Effects of concurrent and terminal visual feedback on ankle co‐contraction in older adults during standing balance

Abstract

This preliminary investigation studied the effects of concurrent and terminal visual feedback during a standing balance task on ankle co‐contraction, which was accomplished via surface electromyography of an agonist–antagonist muscle pair (medial gastrocnemius and tibialis anterior muscles). Two complementary mathematical definitions of co‐contraction indices captured changes in ankle muscle recruitment and modulation strategies. Nineteen healthy older adults received both feedback types in a randomized order. Following an analysis of co‐contraction index reliability as a function of surface electromyography normalization technique, linear mixed‐effects regression analyses revealed participants learned or utilized different ankle co‐contraction recruitment (i.e., relative muscle pair activity magnitudes) and modulation (i.e., absolute muscle pair activity mag-nitudes) strategies depending on feedback type and following the cessation of feedback use. Ankle co‐contraction modulation increased when concurrent feedback was used and significantly de-creased when concurrent feedback was removed. Ankle co‐contraction recruitment and modulation did not significantly change when terminal feedback was used or when it was removed. Neither ankle co‐contraction recruitment nor modulation was significantly different when concurrent feedback was used compared to when terminal feedback was used. The changes in ankle co‐contraction recruitment and modulation were significantly different when concurrent feedback was removed as compared to when terminal feedback was removed. Finally, this study found a significant interaction between feedback type, removal of feedback, and order of use of feedback type. These results have implications for the design of balance training technologies using visual feedback.