Document Detail

Exercise-Associated Hyponatremia and Hydration Status in 161-km Ultramarathoners.
MedLine Citation:
PMID:  23135369     Owner:  NLM     Status:  Publisher    
PURPOSE: This work combines and reanalyzes five years of exercise-associated hyponatremia (EAH) research at 161-km ultramarathons in northern California with primary purposes to define the relationship between post-race blood sodium concentration ([Na]) and change in body weight, examine the interactions among EAH incidence, ambient temperature and hydration state, and explore the effect of hydration status on performance. METHODS: Pre-race and post-race body weight and finish time data were obtained on 887 finishers, and post-race [Na] was also obtained on a subset of 669 finishers. RESULTS: EAH incidence was 15.1% overall (range 4.6- 51.0% by year) and had a significant positive relationship with ambient temperature. Of the runners with EAH, 23.8% were classified as overhydrated (weight change ≥0), 40.6% were euhydrated (weight change <0 to -3%), and 35.6% were dehydrated (weight change <-3%) at the finish. There was a weak significant relationship (r=0.17, p<0.0001) between post-race [Na] and change in body weight such that a lower [Na] was more common with increased weight loss. Considering all finishers examined, 18.5% were dehydrated and 34.9% were overhydrated at the finish. There was a weak significant relationship (r=0.092, p=0.006) between change in body weight and performance in that faster runners tended to lose more weight. Top finishers varied in body weight change from ~1% gain to ~6% loss. CONCLUSION: EAH incidence can be high in 161-km ultramarathons in northern California. In this environment, EAH is more common with dehydration than overhydration and is more common in hotter ambient temperature conditions. Because weight loss >3% does not appear to have an adverse effect on performance, excessive sodium supplementation and aggressive fluid ingestion beyond the dictates of thirst are ill-advised.
Martin D Hoffman; Tamara Hew-Butler; Kristin J Stuempfle
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-11-6
Journal Detail:
Title:  Medicine and science in sports and exercise     Volume:  -     ISSN:  1530-0315     ISO Abbreviation:  Med Sci Sports Exerc     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-11-8     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8005433     Medline TA:  Med Sci Sports Exerc     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1Department of Physical Medicine & Rehabilitation, Department of Veterans Affairs, Northern California Health Care System, and University of California Davis Medical Center, Sacramento, CA, United States 2Exercise Science Program, Oakland University, Rochester, MI, United States 3Health Sciences Department, Gettysburg College, Gettysburg, PA, United States.
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