Objective: The purpose of this study was to investigate effects of visual feedback on bimanual force control and motor unit discharge patterns in healthy young adults. Method: Thirteen healthy young participants performed bimanual isometric force control tasks while recording decomposition electromyography data from both flexor digitorum profundus muscles under two visual conditions (vision and no-vision). To estimate force control capabilities, we used the relative root mean square error (rRMSE) and coefficient of variation (%CV). For motor unit activation patterns, mean and %CV of inter-spike intervals (ISI) were calculated. For statistical analysis, we conducted a paired t-test on rRMSE and two-way repeated measures ANOVAs (Vision condition × Hand dominant; 2 × 2) on force variability and motor unit activation patterns. Results: When visual feedback was removed, force accuracy (rRMSE) decreased and force variability (%CV) increased. For motor unit activation patterns, there was no significant difference in mean ISI between vision conditions, whereas increased discharge variability (%CV ISI) was observed in no-vision condition as compared with vision condition. Conclusion: These findings suggest that the absence of visual feedback interferes with bimanual force control capabilities and motor unit discharge patterns.
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