Characteristics of Finger Muscle Activity Due to Differences in Wrist Joint Alignment: A Study Using Surface Electromyography

Background: In 2017, Tanabe et al. developed a technique to activate the extensor digitorum communis in hemiplegic stroke patients. However, there has not yet been sufficient analysis of this technique for activating the extensor muscles. Therefore, this study aimed to apply this method to healthy subjects and clarify the activity of the flexor and extensor muscles using surface electromyography. Method: This study included 17 healthy subjects. Surface electromyography was measured for the extensor digitorum communis and flexor digitorum superficialis muscles while participants pushed forward under three conditions: condition 1 (wrist dorsiflexion), condition 2 (wrist neutral), and condition 3 (wrist palmar flexion). The data obtained from surface electromyography was digitally processed and divided by maximum muscle output to calculate the % maximal voluntary contraction (%MVC). Additionally, the simultaneous co-contraction index (%CCI) was calculated. The %MVC and %CCI for each condition were analyzed using a Friedman test, with a Dunn test conducted as a post-hoc analysis. Results: Significant differences (P Conclusion: The muscles acting on the fingers were selectively affected by the positional relationship of the wrist. This confirms that the method developed by Tanabe et al. for activating the extensor digitorum communis can effectively promote its activation.