A Method of Estimating the Number of Motor Unit Action Potentials by Peak Counting Method in Electromyogram

Abstract

Electromyogram (EMG) is interference waveform of motor unit action potentials (MUAPs) within the detection area. We assumed that value obtained by detecting and counting peaks of the EMG corresponds to number of MUAP included in the EMG. In the previous study, it was known that increase of peak number becomes smaller and the number becomes saturated as muscle contraction level becomes higher. Therefore, we modeled and formulated relationship between numbers of peaks and MUAPs in the EMG and proposed an estimation method using them. For this purpose, the method was applied to simulated and real surface EMGs and the utility was discussed. As the result, in the simulated EMG at eight muscle contraction levels, the estimated value approximated the actual number and the error decreased from 37% to 11% at the maximum contraction levels. In the real surface EMG, the relationship between muscle contraction level and estimated value showed the same tendency as the simulated EMG. Therefore, it was suggested that possibility of estimating the number of MUAP in the EMG by using the method.