Recovery from a trip in young and older adults : mechanics and control of the support limb
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Falls and fall-related injuries are the cause of serious medical and social problems, especially in the growing elderly population. Tripping over an obstacle is one of the major causes for falls in the elderly. This thesis was aimed to obtain insight in the requirements for a successful recovery reaction after tripping and to understand why older people sometimes fail to meet these requirements and fall. Young and older subjects were tripped over an obstacle during walking over an experimental setup, while wearing a safety harness. The kinematics, dynamics and muscle activity during their balance recovery reactions were measured and compared. A rapid and strong push-off reaction by the support limb appeared to be important for successful balance recovery. Older adults, especially older fallers, were less able to recovery their balance due to a lower rate of change of moment generation in all support limb joints and a lower peak ankle moment. In addition to changes in muscle and tendon properties, a lower rate of muscle activation can reduce the rate of force generation, which can hamper the recovery mechanism and lead to a fall. These results suggest that muscle strength may be a limiting factor in preventing a fall. Strength training, combined with training on a functional level, is indicated in older people with low physical capacities to reduce the risk of falling after a trip.