Document Detail

Compliant characteristics of single joints: preservation of equifinality with phasic reactions.
MedLine Citation:
PMID:  2310787     Owner:  NLM     Status:  MEDLINE    
Electromyograms (EMGs) of elbow flexors and extensors, elbow joint angle and torque were recorded in healthy subjects in the "do not react voluntarily" paradigm. Random loading and unloading torque perturbations of different rise times (Tr) were applied. Perturbations with Tr less than 300 ms evoke a phasic increase (in case of loading) or decrease (in case of unloading) in the flexor EMGs. The shortest EMG latency of about 30 ms was observed with very rapid perturbations (Tr less or equal to 20 ms). Smooth torque changes (Tr of 500-800 ms) were not accompanied by noticeable phasic reactions. Two types of the compliant characteristics were recorded: those with a zone of relatively high stiffness at the starting point ("S-shaped" curves) and those with a relatively constant stiffness. The presence or absence of the S-shape does not depend on Tr and therefore, does not seem to depend on phasic reflex or triggered reactions. In some of the subjects who were tested twice with an intervals of 2 months, the form of the compliant characteristics changed. This finding suggests that presence or absence of the S-shape can depend upon the subject's ability to follow the "do not react voluntarily" instruction. The invariance of the compliant characteristics in the presence or absence of reflex reactions can be regarded as an example of equifinality in a case of transient perturbations generated within the motor control system.
M L Latash; G L Gottlieb
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Biological cybernetics     Volume:  62     ISSN:  0340-1200     ISO Abbreviation:  Biol Cybern     Publication Date:  1990  
Date Detail:
Created Date:  1990-04-25     Completed Date:  1990-04-25     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  7502533     Medline TA:  Biol Cybern     Country:  GERMANY, WEST    
Other Details:
Languages:  eng     Pagination:  331-6     Citation Subset:  IM    
Department of Neurosurgery, Rush Medical College, Chicago, IL 60612.
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MeSH Terms
Elbow Joint / physiology*
Muscles / physiology*
Grant Support

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