Determining the effects of increased demands for voluntary adjustments on the neuromuscular control of walking post-stroke - Abstract
The goal of this proposal is to determine the effects of explicitly driven or implicitly driven walking modifications
on muscle activation patterns and co-contraction post-stroke. This work is significant, as studies have shown
that muscle activation patterns after neurologic injury cannot generate walking kinematics comparable to those
seen in neurotypical individuals; this finding implies that to attain true walking recovery after neurologic injury,
interventions should aim to restore the muscle activations underlying walking behaviors. Here, we first explore
muscle activations during walking using biofeedback to guide explicit modification of walking patterns, which is
a common approach used in clinical and research interventions for walking retraining. We hypothesize that
explicit walking modifications might be detrimental at a muscle activation level as they engage cortical
pathways for voluntary control that have been interrupted by the stroke lesion, resulting in increased muscle
co-contraction. Co-contraction hinders true recovery as it impairs the ability to selectively control different
segments during walking, resulting in overreliance on compensatory patterns. We will also explore muscle
activation patterns during implicit walking modifications. We will use external modifications in the walking
environment, mainly split-belt adaptation followed by tied belt walking, to assess if implicit modifications of
walking that rely less on cortical neural control are associated with levels of co-contraction comparable to
neurotypical controls—an indication that implicitly-mediated modifications could be a more effective approach
to restore muscle activation patterns during walking post-stroke. In this study, we will assess co-contraction
during walking in people post-stroke as they reduce asymmetry in step lengths guided by explicit biofeedback
(Aim 1) or implicitly following split-belt adaptation and washout (Aim 2). Our central hypothesis is that given
differences in the neural control of explicitly- vs. implicitly-mediated walking modifications, we will observe
greater levels of co-contraction with interventions that rely on explicit compared to implicit control.
Supplementing this central hypothesis, we also predict that co-contraction will be associated with motor
impairment, and in more impaired individuals co-contraction will be exacerbated by explicit modifications given
the reliance on lesioned cortical pathways. Our results will identify the tasks and conditions that can reduce co-
contraction to promote restoration of neuromuscular control post-stroke. This proposal aligns with the NCMRR
research priority to develop objective markers of treatment response and functional progress that predict
rehabilitation treatment response and enable the tailoring of interventions to the needs, abilities, and resources
of the person with disability.
