Derivation of reliable electromyograms and their relation to tension in mammalian skeletal muscles during synchronous stimulation

Abstract

There exists a good correlation between the measured electrical activities and isometric twitch tension in the cat soleus muscle during synchronous stimulation. For an unbiased sampling of electrical activities by averaging a number of electromyograms over the muscle concerned, a relation of the form E = 0.98 T + 535 has been established. It is hoped that this relation will prove valuable in clinical application where EMGs are used. Electrode types for EMG pick-up differ in terms of the signal recorded due to the difference in the spatial and temporal addition of individual motor unit firing and the constructional difference of the electrodes. Fine wire pairs are the best for linearity and ease of application. When surface electrodes are used because of their non-invasive nature, care must be exercised to establish the exact relation between EMG and tension. EMG recordings from different sites within a muscle show considerable variation. A more reliable measure can be obtained by external averaging of multiple pairs of electrodes.