Tai Chi's Effect on Lower Extremity Muscle Co-contraction
January 27, 2021 - Tai Chi mind-body exercise has been shown to reduce falls and improve balance and gait, however, few studies have evaluated the role of lower extremity muscle activation patterns in the observed benefits of Tai Chi on mobility.
Harvard Medical School, China Pharmaceutical University and Tel Aviv University teamed up to perform an exploratory analysis of the association between Tai Chi training and levels of lower extremity muscle co-contraction in healthy adults during walking under single-task and cognitive dual-task conditions.
Surface electromyography of the anterior tibialis and lateral gastrocnemius muscles was recorded during 90 sec trials of overground single-task (walking normally) and dual-task (walking with verbalized serial subtractions) walking. A mean co-contraction index (CCI), across all strides, was calculated based on the percentage of total muscle activity when antagonist muscles were simultaneously activated. A hybrid study design investigated long-term effects of Tai Chi via a cross-sectional comparison of 27 Tai Chi experts and 60 age-matched Tai Chi-naive older adults. A longitudinal comparison assessed the shorter-term effects of Tai Chi; Tai Chi-naive participants were randomly allocated to either 6 months of Tai Chi training or to usual care.
Across all participants at baseline, greater CCI was correlated with slower gait speed under dual-task but not single-task walking. Linear models adjusting for age, gender, BMI and other factors that differed at baseline indicated that Tai Chi experts exhibited lower CCI compared to Tai Chi-naives under dual-task, but not single-task conditions. No differences were observed in CCI for Tai Chi-naive adults randomly assigned to 6 months of Tai Chi vs. usual care.
Lower extremity muscle co-contraction may play a role in the observed benefit of longer-term Tai Chi training on gait and postural control. Longer-duration and adequately powered randomized trials are needed to evaluate the effect of Tai Chi on neuromuscular coordination and its impact on postural control.