All ETDs from UAB

Advisory Committee Chair

David A Brown

Advisory Committee Members

Christopher P Hurt

Victor W Mark

Tapan S Mehta

Darcy Reisman

Document Type

Dissertation

Date of Award

2019

Degree Name by School

Doctor of Philosophy (PhD) School of Health Professions

Abstract

Background: Impaired paretic limb-loading dynamics and force-generation ability due to hemiparesis are partially responsible for permanent locomotor deficits poststroke. During walking, inability of the paretic limb to generate sufficient propulsive-forces causes reliance on compensatory strategies, wherein the nonparetic limb generates the majority of propulsive-forces needed for forward progression and speed modulation. Purpose: To investigate factors that can improve paretic limb propulsion and walking function, I present four studies. The first pertains to a protocol for a poststroke body-weight-support treadmill-training (BWSTT) study, while the others concern a mechanistic exploration of propulsive-force generation during walking against combined and differential FA resistance. Methods: Study 1 describes two 6-week challenge-based BWSTT paradigms for improving poststroke balance and walking speed (N=29). Study 2 utilized a novel robotic-split-treadmill interface to assess limb propulsion in nonimpaired individuals (N=17) targeting 1 m/s against combined FA resistance. Study 3 utilized the same walking environment to assess differences in relative interlimb propulsion in poststroke (N=21, walking at a target CWS inside device) and nonimpaired (N=15) against combined FA resistance. In study 4 we modified the interface environment to allow participants to control/drive speed of one belt while walking against FA resistance, while the other belt was set at a fixed speed and assessed limb propulsion during split-belt walking (2:1 speed ratio) in nonimpaired (N=15) and individuals poststroke (N=15). Results: In study 2 limb-propulsion proportionally increased with FA resistance applied, without affecting vertical forces. In study 3 against increasing levels of FA resistance, nonimpaired participants symmetrically and postroke participants asymmetrically increased interlimb propulsion with no change in relative propulsion between limbs. Study 4 nonimpaired participants selectively increased their slower-moving limb’s propulsion relative to the faster limb. Similarly, when the P limb moved slower against differential resistance it significantly increased its propulsion relative to the NP limb. Conclusions: These studies highlight that waking against increasing (combined/differential) FA resistance at a target speed encourages greater limb-propulsion possibly due to activation of limb-extensor mechanisms in both nonimpaired and poststroke individuals. Researchers and clinicians can apply these findings to design task specific poststroke gait interventions for improving paretic limb propulsion and participation during walking.

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