Simulation of MUAP Recruitment and Rate Coding in Frequency Domain

In this study, the power spectrum of surface electromyographic signal (sEMG) was used to analyze the motor unit (MU) recruitment and rate coding during isometric voluntary muscle contraction. The MUs were sorted into four different groups, based on the motor unit electrode territory distance (ETD), and four different MUAP waveforms were then provided accordingly. The recruitment threshold and the action potential (MUAP) of MUs which locate farther away from surface electrodes were supposed to be lower in amplitude and frequency than those which locate closer to the surface electrodes, according to the experimental evidence and simulation results. The power spectrum of sEMG was then simulated with linear dynamics model at different voluntary contraction levels. It is shown that this method provides more reasonable results than traditional approaches.