Absence of stretch reflex gain enhancement in voluntarily activated spastic muscle

Wynne A. Lee; Ann Boughton; William Z. Rymer

doi:10.1016/0014-4886(87)90245-7

Absence of stretch reflex gain enhancement in voluntarily activated spastic muscle

Wynne A. Lee, Ann Boughton, William Z. Rymer^*

^*Corresponding author for this work

Physical Medicine and Rehabilitation

Research output: Contribution to journal › Article › peer-review

100 Scopus citations

Abstract

Static and dynamic stiffnesses of voluntarily activated elbow muscles were compared in spastic and contralateral arms of 15 subjects with spastic hemiparesis. Stiffnesses were estimated from the positional deflections induced by applying load perturbations to each forearm. In 11 15 subjects (73%), stiffnesses were comparable on the two sides. In the remaining 4 15 subjects (27%), stiffnesses were consistently greater on the spastic side, however, EMG recordings from these spastic muscles were of much smaller amplitude than those of the contralateral muscles, indicating that this increase was probably caused by changes in the mechanical properties of elbow muscles, rather than by stretch reflex enhancement. We conclude that for voluntarily activated muscles of spastic hemiparetic subjects, reflex stiffness (and presumably stretch reflex gain), of spastic and contralateral limbs is not significantly different. These findings impose important constraints upon theories attempting to explain spastic hypertonia, and they also provide guidelines for clinical quantification of spasticity.

Original language	English (US)
Pages (from-to)	317-335
Number of pages	19
Journal	Experimental Neurology
Volume	98
Issue number	2
DOIs	https://doi.org/10.1016/0014-4886(87)90245-7
State	Published - Nov 1987

Funding

’ The authors are grateful to the staff of the Rehabilitation Institute of Chicago for referring their patients. Special thanks are offered to Dr. W. A. Adair, Dr. P. Kaplan, Dr. M. Kim, Dr. S. Lal, Dr. W. Nimmer, Dr. V. Sahgal, and Dr. Y. Wu. The research described was supported by NIH grant NS 19331, NIHR grant GO08300079 (W.Z.R.) and by the Coleman, Hearst, J. M. Joyce, Regenstein, and Searle Foundations. W.A.L.‘s current affiliation is Programs in Physical Therapy, Northwestern University Medical School. Please address correspondence to Dr. W. Z. Rymer, Department of Physiology, Ward 5-295, Northwestern University Medical School, 303 East Chicago Av., Chicago, IL 606 11.

ASJC Scopus subject areas

Neurology
Developmental Neuroscience

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title = "Absence of stretch reflex gain enhancement in voluntarily activated spastic muscle",

abstract = "Static and dynamic stiffnesses of voluntarily activated elbow muscles were compared in spastic and contralateral arms of 15 subjects with spastic hemiparesis. Stiffnesses were estimated from the positional deflections induced by applying load perturbations to each forearm. In 11 15 subjects (73%), stiffnesses were comparable on the two sides. In the remaining 4 15 subjects (27%), stiffnesses were consistently greater on the spastic side, however, EMG recordings from these spastic muscles were of much smaller amplitude than those of the contralateral muscles, indicating that this increase was probably caused by changes in the mechanical properties of elbow muscles, rather than by stretch reflex enhancement. We conclude that for voluntarily activated muscles of spastic hemiparetic subjects, reflex stiffness (and presumably stretch reflex gain), of spastic and contralateral limbs is not significantly different. These findings impose important constraints upon theories attempting to explain spastic hypertonia, and they also provide guidelines for clinical quantification of spasticity.",

author = "Lee, {Wynne A.} and Ann Boughton and Rymer, {William Z.}",

note = "Funding Information: {\textquoteright} The authors are grateful to the staff of the Rehabilitation Institute of Chicago for referring their patients. Special thanks are offered to Dr. W. A. Adair, Dr. P. Kaplan, Dr. M. Kim, Dr. S. Lal, Dr. W. Nimmer, Dr. V. Sahgal, and Dr. Y. Wu. The research described was supported by NIH grant NS 19331, NIHR grant GO08300079 (W.Z.R.) and by the Coleman, Hearst, J. M. Joyce, Regenstein, and Searle Foundations. W.A.L.{\textquoteleft}s current affiliation is Programs in Physical Therapy, Northwestern University Medical School. Please address correspondence to Dr. W. Z. Rymer, Department of Physiology, Ward 5-295, Northwestern University Medical School, 303 East Chicago Av., Chicago, IL 606 11.",

year = "1987",

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doi = "10.1016/0014-4886(87)90245-7",

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AU - Boughton, Ann

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PY - 1987/11

Y1 - 1987/11

N2 - Static and dynamic stiffnesses of voluntarily activated elbow muscles were compared in spastic and contralateral arms of 15 subjects with spastic hemiparesis. Stiffnesses were estimated from the positional deflections induced by applying load perturbations to each forearm. In 11 15 subjects (73%), stiffnesses were comparable on the two sides. In the remaining 4 15 subjects (27%), stiffnesses were consistently greater on the spastic side, however, EMG recordings from these spastic muscles were of much smaller amplitude than those of the contralateral muscles, indicating that this increase was probably caused by changes in the mechanical properties of elbow muscles, rather than by stretch reflex enhancement. We conclude that for voluntarily activated muscles of spastic hemiparetic subjects, reflex stiffness (and presumably stretch reflex gain), of spastic and contralateral limbs is not significantly different. These findings impose important constraints upon theories attempting to explain spastic hypertonia, and they also provide guidelines for clinical quantification of spasticity.

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Absence of stretch reflex gain enhancement in voluntarily activated spastic muscle

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