Specificity of Muscle Fatigue in Hemiplegia and Normal Subjects with E.M.G. Power Spectral Analysis

Abstract

Using an electromyogram, specificity of muscle fatigue was investigated in 6 healthy subjects and 6 hemiplegic patients. Subjects positioned themselves in supine position with the knees slightly flexed and the ankle wearing a weight of 5% body weight, and performed knee extension once per 2 sec for 5 min. Electromyographic data were obtained from vastus medialis muscle before exercise and during 5-sec knee flexion at every 1 min of exercise. The data were processed using Fast Fourier Transform (FFT), and compared by the change rate of Median Frequency (MF). A statistically significant difference in electromyographic data was observed between hemiplegic patients and healthy subjects. In hemiplegic patients, a significant difference in electromyographic data was observed between before exercise and 2 min after the initiation of the exercise; the frequency became lower. The change conformed to the change of secondary function. In healthy subjects, the frequency also became lower, but not statistically significant.