Locomotor patterns change over time when exposed to an uneven surface

Abstract

During walking, uneven surfaces impose new demands for controlling balance and forward progression at each step. It is unknown the extent to which walking may be refined given a level of stride-to-stride unpredictability at distal level. Here, we explored the effects of an uneven terrain surface on whole-body locomotor dynamics on immediate exposure and after a familiarization period. Eleven young, unimpaired adults walked for 12 minutes on flat and uneven terrain treadmills. The whole-body center of mass excursion range (COMEXC) and peak velocity (COMVEL), step length and width were estimated. On first exposure to uneven terrain, we saw significant increases in lateral COMEXC and COMVEL, and in the variability of COMEXC, COMVEL and foot placement in both anterior-posterior and medial-lateral directions. Increases in step width and decreases in step length supported the immediate adoption of a cautious, restrictive solution on uneven terrain. After familiarization, step length increased and the variability of anterior-posterior COMVEL and step length reduced, while in the medial-lateral direction step width and COMVEL reduced, alluding to a refinement of movement and a reduction of conservative strategies over time. The variability of medial-lateral COMEXC and COMVEL increased, however, consistent with a release of previously constrained degrees of freedom. Despite this increase in variability, a strong relationship between step width and medial-lateral COM movement was maintained. Our results indicate that movement strategies of unimpaired adults when walking on uneven terrain can evolve over time with longer exposure to the surface.