Reliability of Ankle Isometric, Isotonic, and Isokinetic Strength and Power Testing in Older Women.

The purpose of this study was to examine relative and absolute intrarater reliability of isometric, isotonic, and isokinetic ankle measures in older women. This was a prospective, descriptive methodological study. The following dorsiflexion (DF) and plantar-flexion (PF) measures were assessed twice (7 days apart) by the same examiner in 30 older women: isometric peak torque and rate of torque development (RTD), isotonic peak velocity, average acceleration and peak power, and isokinetic peak torque and peak power. Several statistical methods were used to examine relative and absolute reliability. Intraclass correlation coefficients (ICCs) for the DF tests (ICC=.76-.97) were generally higher than ICCs for matched PF tests (ICC=.58-.93). Measures of absolute reliability also demonstrated more reliable values for DF tests (5%-18%) compared with PF tests (7%-37%). Isotonic peak velocity tests at minimal loads were associated with the lowest CV(TE) and ratio limits of agreement values for both DF (5% and 14%, respectively) and PF (7% and 18%, respectively). Isometric RTD variables were the least reliable (CV(TE)=16%-37%). Limitations This study was limited to a relatively homogeneous sample of older women.

Test-retest reliability was adequate for determining changes at the group level for all strength and power variables except isometric RTD. Minimal detectable change scores were determined to assist clinicians in assessing meaningful change over time in ankle strength and power measurements within individuals.

Webber SC, Porter MM. Reliability of Ankle Isometric, Isotonic, and Isokinetic Strength and Power Testing in Older Women. Phys Ther. 2010 May 20; online article ahead of print

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