Gait initiation: the first four steps in adults aged 20-25 years, 65-79 years, and 80-91 years.

Transitioning from standing to walking requires equilibrium to be maintained while a forward propulsive force is generated. The ability to manage these competing demands is compromised by the progressive sensory, neural and motor declines associated with aging. The purpose of this study was to establish the age-related changes in the first four steps of gait in three age groups: 20-25 years old (yo) (N=19), 65-79 yo (N=11), and 80-91 yo (N=18). Participants stood comfortably and then walked at a self-selected pace for 3.2m. Gait speed and step length (SL) both significantly decreased with each age category at each of the first four steps. However, the gait speed changes suggest that older groups control speed in a principled manner across the four steps, which was similar to the speed control of 20-25 yo. With successive steps, 20-25 yo demonstrated a progressive decrease in SL variability, but SL variability of the two older groups did not change. Step width (SW) did not change as a function of age, but SW variability was higher for the two older groups. Higher SL and SW variability may reflect more errors in foot placement and/or decreased center of mass control in the older groups. Further, it appears that AP COM control improves with successive steps in young adults while ML COM control decreases with successive steps in all age groups. When comparing the two older groups, healthy 80-91 yo walked slower with a shorter SL, but did not demonstrate changes associated with falls (SL and/or SW variability).