Delayed decision, harder landing: how mental fatigue alters reactive step biomechanics and joint loading in table tennis players

Objective Mental fatigue (MF) is known to impair psychobiological performance, yet its cross-dimensional impact on the neuromechanical control of reactive athletic movements remains underexplored. This study investigated the effects of MF on the cognitive-temporal and lower-limb biomechanical characteristics of table tennis athletes executing a reactive chasse-step. Methods Twenty-four collegiate table tennis athletes (12 males, 12 females) completed a randomized, counterbalanced crossover study. Participants performed a choice-reaction chasse-step forehand topspin task following either a 45-min stroop task (MF condition) or neutral documentary viewing (Control condition). Three-dimensional motion capture and force plates were synchronized to analyze cognitive-motor timing and lower-limb biomechanics across the initial landing, propulsion, and stabilization phases. Results The Stroop task successfully induced significant subjective mental fatigue ( d = 9.03). Behaviorally, MF was associated with a cognitive-motor time compression effect, significantly prolonging premotor time ( d = 4.26) while reducing chasse-step completion time ( d = 6.03). Biomechanically, the MF condition was characterized by a shift toward a “stiff landing” strategy, decreasing maximum ankle dorsiflexion during initial landing ( d = 0.57) and minimum knee flexion during stabilization ( d = 0.72). Kinetically, this reduced shock absorption was accompanied by substantial increases in peak vertical ground reaction force ( d = 0.75), loading rate ( d = 0.97), and medial-lateral ground reaction force ( d = 0.93). Additionally, peak knee extension moments and proximal joint extension velocities were significantly reduced during the propulsion phase. Conclusion MF is linked to a cognitive delay and motor compression cascade that alters the temporal structure of reactive footwork. This central resource depletion may lead athletes to adopt a rigid landing strategy, sacrificing shock absorption and propulsive efficiency. Consequently, MF is associated with elevated multi-planar joint impact forces, highlighting it as a potential biomechanical risk factor for lower-limb injuries. Ultimately, athletes’ cognitive state should be integrated into routine monitoring to balance performance optimization and injury prevention in high-speed racket sports.