Race/Training Nutrition Intake.....

As runners, many of us enjoyed a long, cool spring, full of perfect running days, but the recent heat wave that has crossed the country was reminiscent of the most recent surprising heat wave: The 2007 Chicago Marathon weekend. Organizers were criticized for running out of water, cups and ambulances. In light of this, you might be surprised to learn that only 40 years ago, race organizers were not allowed to provide fluids before the 11 kilometer mark of a marathon and after that point runners could only drink once every 5k, according to the IAAF rule number 165.5.

In fact, this rule was more relaxed than the 1953 version which specified that "refreshments shall [only] be provided by the organizers after 15 km.No refreshments may be carried or taken by a competitor other than that provided by the organizers." We've certainly come a long way from those days, but, as Tim Noakes points out in his tome The Lore of Running, we now have a tendency to overdo it a bit. We're not talking about hyponaetremia (or overhydration) but we're simply drinking more fluids than it is possible for our bodies to absorb when we are in a stressed state.

During competitive running, its just not possible to replace fluid at rates equal to sweat rate, due in part to gastrointestinal distress. Noakes found in a 1993 study, that both fluid and carbohydrate absorption from the intestine was lower than expected during exercise. He found that while running, athletes had a hard time absorbing more than approximately 700 milliliters (about 23 ounces) per hour. If they tried to drink more than this, they felt bloated, which indicated some volume of unabsorbed fluid in the intestine.

"The only runners who are capable of drinking [enough to keep up with their sweat rate] are those who develop water intoxication (hyponaetremia)," and they tend to be the back of the pack runners, who are running slowly enough to be able to take in so much fluid. In contrast to popular belief, Noakes says that NOT all of the weight loss over a long run or race needs to be replaced in order to maintain performance. Indeed, when runners were tested after hot races, it was found that those with the greatest degree of dehydration were the winners.

So how does all this apply to you? While you're running and racing this summer, drink. When you're thirsty and not too much. About 16 ounces (1 pint) per hour will be as much liquid as most of us can absorb.

(Running Times Training Newsletter, June 2008)