Muscle Synergies for Motor Control Evaluation

Muscle synergies have been proposed to be a modular organization for muscle coordination that map high-level task goals, or motor intentions, into motor actions. Muscle synergies and other types of modular organization have been used to explain muscle coordination during a variety of motor behaviors in many different species. In some instances, new synergies may emerge when a new motor task is presented and the recruitment of the synergies may be altered. Here, we used a database to investigate muscle activity of the right hand during seven distinct limb motions in order to extract muscle synergies: hand open, hand close, supination, pronation, wrist flexion, wrist extension, and rest. Database content EMG signals collected from seven sites on the forearm and one site on the bicep, with an electrode placed on the wrist to provide a common ground reference. Classification scheme is based on the synergies between a functional group of muscles. The muscular synergy is evaluated using different techniques like the normalized power spectral densities (PSD), the cross-correlation matrix of muscular force (estimated through the root mean square (RMS) value of EMG amplitude) and the intermuscular coherence between different sets of muscles. We investigate the relationship between muscle synergy recruitment and functional motor outputs and hypothesized that a common pool of muscle synergies producing consistent task-level biomechanical functions is used to generate different motor behaviors.