Test–Retest Reliability of Biodex System 4 Pro for Isometric Ankle-Eversion and -Inversion Measurement

in Journal of Sport Rehabilitation
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The lack of knowledge about isometric ankle testing indicates the need for research in this area.


to assess test–retest reliability and to determine the optimal position for isometric ankle-eversion and -inversion testing.


Test–retest reliability study. Isometric ankle eversion and inversion were assessed in 3 different dynamometer foot-plate 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 d between the tests.


University hospital.


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 (ICC2,1); minimal detectable change (MDC) was calculated using a 95% confidence interval. Paired t test was used to measure statistically significant changes, and P <.05 was considered statistically significant.


Eversion and inversion peak torques showed high ICCs in all 3 angles (ICC values .87–.96, MDC values 3.09–6.81 Nm). Eversion peak torque was the smallest when testing at the 0° angle and gradually increased, reaching maximum values at 14° angle. The increase of eversion peak torque was statistically significant at 7 ° and 14° of inversion. Inversion peak torque showed an opposite pattern—it was the smallest when measured at the 14° angle and increased at the other 2 angles; statistically significant changes were seen only between measures taken at 0° and 14°.


Isometric eversion and inversion testing using the Biodex 4 Pro system is a reliable method. The authors suggest that the angle of 7° of inversion is the best for isometric eversion and inversion testing.

The authors are with the Lithuanian University of Health Sciences, Kaunas, Lithuania.

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