A method to standardize gait and balance variables for gait velocity.

Many gait and balance variables depend on gait velocity, which seriously hinders the interpretation of gait and balance data derived from walks at different velocities. However, as far as we know there is no widely accepted method to correct for effects of gait velocity on other gait and balance measures. We developed a simple statistical method to obtain gait and balance variables for each participant that are independent of gait velocity. The first step of our standardization method was the transformation of the gait and balance data to obtain a normal distribution and decrease the influence of outliers. Thereafter, we constructed a formula, based on regression analysis that described how these data varied with gait velocity in each participant during walking without an additional task. Last, this formula was used to standardize the gait and balance data for the effect of gait velocity for each individual participant. As example we present the analysis of mediolateral displacements of the trunk in fit elderly people during walking with and without a dual task.