Document Detail


'Cross-adaptation': habituation to short repeated cold-water immersions affects the response to acute hypoxia in humans.
MedLine Citation:
PMID:  20643773     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Adaptation to an environmental stressor is usually studied in isolation, yet these stressors are often encountered in combination in the field, an example being cold and hypoxia at altitude. There has been a paucity of research in this area, although work with rodents indicates that habituation to repeated short cold exposures has a cross-adaptive effect during hypoxia. The present study tested the hypothesis that cross-adaptation is also possible with humans. Thirty-two male volunteers were exposed to 10 min bouts of normoxic and hypoxic (FIO2 0.12) rest and exercise (100 W on a recumbent cycle ergometer). These were repeated after a 96 h interval, during which participants completed six, 5 min immersions in either cold (12°C, CW) or thermoneutral water (35°C, TW). Venous blood samples were taken immediately after each bout, for determination of catecholamine concentrations. A three-lead ECG was recorded throughout and the final 5 min of each bout was analysed for heart rate variability using fast fourier transformations (and displayed as log transformed data (ln)). In comparison with the first hypoxic exercise exposure, the second exposure of the CW group resulted in an increased ln high frequency (ln HF) power (P < 0.001) and reduced adrenaline (P < 0.001) and noradrenaline concentrations (P < 0.001). Adrenaline and noradrenaline concentrations were lower in the CW group during the second hypoxic exercise compared to the TW group (P = 0.042 and P = 0.003), but ln HF was not. When separated into hypoxic sensitive and hypoxic insensitive subgroups, ln HF was higher in the hypoxic sensitive CW group during the second hypoxic exercise than in any of the other subgroups. Cold habituation reduced the sympathetic response (indicated by the reduced catecholamine concentrations) and elevated the parasympathetic activity (increased ln HF power) to hypoxic exercise. These data suggest a generic autonomic cross-adaptive effect between cold habituation and exposure to acute hypoxia in humans.
Authors:
Heather C Lunt; Martin J Barwood; Jo Corbett; Michael J Tipton
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-07-19
Journal Detail:
Title:  The Journal of physiology     Volume:  588     ISSN:  1469-7793     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  2010 Sep 
Date Detail:
Created Date:  2010-09-16     Completed Date:  2011-01-19     Revised Date:  2013-05-29    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  3605-13     Citation Subset:  IM    
Affiliation:
Department of Sport and Exercise Science, University of Portsmouth, Cambridge Road, Portsmouth PO1 2ER, UK. heather.lunt@port.ac.uk
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MeSH Terms
Descriptor/Qualifier:
Adaptation, Physiological / physiology*
Anoxia / metabolism*
Cold Temperature*
Heart Rate*
Humans
Immersion / physiopathology*
Male
Respiratory Mechanics / physiology
Skin Temperature / physiology
Sympathetic Nervous System / physiology
Comments/Corrections

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


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