AGE EFFECTS ON STRATEGIES USED TO AVOID OBSTACLES

Chen et al.1 found that the rates of success which 24 healthy younger and 24 healthy older adults achieved in not stepping on fixed and suddenly appearing virtual obstacles was adversely affected by reducing their available response time. This paper reports the gait strategies used by those 48 subjects in avoiding the obstacles and the factors associated with falls by four of the subjects. Differences among gait parameters were analysed with respect to age, gender, available response time, and avoidance strategy. Both short- and long-step strategies were used to avoid stepping on the obstacles, but age differences in strategy choice were not significant. The short-step strategy was used more often with shorter available response times. To avoid a fixed obstacle gait was seldom adjusted more than two steps before reaching it; the older adults, however, adjusted their stepping pattern one step earlier than did the younger adults. As the available response time was shortened, the results suggest that older adults had more difficulty than did younger adults in employing the long-step strategy. Although the short-step strategy is easier to employ at short available response times, it becomes a highly risky strategy when combined with a fast walking speed and resulted in actual falls. The results show that in both young and old healthy adults, tripping does not necessarily originate from contacts with a physical obstacle; it can be self initiated.