Are signals from different motor units correlated?

A model of the surface motor unit action potential (MUAP) combined with the generation of motor unit (MU) firing statistics are used to study the correlation between MUAP trains from different units corresponding to skin surface recording conditions. Simulations of MU firing statistics incorporate MU synchronization levels reported in the literature. The contribution of individual MU pairs to the global myoelectric signal (MES) correlation function is assessed. Results indicate that contributions involving two different MUs decrease steadily becoming small for record lengths as short as 30 seconds. Thus, the error incurred in computing MES correlation functions as the sum of the contributions involving only one MU is also shown to be small.