Computerized synthesis of electromyographic interference patterns.

Computer simulation is a process that appears to have wide application in many disciplines. Electromyographic (EMG) interference patterns can be computer-synthesized by inputting parameters of individual motor unit action potentials (MUAPs) such as amplitude, duration, and phases, and recruitment parameters of number of motor units, and the firing rate and its standard deviation. The resulting simulated EMG interference patterns can then be used to test hypotheses regarding the effect of alteration of the individual MUAP parameters on the interference pattern. An example of the usefulness of simulation is demonstrated by the analysis of the simulated patterns by the Fast Fourier Transform (FFT), which indicates that the major frequency band in the FFT results from the duration of the individual phases of the MUAP. The motor unit's recruitment rate is superimposed on the FFT envelope in the low-frequency end. The variability of the firing rate influences the distinctness of the low-frequency peaks. The MUAP amplitude and number of motor units in the recruitment pattern are reflected in the FFT power. Simulation appears to be a useful tool for further investigation and development of EMG signal analysis techniques.