Abstract

To study disturbed muscle activation patterns in hemiparetic stroke, the EMG activity in spastic-paretic and contralateral elbow muscles of 10 stroke subjects were compared during graded directionally varying voluntary isometric contractions. We observed significant shifts in the peak EMG angle and increases in the angular range of EMG activity in the impaired upper limb. Furthermore, we observed stereotypic coactivation of many muscles acting at the same joint or at different joints across all subjects.

The effect of elbow angle changes on muscle coactivation patterns was studied by examining isometric torque-angle relations under passive and active conditions in 8 stroke subjects. Active torques were elicited voluntarily, or with electrical stimulation. Passive elastic stiffness was not significantly altered, however, shifts of torque-angle curves to more extended elbow positions were found in all but one subject during voluntary activation, but not during electrical stimulation. These results indicate the lack of significant alterations of muscle-tendon properties and may reflect differences in muscle coactivational strategies between the impaired and unimpaired elbow as a function of angle. Increases in muscle mechanoreceptor feedback due to alterations in flexor reflex interneuronal bias would also explain these observations.

The influence of cutaneous afferents on muscle coactivation patterns was studied in the upper limbs of 8 hemiparetic stroke subjects using electrical stimulation of the index finger of both the impaired and unimpaired upper limbs. In the unimpaired limb, shoulder muscle activity preceded elbow flexor activation in the unimpaired limb, under passive and active conditions, across all subjects. A more synchronized but delayed was observed in all muscles in the impaired limb. Furthermore, the unimpaired limb produced shoulder extension-retraction followed by elbow flexion, while only the elbow flexion response was present for the impaired limb. Obligatory coupling between certain elbow and shoulder muscles were observed in the impaired limb similar to those observed under voluntary activation conditions.

The obligatory muscle coactivation patterns observed in these studies may be caused by changes in interneuronal bias, more specifically of the flexor reflex interneurons, due to a loss of dorsolateral descending input at the impaired side.

LLU Discipline

Physiology

Department

Physiology

School

Graduate School

First Advisor

George Maeda

Second Advisor

Ross W. Adey

Third Advisor

Murray E. Brandstater

Fourth Advisor

John W. Patrickson

Fifth Advisor

W. Zev Rymer

Degree Name

Doctor of Philosophy (PhD)

Degree Level

Ph.D.

Year Degree Awarded

1992

Date (Title Page)

12-1992

Language

English

Library of Congress/MESH Subject Headings

Hemiplegia -- physiopathology; Muscle Contraction -- physiopathology; Neurophysiology -- methods

Type

Dissertation

Page Count

x; 144

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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