Effects of vertical edge presence on foot trajectory during obstacle crossing in younger and older adults.

Adjusting limb movements when stepping over obstacles is essential to avoid tripping, especially in older adults among whom age-related physical decline increases the risk of falls. This study aimed to determine whether older adults modify their foot movements according to obstacle shape, particularly the presence of a vertical edge, and whether their responses differ from those of younger adults. Data from 12 younger and 13 older adults were analyzed. Participants stepped over obstacles placed 5 m away under four conditions that varied in shape and dimensions. Raised rectangular obstacles with clearly defined vertical edges and raised arch-shaped obstacles without vertical edges were presented in small (2.5 cm high × 8 cm deep) and large (5 cm high × 16 cm deep) sizes. Foot trajectories during the swing phase from toe-off to heel contact were compared using Statistical Parametric Mapping (SPM). Compared with raised arch-shaped obstacles, younger adults raised their leading foot higher when crossing both small and large raised rectangular obstacles, beginning at approximately 30% of the swing phase and continuing until immediately before the obstacle was crossed. By contrast, SPM did not reveal significant differences in foot trajectory patterns between raised rectangular and arch-shaped obstacles in older adults. However, discrete foot-clearance measures at obstacle crossing showed significant shape-related differences in both groups. These findings suggest that trajectory-level adaptation to obstacle shape was less clearly expressed in older adults than in younger adults under the examined conditions and that obstacle-shape effects may be detected differently by full-trajectory and discrete analyses.