A simulation study to investigate the sensitivity of the electromyogram to conduction velocity changes of individual motor units

The sensitivity of a simulated surface electromyogram (SEMG) to changes in conduction velocity (CV) of individual motor units was assessed. Changes in the conduction velocity measurement and the median frequency and spectral compression measures of both the amplitude and power spectra of the SEMG were calculated. Results show that motor units close to the electrodes dominate the SEMG signal. Results also show that for changes in CV of individual motor units the CV measurement and the spectral measures differ. In the case of uniform changes in the CV of all motor units, changes in these measures are similar and unity sensitivity is observed. Indications from this preliminary study highlight the need for care when deducing the physiological significance of changes observed in the SEMG.