Investigation on the effects of mental fatigue on drop landing motion control in individuals with functional Ankle instability: A biomechanical perspective.

OBJECTIVE: This study examined mental fatigue (MF)'s biomechanical effects on stable/unstable lower extremities in unilateral functional ankle instability (FAI) during single-leg landings.

METHODS: Eighteen unilateral FAI individuals (9 males/9 females) met International Ankle Consortium criteria (CAIT ≤24, anterior drawer test). Kinematic/kinetic data were collected via Vicon motion capture and Kistler force plates during pre-/post-MF single-leg landings (stable/unstable sides). A 2 × 2 repeated-measures analysis of variance (ANOVA) was employed for data analysis.

RESULTS: 1) At the time of initial contact, a main effect of side was observed for hip flexion angle, with significantly smaller values on the unstable side compared to the stable side (p = 0.002). At the time of peak vertical ground reaction force (vGRF), a main effect of MF was identified for hip flexion angle, showing a significant reduction post-MF intervention (p = 0.012). 2) At the time of initial contact, a main effect of MF was detected for ankle plantarflexion angle, which significantly decreased after MF induction (p < 0.001). At the time of peak vGRF, a main effect of MF was observed for ankle inversion angle, with a significant reduction following MF intervention (p = 0.041). 3) The time to stabilization (TTS) was significantly prolonged after MF exposure (p = 0.036). 4) No interaction effects between MF and side were observed (p > 0.05).

CONCLUSION: MF impaired FAI individuals' hip/ankle biomechanics (reduced flexion/plantarflexion/inversion, prolonged stabilization), suggesting compromised motor control and elevated reinjury risks via biomechanical overload. Absent MF-side interactions imply MF's effects are limb-independent. Rehabilitation should address bilateral cognitive load impacts to enhance stability and injury prevention.