Adaptive locomotion during subtle environmental changes in younger and older adults

For older adults especially, to perform everyday activities safely, adaptive locomotion that adjusts basic locomotion pattern according to the environmental features is critical. It is unknown, however, whether their locomotor patterns can be modified when there are subtle environmental changes. We examined adaptive limb movements, focusing on obstacle avoidance and age-related changes during such situations. Younger (102, with a mean age of 27.5 years) and older (101, with a mean age of 78.3 years) participants walked across one obstacle (150 mm height) four different times. The obstacles were then covertly raised or lowered by 10% of the baseline obstacle height (i.e., 165 mm for ascending and 135 mm for descending conditions), and participants were asked to repeat the activity. We measured leading and trailing foot clearances, the vertical distances between toe tips and the upper edge of the obstacle. In the ascending condition, both groups adjusted and raised their limb clearance according to the obstacle height change. Alternatively, foot clearance of the leading limb for the lowered obstacle did not change among the older adults, whereas it changed in the young adults (lowered their clearance). No changes were observed in the trailing foot clearance for the descending conditions in either age group. Our results suggest that when facing environmental changes that compromise safe mobility, individuals can adapt leading limb movement based on subtle environmental changes, irrespective of age. In case of other changes (i.e., in low-risk situations), however, the ability of adaptive locomotion may be affected by aging.