ABSTRACT
Objective To explore a new method for evaluating muscle fatigue by analyzing the surface electromyographic(SEMG) signal characteristics and to search for the practical use of SEMG.Methods Four healthy young females performed continuous isometric contractions of vastus medialis at 65? knee extension with 60% MVC for 3 minutes. SEMG signals were recorded from bilateral vastus medialis. The data were analyzed through curve fitting and nonlinear regression.Results All the estimative curves for SEMG parameter in relation to the testing phase are of cubic with the equations of Y=b_0+b_1x+b_2x2+b_3x3. The b1 and b3 in the formula are negative and b2 is positive for MF,MPF,ZCR, whereas the b1 and b3 are positive and b2 is negative for AEMG.Conclusion The cubic curve during muscle fatigue suggests that three main factors may involve in muscle fatigue. The factors were discussed briefly and need to be confirmed further.