Motor unit estimates based on the automated analysis of F-waves

The number of motor units (MUs) in a muscle can be estimated by dividing size-related parameter values measured from a maximal M-Wave by corresponding parameter values measured from an average surface-detected motor unit action potential (S-MUAP). The accuracy of the estimate is dependent on how representative the average S MUAP is of the population of S-MUAPs which contributed to the maximal M-Wave. F-Wave responses have been shown to represent the full range of S-MUAP sizes. An automated system has been developed to obtain a maximal M-Wave, to extract a sample of F-Wave responses, to compute an average S-MUAP and to estimate the number of MUs in a muscle. The technique is well tolerated by subjects, requires little operator interaction, is physiologically sound and is a practical tool for estimating the number of MUs in a muscle.