Document Detail


Cerebral blood flow and metabolism during exercise: implications for fatigue.
MedLine Citation:
PMID:  17962575     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
During exercise: the Kety-Schmidt-determined cerebral blood flow (CBF) does not change because the jugular vein is collapsed in the upright position. In contrast, when CBF is evaluated by (133)Xe clearance, by flow in the internal carotid artery, or by flow velocity in basal cerebral arteries, a approximately 25% increase is detected with a parallel increase in metabolism. During activation, an increase in cerebral O(2) supply is required because there is no capillary recruitment within the brain and increased metabolism becomes dependent on an enhanced gradient for oxygen diffusion. During maximal whole body exercise, however, cerebral oxygenation decreases because of eventual arterial desaturation and marked hyperventilation-related hypocapnia of consequence for CBF. Reduced cerebral oxygenation affects recruitment of motor units, and supplemental O(2) enhances cerebral oxygenation and work capacity without effects on muscle oxygenation. Also, the work of breathing and the increasing temperature of the brain during exercise are of importance for the development of so-called central fatigue. During prolonged exercise, the perceived exertion is related to accumulation of ammonia in the brain, and data support the theory that glycogen depletion in astrocytes limits the ability of the brain to accelerate its metabolism during activation. The release of interleukin-6 from the brain when exercise is prolonged may represent a signaling pathway in matching the metabolic response of the brain. Preliminary data suggest a coupling between the circulatory and metabolic perturbations in the brain during strenuous exercise and the ability of the brain to access slow-twitch muscle fiber populations.
Authors:
Neils H Secher; Thomas Seifert; Johannes J Van Lieshout
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Review     Date:  2007-10-25
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  104     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2008 Jan 
Date Detail:
Created Date:  2008-01-16     Completed Date:  2008-02-28     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  306-14     Citation Subset:  IM    
Affiliation:
Department of Anesthesia, The Copenhagen Muscle Research Center, Rigshospitalet, Denmark. nhsecher@rh.regionh.dk
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MeSH Terms
Descriptor/Qualifier:
Ammonia / metabolism
Animals
Brain* / blood supply,  metabolism
Cerebrovascular Circulation*
Energy Metabolism
Exercise / physiology*
Glycogen / metabolism
Humans
Interleukin-6 / metabolism
Muscle Contraction*
Muscle Fatigue*
Muscle, Skeletal / metabolism*
Oxygen Consumption*
Chemical
Reg. No./Substance:
0/Interleukin-6; 7664-41-7/Ammonia; 9005-79-2/Glycogen

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


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