Effects of age, available response time and gender on ability to stop suddenly when walking

Background: Injuries may occur during walking when a sudden stop to avoid a gait path obstacle is called for unexpectedly, but cannot be completed in the time available. Little is known about abilities, particularly those of older adults, to stop suddenly. Methods: Twenty young (mean age 23.4 years) and 20 older (72.6 years) healthy and physically active adults with equal numbers of females and males in each age group were studied. While walking straight ahead at approximately 1.3 m/s, they were cued by a light at one of five possible locations to stop as quickly as possible. Subjects were given available response times (ART), the times between the visual cue to stop and potential passage through a virtual wall that was outlined by the array of lights used to cue the subjects, ranging from 375 to 825 ms in 75-ms increments. The rate of success (RS) in completing the stops as prescribed was determined and the effects on RS of age, available response rime and gender were examined. Regression analyses were used to interpolate the RS data. Results: At all ART, older female (OF) subjects had a significantly lower rate of success (RS) than either older male (OM) or young adult (YA) subjects. At an ART of 525 ms, for example, RS was 58% for YA and 51% for OM, but only 23% for OF. The regression analyses suggested that OM in the mean would have needed 10 ms longer and OF 70 ms longer than YA to achieve a 50% RS. No significant gender difference in RS were found among YA. Conclusions: The healthy and physically active older female subjects in this study needed longer available response times, and thus longer available stopping distances, than did the young adults or the older males to succeed as well in stopping suddenly while walking at their comfortable gait speed. (C) 1998 Elsevier Science B.V. All rights reserved.