The Relationship between Muscle Fatigue, Level of Motor Control, and Kinematic Changes in the Accuracy of Skill Performance among Junior Badminton Players

Abstract

This study investigated the effects of muscle fatigue on motor control, kinematic changes, and skill accuracy in junior badminton players. Thirty elite junior players (ages 14–18 years) underwent a badminton-specific fatigue protocol until their maximal voluntary contraction (MVC) declined by approximately 40%. Performance variables were measured pre- and post-fatigue, including reaction time, shoulder proprioception, force steadiness, movement variability, upper limb kinematics, and smash stroke accuracy. The results indicated a significant decline in skill accuracy following the fatigue protocol (Pre: 7.4 ± 1.1, Post: 4.4 ± 1.6, t = 18.67, p < 0.001, Cohen’s d = 2.19). This decline was accompanied by substantial impairments in motor control, evidenced by increased reaction time (Pre: 247.7 ± 23.0 ms, Post: 289.1 ± 28.2 ms, t = −24.31, p < 0.001, Cohen’s d = −1.61) and decreased shoulder proprioception acuity (Pre: 3.0 ± 0.5°, Post: 5.0 ± 0.7°, t = −17.80, p < 0.001, Cohen’s d = −3.20). Kinematic analysis revealed significant reductions in shoulder abduction angle (Pre: 165.3 ± 6.6°, Post: 154.1 ± 8.0°, t = 15.43, p < 0.001, Cohen’s d = 1.53) and elbow extension angle (Pre: 155.6 ± 5.6°, Post: 146.9 ± 6.8°, t = 15.67, p < 0.001, Cohen’s d = 1.40) at contact, leading to a marked decrease in racket head speed (Pre: 37.9 ± 4.8 m/s, Post: 32.0 ± 4.4 m/s, t = 14.67, p < 0.001, Cohen’s d = 1.28). Furthermore, fatigue induced an increase in movement variability (Pre: 3.8 ± 0.9 SD°, Post: 6.1
± 1.1 SD°, t = −17.41, p < 0.001, Cohen’s d = −2.39). Correlation analysis showed that the decline in skill accuracy was significantly associated with the degree of MVC decline (r = −0.420, p < 0.05) and the reduction in racket head speed (r = −0.317, p < 0.10). These findings suggest that muscle fatigue negatively impacts both central motor control mechanisms and peripheral kinematic execution, leading to a breakdown in the coordination required for accurate overhead strokes. The study highlights the need for targeted fatigue-resistance training and proprioceptive conditioning in junior badminton players to maintain skill accuracy during prolonged matches.