Inter-Joint Coordination Patterns of the Kicking-Leg Lower Limb During Competitive Taekwondo Side Kicks

Side kick (SK) is among the most frequently used techniques in Taekwondo, and bilateral inter-joint coordination of the lower limbs may influence SK performance. This study investigated whether inter-joint coordination patterns and coordination variability differ between the Dominant side (DS) and Non-Dominant side (NS) during effectively scored SKs in competitive athletes. Twelve male Taekwondo athletes performed SKs while kinematics were captured using a Vicon three-dimensional motion-capture system; scoring outcomes were recorded via Daedo electronic body protectors. Inter-joint coupling angles and coordination variability were computed from kinematic data using custom MATLAB scripts. Coupling-angle distributions were analyzed with circular statistics, and coordination variability was compared using paired t-tests. Compared with the DS, the NS exhibited significant differences in hip–ankle coordination on both frontal and sagittal planes during the initiation phase; in sagittal-plane hip–ankle and hip–knee coordination during the knee-lift phase; and in frontal-plane hip–ankle coordination during the extension phase. Coordination variability on the NS was lower than on the DS during initiation and knee-lift, but higher during extension. These findings indicate bilateral laterality in lower-limb inter-joint coordination and its variability when athletes perform SK with both limbs. The NS appears to adopt adaptive compensatory strategies—alternating between proximal-insufficiency/distal-compensation and distal-insufficiency/proximal-compensation—creating phase-specific windows of elevated risk. These insights may inform targeted, limb- and phase-specific training to optimize performance and mitigate injury risk.