Comparison Of Changes in Gait Biomechanics and Neuromotor Excitability Induced by Ambulation Training with and Without Functional Electrical Stimulation
Author(s)
Spencer, Jacob
Advisor(s)
Kesar, Trisha
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Abstract
Functional electrical stimulation (FES) involves the use of electrical stimulation to facilitate or augment functional movements such as reaching or gait. FES is commonly used as a standalone or adjunctive treatment tool during rehabilitation of a diverse array of neuro-pathologies, including stroke, traumatic brain injury, and multiple sclerosis. Despite the popularity of FES in clinical practice, as well as strong evidence supporting its orthotic (i.e. immediate) and therapeutic (i.e. long-term) benefits, there are still outstanding questions concerning the potential neural mechanisms of action of FES. Because FES is often used to supplement other interventions, such as overground or treadmill-based gait training, which can independently elicit changes in neuromotor excitability, there is a need to understand the individual and synergistic effects of FES on neuromotor circuitry. This thesis summarizes the results of two studies designed to further our scientific understanding of the neural mechanisms underlying FES-assisted gait training. The purpose of the first study was to compare acute effects of 30 minutes of fast walking (Fast) and 30 minutes of fast walking with functional electrical stimulation of the ankle plantarflexors and dorsiflexors (FastFES) in 14 able-bodied young adults. Immediately before and after training, we evaluated corticomotor excitability measured using motor evoked potentials (MEPs) elicited in response to transcranial magnetic stimulation, monosynaptic spinal reflex excitability measured using Hoffman’s or H-reflexes, and propulsive force generation during gait measured by anterior ground reaction forces (AGRF). The purpose of the second study was to compare acute changes in corticomotor excitability measured by MEP amplitude, cortical inhibition measured by cortical silent period duration (CSP), and propulsive force generation during gait measured by AGRFs, induced by 30 minutes of Fast gait training versus 30 minutes of FastFES gait training in 16 individuals with chronic stroke. Our long-term goal is to combine measures of neuromotor excitability with measures of gait function, in order to illuminate the neural mechanisms underlying response to Fast and FastFES and identify baseline characteristics of potential responders and non-responders.
In our study of young able-bodied individuals, we observed an increase in test-side AGRF in the FastFES condition alone, as well as a reduction in MEP amplitude and H/M ratio across both conditions without a significant difference between conditions. In our study of post-stroke individuals, we observed an increase AGRF across both groups without a significant between group difference. Additionally, we observed an across groups decrease in MEP amplitude following training, and a decrease in CSP duration following the Fast group alone. While changes in AGRF in the stroke experiment did not differ significantly between groups, differences in CSP duration imply that changes in AGRF for each group may have been the result of different neurophysiological processes. If different neurophysiological substrates are responsible for Fast and FastFES, then it is possible that which intervention is most effective intervention may vary between individuals based on their baseline neuromotor function. This notion is further supported by our finding of a significant positive correlation between baseline MEP amplitude and intervention response in able-bodied individuals. The scope of the current study limited our ability to perform high-powered correlational analysis, but future research probing relationships between baseline functional and neurophysiological function and treatment response for Fast and FastFES are warranted. Furthermore, future research assessing bilateral neurophysiological responses to Fast and FastFES both acutely and longitudinal is warranted.
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Date
2025-02-26
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Text
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Dissertation