Document Detail


The convective afterdrop component during hypothermic exercise decreases with delayed exercise onset.
MedLine Citation:
PMID:  9451529     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
HYPOTHESIS: Following cold water immersion, the post-cooling decrease in esophageal temperature (Tes) (i.e., afterdrop) is 3 times greater during exercise than during shivering, presumably due to increased muscular blood flow and convective core-to-periphery heat loss with exercise (J. Appl. Physiol. 63:2375, 1987). We felt that if exercise were to commence once the afterdrop period during shivering is complete, the threat of a further decrease in Tes (i.e., a second afterdrop) during the subsequent exercise would be minimized because much of the convective capacity for core cooling would already be dissipated. METHODS: Six subjects were each cooled three times in 8 degrees C water, until Tes decreased to 35.3 +/- 0.7 degrees C, and rewarmed by either shivering alone, exercise, or exercise commencing once a shivering afterdrop period was complete. RESULTS: The initial afterdrop was greater during Exercise only (1.1 +/- 0.4 degrees C) than Shivering only (0.35 +/- 0.3 degrees C) and Shivering-Exercise (0.45 +/- 0.2 degrees C) (p < 0.05). In contrast, exercise caused a secondary afterdrop of only 0.38 +/- 0.3 degrees C during Shivering-Exercise (p < 0.05). The initial rewarming rate during Exercise only (3.45 degrees C.h-1) was greater than the initial (2.7 degrees C.h-1) and second (2.4 degrees C.h-1) rewarming rates during Shivering-Exercise (p < 0.05), but not significantly greater than during Shivering only (2.99 degrees C.h-1) (p < 0.1). DISCUSSION: It is likely that during the Shivering-Exercise protocol, continued blood flow to shivering muscles: a) contributes to the initial afterdrop, and thus b) diminishes the convective capacity (or heat sink) available for further cooling during subsequent exercise.
Authors:
G G Giesbrecht; G K Bristow
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Aviation, space, and environmental medicine     Volume:  69     ISSN:  0095-6562     ISO Abbreviation:  Aviat Space Environ Med     Publication Date:  1998 Jan 
Date Detail:
Created Date:  1998-03-04     Completed Date:  1998-03-04     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7501714     Medline TA:  Aviat Space Environ Med     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  17-22     Citation Subset:  IM; S    
Affiliation:
Laboratory for Exercise and Environmental Medicine, Health, Leisure and Human Performance Research Institute, Faulty of Physical Education and Recreation Studies, Manitoba, Canada.
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MeSH Terms
Descriptor/Qualifier:
Adult
Body Composition
Body Height
Body Temperature / physiology*
Body Weight
Convection*
Esophagus / physiopathology*
Exercise / physiology*
Exercise Test
Female
Humans
Hypothermia / etiology,  physiopathology*
Immersion / adverse effects*
Male
Rewarming / methods*
Shivering / physiology*
Skinfold Thickness
Time Factors

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


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