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Abstract

Coordination of functionally coupled muscles is a key aspect of movement execution. Demands on coordinative control increase with the number of involved muscles and joints, as well as with differing movement periods within a given motor sequence. While previous research has provided evidence concerning inter- and intramuscular synchrony in isolated movements, compound movements remain largely unexplored. With this study, we aimed to uncover intermuscular synchrony between homologous muscles during bipedal squatting (BpS) at multiple frequency bands (alpha, beta, and gamma) utilizing intermuscular coherence (IMC) analyses. For this purpose, participants performed bipedal squats without additional load, which were divided into three distinct movement periods. Surface electromyography (EMG) was recorded from 4 homologous muscle pairs representing prime movers during bipedal squatting. We found significant IMC at all frequency bands for all homologous muscles. Importantly, we provide novel evidence that IMC magnitudes differ between movement periods in beta and gamma bands, as well as between homologous muscle pairs across all frequency bands. Here, beta and gamma IMC magnitudes were highest during eccentric movement periods, whereas we did not find movement related modulations for alpha IMC magnitudes. This finding thus indicates increased integration of afferent integration during eccentric movement periods. Collectively, our results shed light on intermuscular synchronization during bipedal squatting, as we provide evidence that central nervous processing of intermuscular functioning is achieved through task-dependent modulations of common neural input to homologous muscles.