Document Detail

Acute effects of dehydration on sweat composition in men during prolonged exercise in the heat.
MedLine Citation:
PMID:  15329055     Owner:  NLM     Status:  MEDLINE    
AIM: To determine whether acute exercise-heat-induced dehydration affects sweat composition, eight males cycled for 2 h at 39.5 +/- 1.6% VO2peak on two separate occasions in a hot-humid environment (38.0 +/- 0.0 degrees C, 60.0 +/- 0.1% relative humidity). METHODS: During exercise, subjects ingested either no fluid (dehydration) or a 20 mmol L(-1) sodium chloride solution (euhydration). The volume of solution, calculated from whole-body sweat loss and determined in a familiarization trial, was ingested at 0 min and every 15 min thereafter. Venous blood was collected at 0, 60 and 120 min of exercise and sweat was aspirated from a patch located on the dominant forearm at 120 min. RESULTS: Following the 2-h cycling exercise, sweat [Na+] and [Cl-] was greater (P < 0.05) in the dehydration trial (Na+ 91.1 +/- 6.8 mmol L(-1); Cl- 73.3 +/- 3.5 mmol L(-1)) compared with the euhydration trial (Na+ 81.1 +/- 5.9 mmol L(-1); Cl- 68.5 +/- 3.3 mmol L(-1)). In addition, dehydration invoked a greater serum [Na+] (142.2 +/- 0.7 mmol L(-1); P < 0.05), [Cl-] (105.8 +/- 0.6 mmol L(-1); P < 0.05) and [K+] (5.27 +/- 0.2 mmol L(-1); P < 0.05) over the euhydration values for [Na+], [Cl-] and [K+], respectively (138.9 +/- 0.6, 102.9 +/- 0.5 and 4.88 +/- 0.1 mmol L(-1)). Plasma aldosterone was also significantly higher during exercise in the dehydration trial compared with the euhydration trial (53.8 +/- 3.8 vs. 40.0 +/- 4.3 ng dL(-1); P < 0.05). CONCLUSIONS: Acute exercise-heat stress without fluid replacement resulted in a greater sweat [Na+] and [Cl-] which was potentially related to greater extracellular fluid [Na+], plasma aldosterone or sympathetic nervous activity.
R M Morgan; M J Patterson; M A Nimmo
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Acta physiologica Scandinavica     Volume:  182     ISSN:  0001-6772     ISO Abbreviation:  Acta Physiol. Scand.     Publication Date:  2004 Sep 
Date Detail:
Created Date:  2004-08-26     Completed Date:  2004-12-20     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0370362     Medline TA:  Acta Physiol Scand     Country:  England    
Other Details:
Languages:  eng     Pagination:  37-43     Citation Subset:  IM    
Strathclyde Institute for Biomedical Sciences, University of Strathclyde, Glasgow, UK.
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MeSH Terms
Aldosterone / blood
Body Temperature Regulation / physiology
Chlorides / analysis,  blood
Dehydration / physiopathology*
Exercise / physiology*
Hot Temperature*
Hydrogen-Ion Concentration
Potassium / analysis,  blood
Sodium / analysis,  blood
Sweat / chemistry,  physiology*
Reg. No./Substance:
0/Chlorides; 52-39-1/Aldosterone; 7440-09-7/Potassium; 7440-23-5/Sodium

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