Dependence of the potentials obtained by averaging of the summated EMG from different factors

The influence of different factors on the parameters of the potentials obtained by averaging the summated EMG of m. biceps brachii and m. soleus, recorded monopolarly with surface electrodes having different leading-off area, is studied. The averaging is triggered by different levels of negative or positive deviation from the zero line. In the case of weak muscle activity, the phases of the averaged potentials are similar to those of the extraterritorial potentials of single motor units, their duration being of the order of the longest of these potentials. At higher efforts the interference partly deforms the averaged potentials, but nevertheless they preserve their dependence on the distance to the motor endplate area, the length and the functional state of the muscles. Averaged potentials undergo characteristic changes during fatigue and upon stopping of peripheral blood supply.