All ETDs from UAB

Advisory Committee Chair

David A Brown

Advisory Committee Members

Christopher P Hurt

David M Morris

Steven A Kautz

Tapan S Mehta

Document Type

Dissertation

Date of Award

2018

Degree Name by School

Doctor of Philosophy (PhD) School of Health Professions

Abstract

Background: Inappropriate paretic-limb force generation is a hallmark of impaired walking function poststroke. In addition to weakness, the paretic limb misdirects foot forces during stance, which may be due to inappropriate postural influence over weakened locomotor control. Purpose: Investigate neural control interactions between posture and locomotor functions by manipulating postural influence during walking of nonimpaired and individuals poststroke. I present four studies investigating measures associated with locomotor function and foot-force direction under varying postural demands during walking. Methods: Study 1 compared comfortable walking speed (CWS) outcomes following two body-weight-support (BWS) training protocols for N=29 participants with chronic (≥5 months) poststroke hemiparesis and slow baseline CWS (<1.1 m/s). Study 2 tested the ability of a novel support apparatus to fully minimize postural demands of walking for N=20 nonimpaired participants. Study 3 used the support apparatus to characterize fore-aft (Fy) to vertical (Fz) ground reaction force (GRF) ratios (Fy/Fz ratios), joint moments, and muscle activity during propulsion of N = 16 nonimpaired participants walking at 1.0 and 0.5 m/s under 0 to 30% BWS versus within the support apparatus. Study 4 compared Fy/Fz ratios of N=17 individuals ≥ 6 months poststroke with residual hemiparesis at their CWS under 0 to 30% BWS versus within the support apparatus. Results: Study 1 showed significant pre-post improvement of CWS that, on average, did not reach the 0.16 m/s minimal clinically important difference regardless of intervention group. Study 2 showed that the support apparatus reduced trunk motion and negative mechanical work for nonimpaired individuals, and enabled matching of vertical GRFs to those of typical walking. Study 3 showed nonimpaired Fy/Fz ratios decreased across force targets while walking externally stabilized in the support apparatus, demonstrating a relative decoupling of fore-aft and vertical GRF components. Study 4 showed the paretic-limb Fy/Fz ratio was not better directed during externally stabilized walking in the support apparatus. Conclusions: Although nonimpaired individuals used intact locomotor control strategies when the support apparatus minimized postural demands, minimizing postural demands did not facilitate more appropriate paretic-limb foot-force direction. Individuals poststroke may rely on postural control mechanisms to compensate for loss of voluntary locomotor control.

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