Simulation of the normal concentric needle electromyogram by using a muscle model.
OBJECTIVE
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 muscle fibres are simulated using a line source model. The model permits the simulation of single muscle fibre action potentials obtained by SFEMG, concentric and Macro EMG electrodes. By using appropriate anatomical parameters EMG 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 end-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 influence of a number of parameters on the CNEMG signal is studied. It is shown that the model produces motor unit potentials reasonably well resembling those from live recordings. More 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 effects of the recording conditions.


CONCLUSIONS
The simulated muscle and corresponding EMG recording can be used both as a research tool and for teaching.
Department of Clinical Neurophysiology, University Hospital, SE-751 85, Uppsala, Sweden. erik.stalberg@nc.uas.lul.se
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Stålberg
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Karlsson
D004566:Electrodes; D004576:Electromyography / Q000379:methods* / Q000592:standards; D006801:Humans; D008954:Models, Biological; D009045:Motor Endplate / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D018482:Muscle, Skeletal / Q000166:cytology / Q000294:innervation / Q000502:physiology; D009339:Needles; D015203:Reproducibility of Results