On Correlation between the neural drive to muscles and multichannel surface electromyogram amplitudes

Abstract

Amplitude of surface electromyogram (EMG) has often been used as a measure of neural drive sent to skeletal muscle, especially for assessment of muscle co-activations. In this study, we analyze correlation between the multichannel EMG amplitudes and cumulative motor unit spike train (CST) as assessed by decomposition of surface EMG of writ flexors and extensors in 27 Parkinsonian tremor patients. We demonstrate that in involuntary contractions surface EMG amplitudes vary significantly with the location of the measuring electrodes and that the first principal component of the EMG amplitudes correlates with the CST only in about one third of cases studied and when its relative energy is high.