Research on Multiple Muscles Synergy Based on Joint Recurrence Quantification Analysis

This study aimed to investigate the multiple muscles coordination at different submaximal voluntary contractions (SVC) during power grip. We recruited 24 healthy and young volunteers (12 males and 12 females). All subjects were asked to grip a hydraulic hand dynamometer and to produce target forces under their 30%, 50%, 70% maximal voluntary contractions (MVC) for at least 10s. Simultaneously, wireless electrodes were used to record surface electromyography (sEMG) signals from eight muscles, including brachioradialis (BR), flexor carpi ulnaris (FCU), flexor carpi radialis (FCR), extensor digitorum communis (EDC), flexor digitorum superficialis (FDS), abductor pollicis brevis (APB), first dorsal interosseous (FDI) and abductor digiti minimi (ADM). Joint recurrence quantification analysis (JRQA) was employed to analyze the sEMG signals by both visualization and quantifications. Results showed that the JRQA parameters in both right and left hand increased with the force level evolving, the difference is statistically significant of right hand, but is not or less for left hand. Contrary to 30% and 50%MVC, the values of JRQA parameters in right at 70%MVC were higher than left hand, and there is no difference between right and left hands at each force level. These results implied that muscles coordination can be flexibly founded on the basis of the amount of force required and the coordination mechanism of right hand and left hand was not the same. This study explored the coordination mechanism of multiple muscles under neurological control and the differences between left and right hands, which can provide some reference for the study of artificial limbs or rehabilitation.