Objective To investigate the effect of muscle fatigue on linear and nonlinear dynamics of sEMG from biceps brachii during maximal voluntary isometric contractions.Method Ten young volunteers subjects performed non-fatiguing isometric contractions with four load levels and fatiguing maximal voluntary isometric contractions.Linear and nonlinear analysis were used to examine the sEMG signals and the changes of sEMG signals when MVC decreased to levels of 80% MVC,70% MVC,60%MVC and 50%MVC compared with the signals of sEMG during non-fatiguing contractions.Result Statistical analyses revealed that AEMG and %DET were significantly higher at fatigue states than those at non fatigue states,while MPF and C(n)were significantly lower than those at non fatigue states.With the development of muscle fatigue,MPF and %DET significantly decreased during maximal effort,while AEMG and %DET stayed stable.The interaction of load level and fatigue state for AEMG,MPF and C(n)were significant.Conclusion MPF and C(n)significantly decrease during maximal voluntary isometric contractions.sEMG dynamics between fatigue state and non-fatigue state is significantly different.