Effect of increased motor unit action potential duration on the amplitude and mean power frequency of the electromyogram

A motor unit (MU) pool model was used to simulate surface EMG (electromyogram) for conditions of increased motor unit action potential (MUAP) durations at three levels of contraction. Full-wave rectified average EMG (AEMG) increased and mean power frequency (MPF) decreased with increased MUAP duration. The degree of change in AEMG and MPF depends on the contraction level. However, the relation between change in AEMG and change in MPF was independent of contraction level and may be useful in isolating the effect of increased MUAP durations on EMG amplitude during fatiguing contractions