Biomechanical effects of squat depth and movement speed on knee joint loading in Tai Chi novice

Purpose: In this study, the effects of squat depth and movement speed on knee joint loading during the "Part the Wild Horse's Mane" (PWHM) movement in Tai Chi novices were investigated. Methods: Thirteen healthy males performed the movement under six randomized conditions combining three squat depths (high, medium, low) and two speeds (slow and fast). Kinematic and kinetic variables were analyzed using repeated-measures ANOVA, statistical parametric mapping (SPM), and linear mixed-effects models. Results: Increased squat depth significantly elevated knee flexion-extension range of motion (ROM), peak extension moments, and joint impulses in both the sagittal and transverse planes ( p < 0.01). Higher movement speeds resulted in significantly greater flexion and abduction angular velocities as well as peak extension moments, but were associated with reduced joint impulses ( p < 0.01). Significant interaction effects between squat depth and movement speed were observed for flexion-extension and internal-external rotation impulses ( p < 0.05). Among all tested conditions, the combination of medium squat depth and slow movement speed produced relatively lower adduction-abduction impulses compared to other conditions. Conclusions: These findings suggest that moderate-depth squats performed slowly may reduce medial-lateral knee loading and offer a safer strategy for joint protection in Tai Chi training.