RT Journal Article
SR Electronic
T1 Hyponatraemic encephalopathy despite a modest rate of fluid intake during a 109 km cycle race
JF British Journal of Sports Medicine
JO Br J Sports Med
FD BMJ Publishing Group Ltd and British Association of Sport and Exercise Medicine
SP e38
OP e38
DO 10.1136/bjsm.2005.018820
VO 39
IS 10
A1 J P Dugas
A1 T D Noakes
YR 2005
UL http://bjsm.bmj.com/content/39/10/e38.abstract
AB 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.