Article

The control of mediolateral dynamic stability during stepping can be particularly
challenging for older adults and appears to be related to falls and hip fracture.
The specific mechanisms or control challenges that lead to mediolateral
instability, however, are not fully understood. This work focussed on the
restabilisation phase of volitional forward stepping, subsequent to foot contact,
which we believe to be a principal determinant of mediolateral dynamic stability.
Twenty younger (age 24+/-5 years; 50% women) and 20 older participants (age
71+/-5 years; 50% women) performed three different single-step tasks of various
speed and step placement, which varied the challenge to dynamic stability. The
trajectory of the total body centre of mass (COM) was quantified. Mediolateral
COM incongruity, defined as the difference between the peak lateral and final COM
position, and trial-to-trial variability of incongruity were calculated as
indicators of dynamic stability. Older adults exhibited increased instability
compared to young adults, as reflected by larger COM incongruity and
trial-to-trial variability. Such increases among older adults occurred despite
alterations in COM kinematics during the step initiation and swing phases, which
should have led to increased stability. Task related increases in instability
were observed as increased incongruity magnitude and trial-to-trial variability
during the two rapid stepping conditions, relative to preferred speed stepping.
Our findings suggest that increased COM incongruity and trial-to-trial
variability among older adults signify a reduction in dynamic stability, which
may arise from difficulty in reactive control during the restabilisation phase.
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Langue : ANGLAIS