The Impact of Mental Fatigue on Drop Landing Injury Risk and Lower Limb Asymmetry in Elite Collegiate American Football Players

This study investigated the impact of mental fatigue (MF) on lower limb biomechanics and bilateral asymmetry during drop landings in elite collegiate American football players to assess injury risk implications. Twelve elite male players performed bilateral drop landings before and after a 45-minute Stroop task. Data were analyzed using a 2×2 repeated-measures ANOVA. Irrespective of MF, the dominant limb exhibited significantly smaller hip flexion, larger peak vertical ground reaction force (vGRF), and longer time to vGRF peak compared to the non-dominant limb. Following MF, knee flexion range of motion (RoM) and peak vGRF increased bilaterally, and the non-dominant limb specifically demonstrated greater knee varus/valgus RoM compared to baseline. While the symmetry index (SI) indicated baseline asymmetry, MF exerted no significant effect on global SI. We conclude that MF impairs landing mechanics through limb-specific constraints rather than systemic symmetry collapse. Because compensatory strategies preserve global SI, standard indices may mask underlying injury risks under cognitive load. Consequently, athletic screening should prioritize the sensorimotor resilience of the non-dominant limb.