Changes in Gait Variability Across the Lifespan in Persons with Down Syndrome.

Abstract

Variability is always present during repetitive movements. Scholars have studied human movement patterns for years, but have only recently begun to focus on variability as something other than noise or error. I followed the theoretical perspective that optimal amount and form of variability in a biological system supports being stable yet adaptable.

I used tools from nonlinear dynamics, Lyapunov Exponent (LyE) and Approximate Entropy (ApEn), to measure form of variability and a traditional linear measure, Coefficient of Variation (CV), to measure quantity of variability. I tested walking patterns in toddlers, preadolescents and older adults with Down syndrome (DS) and typical development (TD). Participants walked on a treadmill at preferred, faster and slower speeds while we collected 3-D movement data. I also assessed changes in overground gait parameters and variability in older adults with DS under common environmental perturbation conditions.

Overall, two themes emerge from the work presented here. The first theme is that preadolescents with DS and TD are more adaptive and flexible in their movement patterns as compared to their older and younger peers. Although the quantity of variability in walking patterns generally decreases from toddlers to preadolescents to adults, preadolescents demonstrate higher ApEn and LyE values than their peers indicating they have learned to use variability to be optimally adaptive.

The exception to this general pattern, however, is step width variability, representing the second major theme of this work. As opposed to a decreasing trend in the amount of variability across the lifespan, preadolescents in both groups produce larger amounts of step width variability than their older and younger peers, possibly reflecting efficient use of the passive pendular dynamics of walking. In addition, participants with DS consistently produced smaller amounts of step width variability than their peers with TD. This robust group difference may reflect that step width is more actively controlled in persons with DS; they are less willing or able to adjust it.

Linear and nonlinear measures reflected less stability in the gait patterns of older adults with DS, and nonlinear measures showed they are less capable than preadolescents with DS at utilizing variability adaptively.