Too much fluid hazardous

Too much fluid during endurance exercise can be hazardous, even resulting in life-threatening seizures and coma, a symposium in Queenstown has been told.

Associate Professor Ian Rogers, of the Sir Charles Gairdner Hospital in Perth, is encouraging athletes to limit fluid intake during endurance events - which he defined as moderate-to-high exertion over four or more hours.

Professor Rogers, the hospital's director of postgraduate medical education and research, said intake should be no more than 500 to 750ml an hour.

But he acknowledged that changing drinking behaviour could be challenging in a setting where the mantra "if you don't drink you die" had become part of sporting folklore.

"The commonest medical problem is exercise-associated collapse, which usually occurs at the end of a race when exertion ceases and the enhanced blood flow to maintain cardiac output is lost."

It was due to simple intravascular volume depletion and usually required no more than rest in a supine posture and oral fluids.

The most frequently encountered severe medical problem was dilutional hyponatraemia - a low level of sodium in the blood due to overhydration, Professor Rogers said.

It was most common in female and slower competitors and had been conclusively shown to be due to excess fluid intake during an event.

- NZPA