Simulation of electromyographic signals

A technique for simulating electromyographic (EMG) signals is reported. The four step method is physiologically based and begins with the modelling of a cross-section of a muscle. Within this cross-section motor unit territories of various sizes are randomly distributed and within a detection area at the centre of the cross-section individual muscle fibres are modelled and randomly assigned to appropriate motor units. For the motor units with fibres in the detection area, recruitment and firing time behaviours, as a function of an assumed level of contraction, are then simulated. For each active motor unit with fibres in the detection area, motor unit action potentials (MUAPs) are created using a line source volume conductor model. MUAPs can be created for various types of detecting electrodes including concentric and monopolar needle electrodes. Finally, the individual motor unit firing time behaviours and MUAPs are combined to create a complete EMG signal. The routines are interfaced through a series of user-friendly menus and forms, are implemented in C and can be run on any IBM compatible machine. Exemplary data are presented along with results from attempts to evaluate the model. Suggested uses of the simulation package, especially with respect to EMG signal decomposition, are discussed.