Abstract
Objective
To systematically characterize the effect of flexion synergy expression on the manifestation
of elbow flexor stretch reflexes poststroke, and to relate these findings to elbow
flexor stretch reflexes in individuals without neurologic injury.
Design
Controlled cohort study.
Setting
Academic medical center.
Participants
Participants (N=20) included individuals with chronic hemiparetic stroke (n=10) and
a convenience sample of individuals without neurologic or musculoskeletal injury (n=10).
Interventions
Participants with stroke were interfaced with a robotic device that precisely manipulated
flexion synergy expression (by regulating shoulder abduction loading) while delivering
controlled elbow extension perturbations over a wide range of velocities. This device
was also used to elicit elbow flexor stretch reflexes during volitional elbow flexor
activation, both in the cohort of individuals with stroke and in a control cohort.
In both cases, the amplitude of volitional elbow flexor preactivation was matched
to that generated involuntarily during flexion synergy expression.
Main Outcome Measures
The amplitude of short- and long-latency stretch reflexes in the biceps brachii, assessed
by electromyography, and expressed as a function of background muscle activation and
stretch velocity.
Results
Increased shoulder abduction loading potentiated elbow flexor stretch reflexes via
flexion synergy expression in the paretic arm. Compared with stretch reflexes in individuals
without neurologic injury, paretic reflexes were larger at rest but were approximately
equal to control muscles at matched levels of preactivation.
Conclusions
Because flexion synergy expression modifies stretch reflexes in involved muscles,
interventions that reduce flexion synergy expression may confer the added benefit
of reducing spasticity during functional use of the arm.
Keywords
List of abbreviations:
BIC (biceps), EE (elbow extension), EF (elbow flexion), LLR (long-latency reflex), MVT (maximum voluntary torque), SABD (shoulder abduction), SLR (short-latency reflex)To read this article in full you will need to make a payment
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Article info
Publication history
Published online: July 24, 2017
Footnotes
Current affiliation for McPherson, Department of Biomedical Engineering, Florida International University, Miami, FL.
Supported by the National Institutes of Health (grant nos. R01-HD039343 and R01-NS054269) and the American Heart Association (award no. 10POST2790017).
Disclosures: none.
Identification
Copyright
© 2017 by the American Congress of Rehabilitation Medicine
