Gait variability measures may represent different constructs

Many measures of gait variability have been reported, but the degree to which such measures are associated and thus represent a common construct is inconclusive. The purpose of this paper is to establish construct validity of commonly used spatio-temporal footfall variability and trunk variability measures taking into account the effect of measurement error. Twenty-three older individuals, aged 80 +/- 5 years performed four repeated walks at preferred speed, 0.97 +/- 0.16 m/s. Gait data were obtained by an electronic walkway and by trunk accelerometry. Of initially 13 variability measures, five satisfied a reliability criterion of ICC >= 0.80 and were included in a subsequent construct validity analysis. Of these, step length variability and step time variability did not correlate significantly, while step length variability correlated closely with anteroposterior interstep trunk variability, and step time variability with vertical interstep trunk variability. Mediolateral interstep trunk variability did not correlate significantly with any of the other measures. This finding supports the notion that this measure may represent still a different aspect of variability. Different gait variability measures representing different constructs should be included in gait analysis to enhance our understanding of variability in gait. (C) 2010 Elsevier B.V. All rights reserved.