Test-retest reliability of Biodex System 4 Pro for isometric ankle eversion and inversion measurement

Abstract

CONTEXT: the lack of knowledge about isometric ankle testing indicates the need for research in this area. OBJECTIVE: to assess test-retest reliability, and to determine the optimal position for isometric ankle eversion and inversion testing. DESIGN: test-retest reliability study. Isometric ankle eversion and inversion was assessed in three different dynamometer footplate positions: 0°, 7° and 14° of inversion, two maximal repetitions were performed at each angle. Both limbs were tested (40 ankles in total). The test was performed 2 times with a period of 7 days between the tests. SETTING: University Hospital PARTICIPANTS: the study was carried out on 20 healthy athletes with no history of ankle sprains. MAIN OUTCOME MEASURES: reliability was assessed using intraclass correlation coefficient (ICC, 2,1), Minimal detectable change was calculated using a 95% confidence interval. Paired t test was used to measure statistically significant changes, and p<0.05 was considered statistically significant. RESULTS: Eversion and inversion peak torques showed high intraclass correlation coefficient (ICC) in all three angles (ICC values 0.865-0.959, MDC values 3,09-6,81 Nm). Eversion peak torque was the smallest when testing at 0º angle, and gradually increased reaching maximum values at 14º angle. The increase of eversion peak torque was statistically significant at 7 º and 14 º of inversion. Inversion peak torque showed an opposite pattern -it was the smallest when measured at 14º angle, and increased at the other two angles, statistically significant changes were seen only between measures taken at 0º and 14º angles. CONCLUSIONS: Isometric eversion and inversion testing using Biodex 4 Pro System is a reliable method. We suggest that the angle of 7º of inversion is the best for isometric eversion and inversion testing.