Background.
The residual hemiparesis after stroke results in a unilateral reduction
in propulsive force during gait. Prior work has suggested the presence
of a propulsive reserve in the paretic limb. Objective. The
purpose of this study was to quantify the paretic propulsive reserve in
individuals poststroke and to determine the biomechanical mechanism
underlying the generation of additional paretic propulsive limb force.
Methods.
Ten individuals with chronic hemiparesis poststroke walked on a
treadmill
(What type?
against an impeding force (ascending 0% to 10% body weight
[BW], in 2.5% BW increments, followed by descending 10% to 0% BW, also
in 2.5% BW increments) applied to the body’s center of mass. The
resulting propulsive forces were measured bilaterally and compared
between impeding force levels. We then assessed potential mechanisms
(trailing limb angle and plantarflexion moment) underlying the changes
in propulsion.
Results. Overall, peak paretic propulsive force
increased by 92% and the paretic propulsive impulse increased by 225%,
resulting in a significant increase in the paretic limb’s contribution
to propulsion. Participants continued to produce increased paretic
propulsion on removal of the impeding force. The trailing limb angle
contributed significantly to the increase in paretic propulsion, whereas
the plantarflexion moment did not.
Conclusions. Participants
exhibited a robust propulsive reserve on the paretic limb, suggesting
that there is untapped potential that can be exploited through
rehabilitation to improve gait recovery. The increase in propulsive
symmetry indicates that a greater response was observed by the paretic
limb rather than increased compensation by the nonparetic limb.
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