Circumvention of suddenly appearing obstacles in young and older adults

Reduced ability to circumvent an obstacle, which is noticed only shortly before collision, could be a cause of falls and injury, especially in older adults. In this study, we investigated differences in strategies and their characteristics between young and older adults when circumventing a suddenly appearing obstacle. We measured young and older adults while walking over a platform, while in some trials an obstacle suddenly appeared halfway, blocking their passage. Obstacle appearance was timed to provide available response times (ART) of 850, 1000 or 1150 ms. Circumvention strategies could be classified as either side stepping or cross-over stepping, which were observed in both age groups. Strategy choice was affected by ART and age; older adults preferred the side step strategy, especially when ART was shorter. Peak ground reaction forces were higher for the side step strategy. Older adults performed similar circumvention strategies as young adults, with a stronger preference for side stepping. This strategy appears to be more stable, although it is more demanding in terms of force generation