Award Date

5-1-2023

Degree Type

Doctoral Project

Degree Name

Doctor of Physical Therapy (DPT)

Department

Physical Therapy

First Committee Member

Jing Nong Liang

Second Committee Member

Daniel Young

Third Committee Member

Merrill Landers

Number of Pages

32

Abstract

Objective Transitioning from supported sitting position to standing activities requires coordinated interactions among postural muscles with appropriate reflexive responses to adapt to an increase in postural loading. Previous studies have found the failure to accommodate the challenge of increased postural loads in the stroke-impaired nervous system. In this study, we examined the H-reflex in response to different magnitudes of loads under static postural conditions, and compared the responses directly between individuals with a stroke-impaired nervous system and those with a non-neurologically impaired nervous system. We tested the hypothesis that the reflex amplitude would increase with increased load during standing in the non-neurologically impaired nervous system but would remain unchanged in the stroke-impaired nervous system. Methods Nine individuals with a history of stroke and thirteen healthy individuals each completed a reflex recording during static standing, under 3 loading conditions (1) -20% of body weight unloaded condition, (2) body weight condition, (3) +20% of body weight loaded condition. H-reflexes were elicited via electrical stimulation at the tibial nerve, and reflex responses were recorded on the soleus muscle. Results We observed increased H-reflex amplitudes under the weighted condition in controlled participants, compared to body weight and unweighted conditions. We observed a higher Hmax/Mmax ratio in the paretic leg regardless of loading conditions, which is in agreement with previous literature reporting higher H-reflex amplitudes in individuals with lesions in the central iv nervous system. In both paretic and non-paretic legs, we did not observe changes in H-reflex amplitudes with each loading condition. Conclusion Our findings suggest that an impaired ability to modulate the H-reflex pathway appropriately to increase the reflex stiffness of Ia afferent pathway, in response to changes in postural loads, may explain the reduced ability to adequately bear weight through lower limbs for standing, locomotion, and postural support tasks in individuals post-stroke. Significance The results of this study support the importance of early facilitation of weight-bearing activities with the incorporation of postural loading and unloading training, when considering clinical application for stroke recovery. Future studies will examine the adaptations of the Ia afferent pathway relative to postural loading during the subacute phases post-stroke, and its role during loaded and unloaded overground walking.

Keywords

H-Reflex; Post-Stroke; Spinal Circuit; Postural Load

Disciplines

Physical Therapy | Rehabilitation and Therapy

File Format

pdf

File Size

584 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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