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Salt and fluid loading: effects on blood volume and exercise performance.
MedLine Citation:
PMID:  23075561     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
During prolonged exercise, fluid and salt losses through sweating reduce plasma volume which leads to heart rate drift in association with hyperthermia and reductions in performance. Oral rehydration with water reduces the loss of plasma volume and lessens heart rate drift and hyperthermia. Moreover, the inclusion of sodium in the rehydration solution to levels that double those in sweat (i.e., around 90 mmol/l Na(+)) restores plasma volume when ingested during exercise, and expands plasma volume if ingested pre-exercise. Pre-exercise salt and fluid ingestion with the intention of expanding plasma volume has received an increasing amount of attention in the literature in recent years. In four studies, pre-exercise salt and fluid ingestion improved performance, measured as time to exhaustion, either during exercise in a thermoneutral or in a hot environment. While in a hot environment, the performance improvements were linked to lowering of core temperatures and heart rate, the reasons for the improved performance in a thermoneutral environment remain unclear. However, when ingesting pre-exercise saline solutions above 0.9% (i.e., > 164 mmol/l Na(+)), osmolality and plasma sodium increase and core temperature remain at dehydration levels. Thus, too much salt counteracts the beneficial effects of plasma volume expansion on heat dissipation and hence in performance. In summary, the available literature suggests that pre-exercise saline ingestion with concentrations not over 164 mmol/l Na(+) is an ergogenic aid for subsequent prolonged exercise in a warm or thermoneutral environment.
Authors:
Ricardo Mora-Rodriguez; Nassim Hamouti
Publication Detail:
Type:  Journal Article     Date:  2012-10-15
Journal Detail:
Title:  Medicine and sport science     Volume:  59     ISSN:  1662-2812     ISO Abbreviation:  Med Sport Sci     Publication Date:  2013  
Date Detail:
Created Date:  2012-10-18     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8402440     Medline TA:  Med Sport Sci     Country:  Switzerland    
Other Details:
Languages:  eng     Pagination:  113-9     Citation Subset:  IM    
Copyright Information:
Copyright © 2012 S. Karger AG, Basel.
Affiliation:
University of Castilla-La Mancha, Exercise Physiology Laboratory, Toledo, Spain.
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