Evaluation of muscle fatigue at several contraction levels and its application for field assessment

We have proposed a muscle fatigue evaluation method based on the relationship between a superimposed M wave (SM wave) and the preceding background activity. In this paper, we described the application of our method in field assessment based on the results at different contraction levels. At different levels of submaximum voluntary sustained contractions, we estimated the correlation between instantaneous frequency (Ifs) of the SM wave and mean power frequency (MPF) of the preceding background activity. The results showed that the MPF and Ifs were uncorrelated or sometimes showed negative correlation during the low level contractions. Hence, the 30% of maximum voluntary contraction was employed for the assessment of muscle fatigue before and after running exercise. Results of the first day showed the same results of the low level contractions, but they showed the features of muscle fatigue like those at the high level contractions on third day