Document Detail

Ad libitum fluid replacement in military personnel during a 4-h route march.
MedLine Citation:
PMID:  20142772     Owner:  NLM     Status:  MEDLINE    
INTRODUCTION: Opportunities to determine optimal rates of fluid ingestion could reduce the mass soldiers might need to carry on military missions.
PURPOSE: The first objective was to evaluate the effects of an ad libitum fluid replacement strategy on total body water (TBW), core temperature, serum sodium concentrations [Na+], and plasma osmolality (POsm). The second objective was to determine if an ad libitum water intake was sufficient to maintain these variables during exercise. A third objective was to determine if changes in body mass are an accurate measure of changes in TBW.
METHODS: A field study was conducted with 15 soldiers performing a 16.4-km route march. The average age of 15 subjects was 27 yr (SD = 4.6 yr).
RESULTS: Their mean hourly ad libitum fluid intake was 383 mL (SD = 150 mL). Predicted sweat rate was 626 +/-122 mL.h-1. Despite an average body mass loss of 1.0 kg (SD = 0.50 kg) TBW, POsm and serum [Na+] did not change significantly during exercise. There was a significant (P < 0.05) linear relationship with a negative slope between postexercise serum [Na+] and changes in both body mass and percentage of TBW. Postexercise POsm and serum [Na+] were significantly related (P < 0.05). Higher postexercise percentage of TBW was associated with lower postexercise POsm and serum [Na+] levels. There was no relation between percent body mass loss and postexercise core temperature (38.1 degrees C +/- 0.6 degrees C).
CONCLUSIONS: A mean ad libitum water intake of 383 mL.h-1, replacing approximately 61% of body mass losses during 4 h of exercise, maintained TBW, core temperature, POsm, and serum [Na+] despite a 1.4% body mass loss. A reduction in body mass of 1.4% (1.0 kg) was not associated with a reduction in TBW.
Heinrich Nolte; Timothy D Noakes; Bernard Van Vuuren
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Medicine and science in sports and exercise     Volume:  42     ISSN:  1530-0315     ISO Abbreviation:  Med Sci Sports Exerc     Publication Date:  2010 Sep 
Date Detail:
Created Date:  2010-08-30     Completed Date:  2010-12-13     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8005433     Medline TA:  Med Sci Sports Exerc     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1675-80     Citation Subset:  IM; S    
ERGOnomics TECHnologies, Pretoria, South Africa.
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MeSH Terms
Body Temperature / physiology*
Body Water / physiology*
Drinking / physiology*
Exercise / physiology
Military Personnel*
Osmolar Concentration
Sodium / blood
Sweat / physiology
Weight Loss / physiology
Young Adult
Reg. No./Substance:

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

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