Document Detail

Autonomic nervous control of the heart rate during isometric exercise in normal man.
MedLine Citation:
PMID:  3562205     Owner:  NLM     Status:  MEDLINE    
The relative contribution of the efferent components of the autonomic nervous system to the regulation of tachycardia induced by isometric exercise was assessed in 23 normal males. The isometric exercise (handgrip) was performed at the maximum intensity tolerated by the individual over a period of 10 s (maximal voluntary contraction-MVC) and at levels equivalent to 75, 50 and 25% of MVC for 20, 40 and 10 s, respectively. The study was performed both under control conditions and after pharmacological blockade with atropine (12 individuals) or propranolol (11 individuals). Under control conditions, the heart rate (HR) responses to isometric effort were dependent on the intensity and duration of the exercise, showing a tendency towards progressive elevation with the maintenance of muscular contraction at the levels studied. The tachycardia evoked by this effort was of considerable magnitude and of rapid onset, especially at the more intense levels of activity. Parasympathetic blockade markedly decreased tachycardia, which manifested itself during the first 10 s of exercise at all levels of intensity, whereas sympathetic blockade markedly modified the HR response after 10 s of effort at the 75 and 50% MVC levels. A slight depression of the tachycardiac response could be observed already after 10 s of maximum effort after propranolol. The present results suggest that the autonomic regulation of these responses is based on a biphasic mechanism, with the initial phase depending on the rapid withdrawal of the parasympathetic influence, followed by a marked sympathetic contribution to the induction of tachycardia after 10 s of isometric contraction or even a little before at maximum exertion.
B C Maciel; L Gallo Júnior; J A Marin Neto; L E Martins
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Pflügers Archiv : European journal of physiology     Volume:  408     ISSN:  0031-6768     ISO Abbreviation:  Pflugers Arch.     Publication Date:  1987 Feb 
Date Detail:
Created Date:  1987-05-12     Completed Date:  1987-05-12     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  0154720     Medline TA:  Pflugers Arch     Country:  GERMANY, WEST    
Other Details:
Languages:  eng     Pagination:  173-7     Citation Subset:  IM    
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MeSH Terms
Atropine / pharmacology
Autonomic Nervous System / physiology*
Heart Rate*
Isometric Contraction*
Muscle Contraction*
Parasympathetic Nervous System / physiology
Propranolol / pharmacology
Sympathetic Nervous System / physiology
Reg. No./Substance:
51-55-8/Atropine; 525-66-6/Propranolol

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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