Alterations in gait dynamics in health and disease: are they independent of gait speed?

A typical feature of many gait disorders is reduced walking speed. More subtle properties of gait rhythm may also be altered. We hypothesized that, independent of gait speed, gait dynamics may provide prognostic and diagnostic utility and offer insight into underlying control mechanisms. To test this hypothesis, we quantified the gait dynamics of healthy controls and subjects with Huntington´s disease, Parkinson´s disease and amyotrophic lateral sclerosis. We then studied the relationship among three different aspects of gait: (a) gait speed and rhythm (stride time), (b) the magnitude of the fluctuations in gait rhythm, and (c) three measures of fluctuation dynamics. The results are: (1) Gait speed, average stride time and stride time variability (fluctuation magnitude) were highly correlated (p <0.0001) with each other. However, much of the variance in each measure was not explained by the association with the other (i.e. r≪1.0). (2). Similarly, the three measures of fluctuation dynamics were significantly correlated with each other (p<0.0001), but were not entirely redundant. (3) The three measures of fluctuation dynamics were independent of gait speed or stride time