Reproducibility of ankle dorsiflexor muscle strength measurements in individuals with post-polio syndrome

Abstract

The aim of this study was to assess the reproducibility of isokinetic and isometric ankle dorsiflexor strength measurements in individuals with post-polio syndrome (PPS). Thirty-one men and women (mean age 63 +/- 7.0 years) with verified PPS, participated in an intra-rater test-retest reproducibility study. Strength of the ankle dorsiflexor muscles in both lower limbs were measured twice, seven days apart, with a Biodex dynamometer (isokinetic concentric; 30 degrees/s and isometric; ankle plantar flexion angle 10 degrees). Reproducibility was evaluated with the intraclass correlation coefficient (ICC2,1), the mean difference between the test sessions ((d) over bar) and the 95% confidence intervals for (d) over bar, the standard error of measurement (SEM, 95% SEM and SEM%) and Bland & Altman graphs. All 31 individuals completed the measurements in the less affected lower limb, but only 14 in the more affected lower limb due to severe weakness and/or joint stiffness. The analysis was therefore based on data from the two lower limbs separately. The test-retest agreements were high, (ICC2,1 0.85 to 0.94) and measurement errors generally small, and there was no discernible difference between the less and more affected lower limbs. The mean isokinetic and isometric peak torque (Nm) for the two lower limbs from the two test sessions ranged from 22.7 to 25.8. The SEM, which represents the limit for the smallest change that indicates a real change for a group of individuals, ranged from 2.51 to 3.74 Nm. In conclusion, isokinetic and isometric muscle strength measurements of the ankle dorsiflexor muscles in individuals with PPS are reproducible and can be used to detect changes over time or after an intervention for groups of individuals. (Less)