  Due to hemiparesis, stroke survivors frequently develop a dysfunctional gait
that is often characterized by an overall decrease in walking speed and a
unilateral decrease in step length. With millions currently affected by this
dysfunctional gait, robust and effective rehabilitation protocols are needed.
Although robotic devices have been used in numerous rehabilitation protocols
for gait, the lack of significant aftereffects that translate to effective
therapy makes their application still questionable. This paper proposes a novel
type of robot-assisted intervention that results in significant aftereffects
that last much longer than any other previous study. With the utilization of a
novel robotic device, the Variable Stiffness Treadmill (VST), the stiffness of
the walking surface underneath one leg is decreased for a number of steps. This
unilateral stiffness perturbation results in a significant aftereffect that is
both useful for stroke rehabilitation and often lasts for over 200 gait cycles
after the intervention has concluded. More specifically, the aftereffect
created is an increase in both left and right step lengths, with the
unperturbed step length increasing significantly more than the perturbed. These
effects may be helpful in correcting two of the most common issues in
post-stroke gait: overall decrease in walking speed and a unilateral shortened
step length. The results of this work show that a robot-assisted therapy
protocol involving repeated unilateral stiffness perturbations can lead to a
more permanent and effective solution to post-stroke gait.
