Finite limb dimensions and finite muscle length in a model for the generation of electromyographic signals.

A volume conductor model is presented in which the aspects of finite volume conductor dimensions and finite muscle fiber length are combined. The effects of these aspects on single muscle fiber action potentials (SFAPs) and on motor unit action potentials (MUAPs) are shown and verified with surface recorded motor unit action potentials. It is demonstrated that the influence of the fiber length being finite is enhanced significantly by the finite limb dimensions of the volume conductor model, for single fiber action potentials as well as for motor unit action potentials. The model described is found to be capable of generating surface MUAPs which show a very good resemblance with measured surface MUAPs. Recorded MUAPs illustrate clearly the effects caused by finite muscle fiber length. The effect of finite limb dimensions in simulated intramuscular MUAPs was evidently less dominant than in simulated surface MUAPs.