Document Detail


Cardiovascular responses to static and dynamic contraction during comparable workloads in humans.
MedLine Citation:
PMID:  12184989     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Previous studies suggest that the blood pressure response to static contraction is greater than that caused by dynamic exercise. In anesthetized cats, however, pressor responses to electrically induced static and dynamic contraction of the same muscle group are similar during equivalent workloads and peak tension development [i.e., similar tension-time index (TTI)]. To determine if the same relationship exists in humans, where contraction is voluntary and central command is present, dynamic (180 s; 1/s) and static (90 s) contractions at 30% of maximal voluntary contraction (MVC) were performed. Dynamic contraction also was repeated at the same TTI for 90 s at 60% MVC. Mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), MAP during postexercise arterial occlusion (an index of the metaboreceptor-induced activation of the exercise pressor reflex), and relative perceived exertion (RPE) (an index of central command) were assessed. No differences in these variables were found between static and dynamic contraction at a tension of 30% MVC. During dynamic contraction at 60% MVC, changes in MAP (16 +/- 3 vs. 19 +/- 4 mmHg) and absolute HR (92 +/- 6 vs. 69 +/- 5 beats/min), CO (7.9 +/- 0.4 vs. 6.3 +/- 0.3 l/min), RPE (16 +/- 1 vs. 13 +/- 1), and MAP during postexercise arterial occlusion (115 +/- 3 vs. 100 +/- 4 mmHg) were greater than during static contraction (P < 0.05). Thus increases in MAP and HR, activation of central command, and muscle metabolite-induced stimulation of the exercise pressor reflex during static and dynamic contraction in humans seem to be similar when peak tension and TTI are equal. Augmented responses to dynamic contraction at 60% MVC are likely related to greater activation of these two mechanisms.
Authors:
Charles L Stebbins; Buddy Walser; Mehrdad Jafarzadeh
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  American journal of physiology. Regulatory, integrative and comparative physiology     Volume:  283     ISSN:  0363-6119     ISO Abbreviation:  Am. J. Physiol. Regul. Integr. Comp. Physiol.     Publication Date:  2002 Sep 
Date Detail:
Created Date:  2002-08-19     Completed Date:  2002-09-19     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  100901230     Medline TA:  Am J Physiol Regul Integr Comp Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  R568-75     Citation Subset:  IM    
Affiliation:
Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616-8634, USA.
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MeSH Terms
Descriptor/Qualifier:
Adult
Blood Pressure / physiology
Brachial Artery / physiology
Cardiac Output / physiology
Female
Heart Rate / physiology
Hemodynamics / physiology*
Humans
Male
Middle Aged
Muscle Contraction / physiology*
Physical Exertion / physiology*
Reflex / physiology
Regional Blood Flow / physiology

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


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