FREQUENCY CHARACTERISTICS IN ISOTONIC MUSCULAR CONTRACTIONS FROM CORRELATION FUNCTION AND FOURIER TRANSFORMATION OF SURFACE ELECTROMYOGRAM (THE SECOND REPORT)

Abstract

Analytical method of correlation function and Fourier transformation has been applied for surface electromyogram. This study is to be aimed to investigate relation between motor-activities in isotonic muscular contractions and frequency in muscular electric discharge. By help of digital electrical computer, frequency characteristics in isotonic contraction of M. Biceps Brachii and M. Rectus Femoris have been calculated as Power Spectrum Density clearly and quantitatively.
As the result of this study, following points were revealed.
1) Fourier transformation was cleared up as the available method of physical fitness research in interpretation of surface electromyogram, on the assumption whose phenome-non was stationary in the process of statistical probability.
2) Upon isotonic contraction, high and low frequency bands were divided distinctly among muscular discharge of surface electromyogram, that were about 20Hz and 75-90 Hz bands.
3) In proportion to intensities of load and to alteration of movement velocity, high discharge frequency band showed changes of ranges of ±15Hz, but low discharge frequency band showed no change.
4) In high discharge frequency band, density of Power Spectrum of M. Biceps Brachii was larger than that of M. Rectus Femoris, but on the other hand of low dis-charge frequency band, this Power Spectrum displayed no difference between both muscles.
5) Comparing with two sorts of muscular contraction, that were isotonic and isometric, high discharge frequency band of the former was higher about 10Hz than that of the later.
6) It was supposed that this low frequency band was dependent upon tonic Neuro Muscular Units and was corresponding to slow contraction of red-colored muscles.
7) It was considered that this high frequency band depended on phasic N.M.U. and had connection with quick contraction of pale-colored muscles.