low back. (3) viscosity and elasticity, calculated from the mechanical impedance spectrum, increase with muscle fatigue. (4) integrated value of EMG increases and median frequency of EMG spectrum decreases in muscle fatigue.
Muscle fatigue was estimated by using Principle Component Analysis with the measured viscoelasticity and EMG,and a new objective muscle fatigue index was proposed. The index suggested an adequate correlation with a subjective fatigue which occurred in low back by sitting on standard and worse vehicle seat for a long period of time.