Article

The purpose of this study was to investigate the effects of age on
compensatory-stepping thresholds and dynamic stability maintenance in response to
postural disturbances. It was hypothesized that, with older age, anterior but not
posterior stepping thresholds would be reduced. Thirteen young adults (31.1 +/-
0.8 years), 11 middle-aged adults (57.6 +/- 2.5 years), and 11 older adults (73.8
+/- 5.3 years) participated in this study. Surface translations were delivered as
subjects stood on a microprocessor-controlled treadmill. Subjects were instructed
to "try not to step". Stepping thresholds were defined as the largest
displacement at a given peak treadmill-belt velocity for which a subject could
prevent stepping. The margin of stability was calculated to estimate the minimum
dynamic stability at the stepping thresholds. Age-related declines in the ability
to prevent forward steps were apparent. Anterior stepping thresholds were reduced
with age. The minimum margin of stability associated with anterior stepping
thresholds was not influenced by age. Therefore, smaller disturbance
displacements caused middle-aged and older subjects to become dynamically
unstable to the point of stepping. Posterior stepping thresholds were not
influenced by age. It is concluded that an age-related decline in anterior, but
not posterior, stepping thresholds was due to an impaired ability to maintain
dynamic stability after a disturbance.
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Langue : ANGLAIS