Article

A sudden underfoot perturbation can present a serious threat to balance during
gait, but little is known about how humans recover from such perturbations or
whether their response is affected by age. We tested the hypothesis that age
would not affect the stepping responses to a nominal 10 degree inversion or
eversion of the stance foot during gait. Twenty-three healthy young (22.7+/-3.35
yrs) and 18 healthy old adults (68.0+/-7.19 yrs) performed 60 walking trials
along a 6-m level walkway at a normal gait speed. In 16 of these trials, a single
medial (MP) or lateral (LP) perturbation was randomly administered once under the
left or right foot. Recovery step width (SW), step length (SL), trunk kinematics
and walking speed were measured optoelectronically. Repeated-measures analysis of
variance and post hoc t-tests were used to test the hypotheses. The results show
that a MP or LP altered the recovery SL (p=0.005) and age affected the number of
recovery steps (p=0.017), as well as the first recovery SW and SL (p=0.013 and
p=0.031, respectively). Both MP and LP caused young adults to have wider SW
(p<0.02) and shorter SL (p<0.005) without changing trunk movement during their
first recovery step. Older adults, however, significantly changed lateral trunk
inclination during the first recovery step, decreased their fourth recovery SL
(p<0.001). We conclude that young adults adjust the step kinematics of as many as
four recovery steps following this perturbation, a response that was delayed and
significantly weaker in older adults who instead exhibited an immediate torso
inclination consistent with a hip response strategy.
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Langue : ANGLAIS