Article

Tripping during locomotion, the leading cause of falls in older adults, generally
occurs without prior warning and often while performing a secondary task. Prior
warning can alter the state of physiological preparedness and beneficially
influence the response to the perturbation. Previous studies have examined how
altering the initial "preparedness" for an upcoming perturbation can affect
kinematic responses following small disturbances that did not require a stepping
response to restore dynamic stability. The purpose of this study was to examine
how expectation affected fall outcome and recovery response kinematics following
a large, treadmill-delivered perturbation simulating a trip and requiring at
least one recovery step to avoid a fall. Following the perturbation, 47% of
subjects fell when they were not expecting the perturbation whereas 12% fell when
they were aware that the perturbation would occur "sometime in the next minute".
The between-group differences were accompanied by slower reaction times in the
non-expecting group (p < 0.01). Slower reaction times were associated with
kinematics that have previously been shown to increase the likelihood of falling
following a laboratory-induced trip. The results demonstrate the importance of
considering the context under which recovery responses are assessed, and further,
gives insight to the context during which task-specific perturbation training is
administered.
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Langue : ANGLAIS