Comparing Upper Limb Intermuscular Coherence between Force- and Myoelectric-Control Tasks

Synchronization between muscles caused by shared neural input has been proposed to have a functional significance in muscle coordination. In this study, intermuscular coherence (IMC), a measure of shared neural input to muscles, was used to explore the neural underpinnings of proximal arm muscle coordination in force- and myoelectric-control tasks. In force-control, the goal was to attain a force magnitude and direction, whereas in myoelectric-control, the goal was to have single or pairwise muscle activation. Muscle coordination was assumed to be more selective in myoelectric-control, being that this task imposed stricter requirements in muscle activation. Accordingly, the expected difference in muscle coordination would be reflected in IMC if shared neural input results from a neural strategy for motor control. The hypothesis was that when single muscle activation was required, IMC in myoelectric-control would be lower than in force-control. Opposite to this, when pairwise muscle activation was required, IMC would be higher in myoelectric-control. Therefore, the presence or not of shared neural input was thought to be the mechanism to correspondingly couple or decouple muscle activation. The main finding was that there was no significant difference in IMC between force- and myoelectric-control tasks for both single and pairwise muscle activation conditions. Furthermore, IMC in single muscle activation was higher than that of pairwise muscle activation conditions in both tasks. Finally, the bands in which IMC was increased were the alpha-band and lower part of the beta-band. These findings are interpreted as that neural constraints have a fundamental role in the distribution of shared neural input to proximal muscles, and thus to their coordination.Biomedical Engineering | BioMechatronic