Variation of Dynamic Muscle Model during Fatigue-Inducing Voluntary Contraction

There has been a paucity of studies to identify the variation of muscle properties due to muscle fatigue, although feature changes of surface electromyographic signals due to fatigue have been reported on. In this paper, we investigated the variation of muscle properties in pre-fatigue condition and post-fatigue condition by using the SEMG and the dynamic muscle model. Five subjects performed index finger isometric abduction contraction by using the first dorsal interosseous (FDI) muscle. After fatigue-inducing contraction, the total twitch duration increased by 30.10%, the contraction time and half relaxation time (RT 1/2) were raised to 7.45% and 13.11%, respectively. These results indicate that the response of the twitch force was slowed and prolonged due to the fatigue-inducing contraction. Our results can be used to monitor and identify the muscle properties of patients in rehabilitation programs.