Article

To ensure stability during gait, mediolateral placement of the swinging foot must
be actively regulated. Logically this occurs through end-point control of the
swing limb trajectory, the precision of which is quantified as step-width
variability (SWV). Increased SWV with age may reflect reduced precision of this
control, but cannot describe if, and how, age-related changes in lower limb
kinematic synergies account for reduced precision. We analyzed joint
configuration variance across steps within the uncontrolled manifold (UCM)
hypothesis, which assumes that redundant sets of elemental variables are
organized by the central nervous system to stabilize important performance
variables. We tested whether: (1) regardless of age, the swing limb trajectory
would be stabilized by a kinematic synergy of the lower limbs, and (2) the
strength of the synergy would be weaker in older adults. Ten younger and ten
older adults (65+ years) walked on a laboratory walkway at their preferred speed
while kinematic data were collected. UCM analysis of segmental configuration
variance was performed with respect to the mediolateral trajectory of the
swing-limb ankle joint center. Throughout most of swing, the trajectory was
stabilized by a kinematic synergy. Despite the greater segmental configuration
variance of older adults, the strength of the synergy was not significantly
different between groups. Moreover, the synergy index became negative during
terminal swing and was not significantly correlated with SWV. Accordingly,
co-variation among individual segmental trajectories is more important for
stabilization of the swing trajectory during mid-swing, and, throughout swing,
aging does not appear to affect this stabilization.
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Langue : ANGLAIS