Age-related differences in laterally directed compensatory stepping behavior.
BACKGROUND: Lateral falls are common in older adults and are associated with an elevated risk of hip fracture, compared with falls in other directions. Although rapid stepping movements can play an important functional role in maintaining balance, control of lateral stepping is a complex and demanding motor task. This study examined whether there are age-related differences in the stepping behavior used to recover from lateral loss of balance. METHODS: Rapid stepping reactions were evoked in healthy, active young (aged 20-30 years; N = 10) and older (aged 65-73 years; N = 10) volunteers by means of a sudden unpredictable motion of a platform on which the subject either stood quietly or walked in place. Subjects were instructed to respond naturally. Video analysis was performed to characterize the patterns of limb movement evoked by lateral platform motion. RESULTS: In responding to lateral perturbation of stance, the older adults were much more likely than the young adults to take multiple steps or use arm reactions to regain equilibrium, particularly when attempting crossover steps. During walk-in-place trials, both young and older subjects more frequently used a sequence of side steps rather than crossovers; however, older adults were still more likely to take extra steps or use arm reactions. Collisions between swing foot and stance limb occurred in 55% of walk-in-place trials in older adults versus only 8% in young adults. CONCLUSIONS: Control of lateral-stepping reactions appears to create difficulties for active and healthy older adults above and beyond previously reported problems in controlling forward and backward stepping. Impaired control of lateral-stepping reactions may be an early indicator of increased risk for lateral falls and hip fracture and should be an important consideration in the development of clinical approaches to predicting and preventing falls and related injuries.