Abstract: Objective To observe the influence of dynamic contractions on the sEMG co-contraction ratio taken from the antagonist muscles of the knee joint of stroke patients.Methods 11 stroke patients and 14 healthy subjects were measured the dynamic contractions in both knee flexion and extension with the surface electromyography(sEMG).Results There was no significant differences of the median frequency(MF),mean power frequency(MPF),average EMG(AEMG)and the sEMG co-contraction ratio within the stroke patients and the healthy(P>0.05).There was no significant difference of the MF between the patients compared with the healthy(P>0.05),but the sEMG co-contraction ratio of the MPF increased significantly and that of AEMG decreased significantly(P<0.01).Conclusion The MPF,AEMG and the sEMG co-contraction ratio taken from the stoke patients may reflect the characters of the low limb muscle and the MF may not.

Key words: stroke, knee joint, antagonist muscles, co-contraction ratio, surface electromyography