Three Independent Biological Mechanisms Cause Exercise-Associated Hyponatremia: Evidence from 2,135 Weighed Competitive Athletic Performances

To evaluate the role of fluid and Na+ balance in the development of exercise-associated hyponatremia (EAH), changes in serum Na+ concentrations ([Na+]) and in body weight were analyzed in 2,135 athletes in endurance events. Eighty-nine percent of athletes completed these events either euhydrated (39...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2005-12, Vol.102 (51), p.18550-18555
Main Authors: T. D. Noakes, K. Sharwood, D. Speedy, T. Hew, S. Reid, J. Dugas, C. Almond, P. Wharam, L. Weschler, Myers, Norman
Format: Article
Language:English
Subjects:
Athletes
Biological Sciences
Body Weight
Body weight changes
Dehydration
Exercise
Exercise - physiology
Fluids
Humans
Hyponatremia
Hyponatremia - blood
Hyponatremia - classification
Hyponatremia - etiology
Hyponatremia - physiopathology
Medical research
Racing
Secretion
Sodium
Sodium - blood
Sports - physiology
Weight gain
Weight loss
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Summary:To evaluate the role of fluid and Na+ balance in the development of exercise-associated hyponatremia (EAH), changes in serum Na+ concentrations ([Na+]) and in body weight were analyzed in 2,135 athletes in endurance events. Eighty-nine percent of athletes completed these events either euhydrated (39%) or with weight loss (50%) and with normal (80%) or elevated (13%) serum [Na+]. Of 231 (11%) athletes who gained weight during exercise, 70% were normonatremic or hypernatremic, 19% had a serum [Na+] between 129-135 mmol/liter, and 11% a serum [Na+] of 500 mmol) into an expanded volume of total body water. This Na+ likely originated from osmotically inactive, exchangeable stores. Thus, EAH occurs in athletes who (i) drink to excess during exercise, (ii) retain excess fluid because of inadequate suppression of antidiuretic hormone secretion, and (iii) osmotically inactivate circulating Na+ or fail to mobilize osmotically inactive sodium from internal stores. EAH can be prevented by insuring that athletes do not drink to excess during exercise, which has been known since 1985.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0509096102