Obstacle contrast modulates gait behavior in younger and older adults.

PURPOSE: This study investigated how obstacle contrast altered gait behavior of healthy younger and older adults.

METHODS

Twenty normally sighted adults, 11 older (mean [standard deviation] age, 68.1 [5.1] years) and 9 younger (mean [standard deviation] age, 21.1 [2.1] years), walked along a 6-m, black carpeted walkway and stepped over a single obstacle positioned 4 m from the start. The obstacle varied in height (0 [no obstacle], 1, and 19 cm) and contrast (6% ["low"] and 90% ["high"] Michelson contrast). Each subject completed 10 trials for each of the 5 conditions in an unblocked, random order. Lower limb kinematics were recorded using 13 motion capture cameras. Visual acuity and contrast sensitivity were measured. A repeated-measures analysis of variance was used to assess age group differences in trail toe position before crossing, lead and trail foot clearance over the obstacle, lead heel position after crossing, and obstacle crossing speed. Planned comparisons were done with Bonferroni correction. Independent t tests were used to compare vision and survey variables between groups.

RESULTS

Visual acuity was similar in both groups (p=0.17), although contrast sensitivity was better in the younger than older adults (p=0.001). Main effects were found for age: compared with younger adults, older adults showed a farther back trail foot position, greater trail foot clearance, closer lead heel position, and slower obstacle crossing speed (p<0.001 for all effects). Main effects were found for obstacle contrast: compared with low-contrast obstacles, for high-contrast obstacles, the trail foot position was farther back, both lead and trail foot clearance were greater, and lead heel position was closer (p<0.024 for all effects).

CONCLUSIONS

Obstacle contrast impacts gait behavior for younger and older adults. It is possible that the visual characteristics of an obstacle are enhanced for high-contrast obstacles, causing changes to gait behavior that may increase safety.