Document Detail


Is there evidence for nonthermal modulation of whole body heat loss during intermittent exercise?
MedLine Citation:
PMID:  20445158     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
This study compared the effect of active, passive, and inactive recoveries on whole body evaporative and dry heat loss responses during intermittent exercise at an air temperature of 30 degrees C and a relative humidity of 20%. Nine males performed three 15-min bouts of upright seated cycling at a fixed external workload of 150 W. The exercise bouts were separated by three 15-min recoveries during which participants 1) performed loadless pedaling (active recovery), 2) had their lower limbs passively compressed with inflatable sleeves (passive recovery), or 3) remained upright seated on the cycle ergometer (inactive recovery). Combined direct and indirect calorimetry was employed to measure rates of whole body evaporative heat loss (EHL) and metabolic heat production (M-W). Mean body temperature (T(b)) was calculated from esophageal and mean skin temperatures, and mean arterial pressure (MAP) was measured continuously. Active and passive recoveries both reversed the reduction in MAP associated with inactive recovery (P <or= 0.05). This response was paralleled by greater levels of EHL during active (207 +/- 53 W) and passive recoveries (203 +/- 55 W) compared with the inactive condition (168 +/- 53 W, P <or= 0.05). However, the greater rate of EHL during active recovery was paralleled by a greater M-W (194 +/- 16 W) compared with inactive recovery (149 +/- 27 W, P <or= 0.001). In contrast, M-W during passive recovery (139 +/- 20 W) was not significantly different from the inactive condition (P = 0.468). Furthermore, there were no differences in T(b) between inactive and passive conditions during the recovery periods (P = 0.820). As such, passive recovery resulted in greater levels of EHL for a given change in T(b) compared with inactive recovery (P <or= 0.05). These results strongly suggest that the progressive increase in core temperature during successive exercise/rest cycles is primarily the result of a baroreflex-mediated attenuation of postexercise whole body evaporative heat loss.
Authors:
Glen P Kenny; Daniel Gagnon
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-05-05
Journal Detail:
Title:  American journal of physiology. Regulatory, integrative and comparative physiology     Volume:  299     ISSN:  1522-1490     ISO Abbreviation:  Am. J. Physiol. Regul. Integr. Comp. Physiol.     Publication Date:  2010 Jul 
Date Detail:
Created Date:  2010-06-25     Completed Date:  2010-07-08     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100901230     Medline TA:  Am J Physiol Regul Integr Comp Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  R119-28     Citation Subset:  IM    
Affiliation:
Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada. gkenny@uottawa.ca
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MeSH Terms
Descriptor/Qualifier:
Adult
Baroreflex
Body Temperature / physiology
Body Temperature Regulation / physiology*
Calorimetry, Indirect
Exercise / physiology*
Humans
Male
Rest / physiology
Skin Temperature
Temperature
Thermogenesis / physiology

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


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