Abstract
Changes
in the control of the lower extremities poststroke lead to persistent
biomechanical asymmetries during walking. These asymmetries are
associated with an increase in energetic cost, leading to the
possibility that reducing asymmetry can improve walking economy.
However, the influence of asymmetry on economy may depend on the
direction and cause of asymmetry. For example, impairments with paretic
limb advancement may result in shorter paretic steps, whereas deficits
in paretic support or propulsion result in shorter nonparetic steps.
Given differences in the underlying impairments responsible for step
length asymmetry, the capacity to reduce asymmetry and the associated
changes in energetic cost may not be consistent across this population.
Here, we identified factors explaining individual differences in the
capacity to voluntarily reduce step length asymmetry and modify
energetic cost during walking. A total of 24 individuals poststroke
walked on a treadmill, with visual feedback of their step lengths to aid
explicit modification of asymmetry. We found that individuals who took
longer paretic steps had a greater capacity to reduce asymmetry and were
better able to transfer the effects of practice to overground walking
than individuals who took shorter paretic steps. In addition, changes in
metabolic cost depended on the direction of asymmetry, baseline cost of
transport, and reductions in specific features of spatiotemporal
asymmetry. These results demonstrate that many stroke survivors retain
the residual capacity to voluntarily walk more symmetrically on a
treadmill and overground. However, whether reductions in asymmetry
reduce metabolic cost depends on individual differences in impairments
affecting locomotor function.
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