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Br J Sports Med. 2007 August; 41(8): 496.
PMCID: PMC2465430

Commentary

In addition to their primary finding that ibuprofen use was not associated with decreased plasma sodium concentration ([Na+]p, mmol/l), the authors found that there was no relationship between post‐race [Na+]p and weight change. Every other study to date1,2,3 (Noakes et al1 cites all previous studies) “in which pre‐ and post‐event [Na+]p have been measured [has found that] the more an athlete weighs at the end of an event compared with his/her weight at the start, the lower is the [Na+]p”.4 Thus, the authors' conclusion that “weight gain by itself does not put an individual at risk for hyponatremia” is consistent only with their own anomalous finding.

Among possible reasons for the authors' anomalous result is the Western States 100 Mile Endurance Run's long‐standing mandatory weight check policy,5 unique among events thus far studied. A culture of weighing‐in light has developed6 because this policy has, until very recently, been directed at weight loss only. Runners weigh in the day before the race, and common practice is to do so before breakfast, in a somewhat dehydrated state. If the subjects in the present study were not exempt from the race's weight check policy, it is possible that their pre‐race weights were misleadingly low, and resulted in weight change estimates erroneously skewed in the direction of weight gain.

References

1. Noakes T D, Sharwood K, Speedy D. et al Three independent biological mechanisms cause exercise‐associated hyponatremia: evidence from 2,135 weighed competitive athletic performances. Proc Natl Acad Sci USA 2005. 10218550–18555.18555 [PubMed]
2. Page A J, Reid S A, Speedy D B. et al Exercise‐associated hyponatremia, renal function, and nonsteroidal antiinflammatory drug use in an ultraendurance mountain run. Clin J Sport Med 2007. 1743–48.48 [PubMed]
3. Hew‐Butler T, Bosch A, Sharwood K. et al Maintenance of plasma volume and serum sodium concentration despite body weight loss in Ironman athletes. Clin J Sport Med 2007. 17116–122.122 [PubMed]
4. Weschler L B. Exercise‐associated hyponatraemia: a mathematical review. Sports Med 2005. 35899–922.922 [PubMed]
5. Western States 100 Mile Endurance Run. http: ws100, com/pguide. htm#vii (accessed 14 May 2007)
6. Glace B W, Murphy C A, McHugh M P. Food intake and electrolyte status of ultramarathoners competing in extreme heat. J Am Coll Nutr 2002. 21553–559.559 [PubMed]

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