The effect of fatigue on lower limb coordination characteristics in badminton forehand smash: a functional principal component analysis

The study of motor coordination explores how the central nervous system controls body movements. Using functional principal component analysis (FPCA), this study examined the impact of fatigue on limb coordination synergies and activity coefficients in 23 badminton players performing forehand smashes before and after fatigue. Kinematic data revealed that pre-fatigue, three coordination synergies effectively controlled all lower limb joints, while post-fatigue, four synergies were required, reflecting increased control complexity. Fatigue significantly altered synergy control: Synergy 2's control of the hip joint decreased, control of the right ankle increased (p < 0.05), and Synergy 3's control of the left ankle decreased (p < 0.05). Fatigue also shifted synergy activity, enhancing Synergy 3 control during landing while reducing Synergy 1 control in the follow-through. These findings highlight how fatigue modifies coordination strategies, increasing joint control complexity, with implications for training to enhance performance stability and reduce injury risks.