Purpose: To assess the reliability of neurocognitive and functional performance tests in athletes with and without functional ankle instability (FAI).
Methods: In this methodological study, 20 athletes with unilateral functional ankle instability (mean age [SD]: 23.40[2.58] y; mean height[SD]: 1.77[0.11] m; mean weight[SD]: 67.00[13.18] kg) and 20 uninjured athletes (mean age[SD]: 23.05[2.72] y; mean height: 1.77[0.13] m; mean weight: 66.35[12.21] kg) matched by sex, sports type and level, age, limb dominance, height, and weight were sampled by convenient method from Karaj volleyball and basketball super league members. Functional performance tests (FPTs) included the star excursion balance test (SEBT), figure-of-8, side, square, and single hop tests. Neurocognitive function was assessed with the Deary-Liewald reaction task (DLRT) including simple and choice reaction times and error rate. The intraclass correlation coefficient (ICC) and standard error of measurement (SEM) tests were calculated using SPSS software version 16. 
Results: There were no statistically significant differences between 2 groups with regard to age (P=0.641), weight (P=0.872), height (P=0.989), and duration of physical activity (P=0.94). Generally, high to very high level of reliability were determined with ICC ranging from 0.74 to 0.99, and 0.91 to 0.99 and SEM ranging from 0.03 to 0.69, and 0.00 to 0.03 for hop tests and SEBT, respectively. Furthermore, ICC values ranged from 0.78 to 0.96 and SEM values from 0.24 to 23.77 for neurocognitive test.
Conclusion: Reliability of the FPTs was found to be high to very high in this study. SEBT seems to be a highly reliable and applicable test to use in clinical and research practice. Although not as reliable as the SEBT, hop test seems also to be a reliable tool to assess the dynamic performance of patients with FAI. The results suggest that DLRT has an acceptable reliability for the measurement of neurocognitive function in patients with FAI