Trial-to-trial reproducibility and test-retest stability of two dynamic balance tests among male firefighters.

The aim of this study was to evaluate a dynamic stability test and a functional balance test for trial-to-trial reproducibility and stability over time. In the dynamic stability test a subject stood on the force platform and moved his center of pressure through the targets shown on a computer screen. Functional balance was measured by a test in which the subject had to walk as fast as possible across a wooden plank without falling off. Both tests are repeated six times in two testing periods with an interval of two months. The subjects were 29 male firefighters aged 33 - 56 years. According to intraclass correlation coefficients the functional balance test showed good to excellent (0.78 - 0.96) trial-to-trial reproducibility and stability over time, and the results of the dynamic stability test were moderate (0.16 - 0.81). Individual variation in the repeated tests was considerable. However, the limits of agreement in the functional balance test (+/- 2 - 3 s) and in the performance time of the dynamic stability test (+/- 4 - 5 s) would be reasonable for practical use. Furthermore, the test-retest stability improved when the reliability was estimated from the best of at least three repeated trials with the functional balance test and the best of at least five trials with the dynamic stability test.