Does fatigue expose functional deficits in chronic lateral ankle sprain?

[Purpose] The purpose of this study was to examine whether functionally induced fatigue affects balance and vertical jump performance more severely in individuals with a history of unilateral lateral ligament injury to the ankle joint. [Participants and Methods] Twenty-three participants volunteered for the study with the experimental group (EG n=12) comprising injured participants with stability deficits and lack of physiotherapy treatment tested against healthy controls (CG n=11). Balance was assessed via a single leg balance test with open eyes on a force platform. The Center-of-Pressure (COP) excursion on the anteroposterior (Y-axis) and the mediolateral (X-axis) were recorded. Additionally, maximal single-leg vertical jump height (VJH) was assessed on a specific platform. Ankle fatigue was induced through performing the modified Square-hop test until exhaustion. [Results] Patients exhibited significant interaction for Time X Group for the COP on the X-axis. COP-X which did not differ between groups, pre-fatigue, while post-fatigue, it increased significantly in the EG. VJH demonstrated significant pre-fatigue differences between groups, suggesting that deficits in this variable were evident without the need to fatigue the muscles involved. [Conclusion] Fatigue can be useful when balance is tested, since post-fatigue deficits, otherwise obscured in the baseline measurement, can become significant.