Int J Sports Med 2011; 32(4): 297-302
DOI: 10.1055/s-0030-1269929
Clinical Sciences

© Georg Thieme Verlag KG Stuttgart · New York

First Reported Cases of Exercise-Associated Hyponatremia in Asia

J. K. W. Lee1 , A. Q. X. Nio1 , W. H. Ang1 , C. Johnson2 , A. R. Aziz3 , C. L. Lim1 , T. Hew-Butler4
  • 1Military Physiology Laboratory, Defence Medical & Environmental Research Institute, DSO National Laboratories, Singapore
  • 2Hope First Response Pte Ltd, Singapore
  • 3Performance Physiology, Singapore Sports Institute, Singapore Sports Council, Singapore
  • 4Exercise Science Program, School of Health Sciences, Oakland University, Rochester, United States
Further Information

Publication History

accepted after revision November 30, 2010

Publication Date:
26 January 2011 (online)


There are no reported cases of exercise-associated hyponatremia (EAH) in tropical Asia. This study aimed to investigate the incidence of EAH at the on-site medical tent and fluid balance in long distance foot races in a warm and humid environment. Body mass was taken before and after the races (42-km marathon; 84-km ultra-marathon). Blood sodium concentration was measured for symptomatic runners admitted to the medical tent. Mean (SD) dry bulb temperature was 29.0 (0.6)°C, relative humidity 89 (2)% and wind speed 0.3 (0.5) m/s. Three out of the 8 symptomatic runners admitted to the medical tent were diagnosed with hyponatremia, with blood sodium concentrations of 134 mmol/L in a 42-km runner, and 131 and 117 mmol/L in two 84-km runners. In the 42-km race, mean % ΔBM was −1.6 (1.2)%, ranging from −5.7 to 1.4%, and 22 runners (7%) gained weight. In the 84-km race, mean % ΔBM was −2.3 (1.7)%, ranging from −8.0 to 1.4%, and 9 runners (8%) gained weight. In addition to the 3 cases of symptomatic hyponatremia observed, 8% of the 84-km runners and 7% of the 42-km runners gained weight during the race. This indicates the need to disseminate advice for the prevention and treatment of EAH for races held in the tropics.


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Dr. Jason K. W. LeePhD 

Defence Medical & Environmental

Research Institute

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