Evaluation of MUAP shape irregularity--a new concept of quantification.

A coefficient for quantifying the shape irregularities of the motor unit action potential (MUAP) is introduced. This coefficient is defined as the "length" of action potential curve normalized by the signal's amplitude in such a way that it is independent on duration and amplitude. It characterizes only the MUAP shape. The irregularity coefficient may be used to measure the deviations of the potential from the normal MUAP. The properties of this coefficient and its relation to the conventional parameters describing MUAP shape, viz the number of phases and turns is discussed. The examples of classification of real signals according to this coefficient are presented.