Hyponatraemic encephalopathy despite a modest rate of fluid intake during a 109 km cycle race. British Journal of Sports Medicine, 39(10): e38.
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2005
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British Journal of Sports Medicine
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University of Cape Town
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Objective: To report a case of exertional hyponatraemic encephalopathy that occurred despite a modest rate of fluid intake during a 109 km cycling race. Methods: Men and women cyclists were weighed before and after the race. All subjects were interviewed and their water bottles measured to quantify fluid ingestion. A blood sample was drawn after the race for the measurement of serum Na+ concentration. Results: From the full set of data (n = 196), one athlete was found to have hyponatraemic encephalopathy (serum [Na+] 129 mmol/l). She was studied subsequently in the laboratory for measurement of sweat [Na+] and sweat rate. Conclusions: Despite a modest rate of fluid intake (735 ml/h) and minimal predicted sweat Na+ losses, this female athlete developed hyponatraemic encephalopathy. The rate of fluid intake is well below the rate currently prescribed as optimum. Drinking to thirst and not to a set hourly rate would appear to be the more appropriate behaviour.
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Dugas, J. P., & Noakes, T. D. (2005). Hyponatraemic encephalopathy despite a modest rate of fluid intake during a 109 km cycle race. British journal of sports medicine, 39(10), e38-e38.