Simulation of the normal concentric needle electromyogram by using a muscle model

Objectives: To study the correlation between anatomical parameters and EMG signals by means of simulations. Methods: A mathematical model of the electrical activity from muscle fibres and motor units has been developed. The electrical fields around the muscl e fibres are simulated using a line source model. The model permits the sim ulation of single muscle fibre action potentials obtained by SFEMG, concent ric and Macro EMG electrodes. By using appropriate anatomical parameters EM G recordings with these electrodes can be simulated. The model is flexible and permits a number of anatomical parameters to be changed such as; number of muscle fibres in a motor unit, fibre diameter distribution, and motor e nd-plate geometry. Some physiological parameters can be optionally varied; firing rate, threshold for recruitment, jitter. Results: In this study, simulations of CNEMG are performed and the influenc e of a number of parameters on the CNEMG signal is studied. It is shown tha t the model produces motor unit potentials reasonably well resembling those from live recordings. Mon important is however the relative change in MUP parameters when certain conditions are changed; number of muscle fibres in a motor unit, recording position, muscle fibre diameters and some special e ffects of the recording conditions. Conclusions: The simulated muscle and corresponding EMG recording can be us ed both as a research tool and for teaching. (C) 2001 Elsevier Science Irel and Ltd. All rights reserved.