Effects of Functional and Mental Fatigues on Landing Kinematics of Athletes With Chronic Ankle Instability

Background and Aims Ankle sprains of moderate to severe intensity can lead to chronic ankle instability and adversely affect landing kinematics. Both functional and mental fatigue are key factors contributing to these alterations. The present study aimed to compare the effects of functional and mental fatigue on single-leg landing kinematics in athletes with chronic ankle instability and healthy individuals. 
Methods In this quasi-experimental study, 48 male athletes aged 18–30 years (24 with chronic ankle instability and 24 healthy) were randomly assigned to four groups: Chronic ankle instability with functional fatigue, chronic ankle instability with mental fatigue, healthy with functional fatigue, and healthy with mental fatigue. The single-leg landing test was performed before and after the fatigue protocols, and kinematic angles (knee valgus, knee flexion, and hip flexion) were analyzed using Kinovea software, version 0, 9, 5 . Data were tested for normality using the Shapiro–Wilk test, followed by two-way mixed ANOVA (group×time) and Bonferroni post hoc analysis. 
Results using (P=0.0001). No significant change observed in the hip flexion angle (P=0.113). In the chronic ankle instability group with mental fatigue, the knee valgus angle also showed a significant increase (P=0.0001), whereas the knee flexion (P=0.061) and hip flexion (P=0.565) angles did not exhibit significant changes. Between-group comparisons indicated that the chronic ankle instability group with functional fatigue exhibited greater increases in knee valgus (P=0.0001) and greater decreases in knee flexion (P=0.0001) compared to the healthy groups. Furthermore, compared to the CAI group with mental fatigue, the changes in knee valgus (P=0.148) and knee flexion (P=0.061) were not statistically significant. 
Conclusion Both functional and mental fatigue affect knee and hip joint kinematics in individuals with chronic ankle instability, particularly by increasing knee valgus and decreasing knee flexion. Functional fatigue had a greater adverse effect, causing more considerable changes in joint alignment. These findings highlight the importance of considering the role of different types of fatigue in lower limb injury prevention strategies.