Abstract / Summary
Abstract Long-term unilateral dominant training in Tai Chi is commonly associated with lower-limb functional asymmetry in elite athletes, which may correlate with reduced movement proficiency and increased injury susceptibility. This study recruited 80 elite junior male Tai Chi athletes to investigate the associations between asymmetries in body composition, explosive power, dynamic balance, and task-specific neuromuscular activation and stomping technique performance, aiming to provide biomechanical evidence for targeted physical conditioning and technical optimization. This study utilized a Noraxon MR3 wireless surface electromyography system, Kistler 3D force plates, and a motion capture system to evaluate lower-limb functional asymmetry. The testing protocol included body composition (BC) assessment, single-leg countermovement jump (SLCMJ), Y-Balance test (YBT), surface electromyography (sEMG), and a stomping technique test. The bilateral strength asymmetry index (BSA) for each variable was calculated as: $$ {\text{BSA}} = \left( {\frac{{{\text{Dominant~limb}} - {\text{Non - dominant~limb}}}}{{{\text{Dominant~limb}}}}} \right) \times 100{\text{\% }} $$ . Paired-samples t-tests compared dominant and non-dominant limbs across all measures, with corresponding p-values, Cohen’s d effect sizes, and 95% confidence intervals. Multiple linear regression analysis examined the relationships between BSA variables and stomping technique performance. Predictor variables were selected a priori based on biomechanical hypotheses. The Bonferroni correction was applied to control Type I error for multiple comparisons. (1) The mean BSA for the upper extremity (BSA-UE) was 9.21% (95% CI: 8.49%–9.93%), and for the lower extremity (BSA-LE) was 13.85% (95% CI: 13.15%–14.55%). (2) The SLCMJ yielded mean asymmetry indices of 9.72% (BSA-Fx, 95% CI: 7.92%–11.52%), 9.36% (BSA-Fy, 95% CI: 7.77%–10.95%), and 16.71% (BSA-Fz, 95% CI: 14.96%–18.46%), with significant inter-limb differences in power production across all three directions ( p < 0.05, Cohen’s d = 0.28–0.35). (3) The YBT recorded average bilateral asymmetry index values of 3.23% (anterior, BSA-AT, 95% CI: 2.61%–3.85%), 3.14% (posteromedial, BSA-PM, 95% CI: 2.51%–3.77%), and 3.28% (BSA-PL, 95% CI: 2.64%–3.92%). Significant inter-limb differences in raw reach distance were observed in all three directions ( p < 0.05, Cohen’s d = 0.26–0.39). (4) sEMG recordings revealed significant inter-limb differences in normalized iEMG and muscle contribution ratios for the gluteus maximus, rectus femoris, rectus abdominis, tibialis anterior, and gastrocnemius ( p < 0.05, Cohen’s d = 0.26–0.81). (5) Regression analyses indicated significant cross-sectional associations of BSA-LE, BSA-Fz, and BSA-PL with stomping technique performance ( p < 0.05), with all significant regression coefficients reported with corresponding 95% confidence intervals. Elite junior male Tai Chi athletes exhibit marked lower limb asymmetry. These athletes also present substantial bilateral differences in lower-limb explosive power and dynamic reach performance, as well as divergent muscle activation contribution ratios between dominant and non-dominant limbs. Bilateral asymmetries in lower limb physical characteristics, explosive force, and posterolateral reach capacity are cross-sectionally correlated with stomping technique performance among Tai Chi athletes. These findings highlight the potential value of asymmetry-monitoring strategies in training programs for junior Tai Chi athletes, though future longitudinal studies are warranted to establish whether reducing these asymmetries can improve performance.