Document Detail


Thermal and cardiovascular strain from hypohydration: influence of exercise intensity.
MedLine Citation:
PMID:  9562215     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
This study determined the effects of exercise intensity on the physiologic (thermal and cardiovascular) strain induced from hypohydration during heat stress. We hypothesized that the added thermal and cardiovascular strain induced by hypohydration would be greater during high intensity than low intensity exercise. Nine heat-acclimated men completed a matrix of nine trials: three exercise intensities, 25%, 45% and 65% VO2 max; and three hydration levels, euhydration and hypohydration at 3% and 5% body weight loss (BWL). During each trial, subjects attempted 50 min of treadmill exercise in a hot room (30 degrees C db, 50% rh) while body temperatures and cardiac output were measured. Hypohydration was achieved by exercise and fluid restriction the day preceding the trials. Core temperature increased (P<0.05) 0.12 degrees C per%BWL at each hypohydration level and was not affected by exercise intensity. Cardiac output was reduced (P<0.05) compared to euhydration levels and was reduced more during high compared to low intensity exercise after 5% BWL. It was concluded that: a) the thermal penalty (core temperature increase) accompanying hypohydration is not altered by exercise intensity; and b) at severe hypohydration levels, the cardiovascular penalty (cardiac output reduction) increases with exercise intensity.
Authors:
S J Montain; M N Sawka; W A Latzka; C R Valeri
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Publication Detail:
Type:  Comparative Study; Journal Article    
Journal Detail:
Title:  International journal of sports medicine     Volume:  19     ISSN:  0172-4622     ISO Abbreviation:  Int J Sports Med     Publication Date:  1998 Feb 
Date Detail:
Created Date:  1998-06-09     Completed Date:  1998-06-09     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  8008349     Medline TA:  Int J Sports Med     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  87-91     Citation Subset:  IM; S    
Affiliation:
Thermal & Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. smontain@natick-ccmail.army.mil
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MeSH Terms
Descriptor/Qualifier:
Acclimatization / physiology
Adult
Blood Volume / physiology
Body Temperature / physiology*
Body Temperature Regulation
Body Water / physiology
Body Weight
Cardiac Output / physiology*
Cardiac Output, Low / physiopathology
Dehydration / blood,  physiopathology*
Exercise Test
Heart Rate / physiology
Heat Stress Disorders / blood,  physiopathology
Hot Temperature / adverse effects
Humans
Male
Osmolar Concentration
Oxygen Consumption / physiology
Physical Exertion / physiology*
Stroke Volume / physiology

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


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