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Ironman Triathlon Training: Hyponatremia and Hydration
 
P. Mauro – 2005
 
It wasn’t too long ago when athletes in the Ironman triathlon were told to take on board as much water as they could to prevent dehydration. They were told to get most of this during the bike as access to fluids in the swim isn’t possible, and it’s harder to swallow fluids whilst running. ‘Drink before you are thirsty’ was the usual mantra.
 
Well that advice just doesn’t cut it these days, and athletes need to take a much more calculated approach with their rehydration strategies. Over-hydration (drinking too much water) can result in a serious condition known as Hyponatremia. This condition can result in serious consequences such as death.
 
Are you thinking that this doesn’t apply to you? THINK AGAIN. A study by Speedy et al (1999) reported that 18% of the 330 race finishers at the 1997 New Zealand Ironman triathlon were hyponatremic. The authors concluded that fluid overload was responsible for 73% of those individuals with severe hyponatremia. It was also found that 29% of the athletes in the 1984 Hawaiian Ironman triathlon had developed the condition. In addition, Davis et al (2001) chronicled 26 cases of symptomatic hyponatremia from the 1998 and 1999 San Diego marathon events. The average finish time for the 26 runners was 5 hours, 38 minutes (range = 4:00 to 6:34), and many runners admitted drinking as much fluid as possible during and after the event. How much did they drink? That remains unclear, but plasma sodium values ranged from 117 to 134 mmol/litre, so excessive drinking is a strong possibility. Moreover, sweat sodium loss—although not measured in this study—likely contributed to the problem.

Hyponatremia: The Facts

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