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Carb-loading and sports drinks: debunking marathon myths

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Next Sunday, you'll hit the ground running, pushing your body towards the finish line in the Manitoba Marathon.

You're excited and nervous. Nevertheless, you've trained for the event and you know what to do to ensure you complete the event safely.

But are you certain you have all your facts straight?

Ultra-fit University of Manitoba exercise physiologist Dean Kriellaars says too many marathon runners still believe certain myths about running -- myths that can be detrimental to performance and health.

Kriellaars, an assistant professor who trains elite runners, shared with the Free Press some of the most common misconceptions about marathon running. Read on to find out what's real and what isn't:


THE MYTH: I should carbohydrate-load for days before a marathon.

THE REALITY: Planning to down mile-high plates of pasta a few times this week to get your body ready for Sunday's marathon? Kriellaars says carb-loading -- or carb-banking -- for days before a marathon is not necessary or beneficial. But he does suggest consuming a meal high in starchy carbs the night before the marathon. The reason? To increase your glycogen stores. (Glycogen is the fuel muscles need to function properly.) The caveat: Only carb-bank using foods you've eaten before previous marathons or training runs.

"If you haven't practised it in training, you are running the risk of feeling like a slug the next morning," he says, noting that, aside from giving you a bloated belly, high-carb foods you're not used to eating before a run can cause diarrhea come race day. "Certainly that's not a pleasant thing. You'll see people (during the marathon) darting into wherever to do their business."

How much carbs should you take in the night before a race? Kriellaars says six to 10 grams of carbohydrates for every kilogram that you weigh is a good guideline to follow. (Tip: The night before a marathon is the one time you're better off eating white pasta over whole-grain pasta. That's because fibre is difficult to digest and may be hard on your stomach as you're pounding the pavement towards the finish line. Also: fibre slows the digestion of carbs, making them less bioavailable on race day.)


THE MYTH: I need to consume sports drinks during a marathon to replace my electrolytes.

THE REALITY: You've seen the advertisements about sports drinks being a sort of magic potion that contains valuable electrolytes (minerals) that you've lost in your sweat. But unless it's really hot out and you're sweating profusely, most people can stay hydrated drinking a small paper cup of water given to runners at each allocated water station. (At the Manitoba Marathon, water stations are posted at approximately every mile-and-a-half.)

On extremely hot days, of course, it's important to hydrate more consciously.

One way sports drinks do help? By keeping your blood-sugar levels up -- important when your working muscles can deplete the glucose in your body. Kriellaars says you can choose to consume your sugar in the form of drinks, energy gels or gummy bears. The key: Keep your blood sugar up with 40 to 100 grams of carbs every 20 to 40 minutes, depending on your weight and energy output. And don't forget to use the form of sugar you've trained with. (Trying a new gel that you've never had before could lead to dreaded stomach trouble during the race.)


THE MYTH: I don't need to drink fluids during the marathon; doing so will only slow me down.

THE REALITY: "There are runners who will tell me, 'I don't drink anything during a race.' That's just stupid," says Kriellaars, although he notes that someone running a half-marathon on a cool day could get away without taking in fluids during the race. But if it's hot out, or if you're running the full marathon, fluids can be life-saving. The professor says grabbing a cup of water at each hydration station doesn't interfere with race time; Kriellaars teaches the runners he trains how to grab the cup and drink the water all without stopping.

Thinking about ignoring his hydration advice? Kriellaars says heat-related ailments afflict up to 600 Manitoba marathoners every year. "Most of that would have been fixed if they hydrated properly," he says.


THE MYTH: Drink as much water as you can before the race to prevent dehydration.

THE REALITY: Excessive prehydration can lead to hyponatremia, a life-threatening condition in which your body's electrolytes are diluted with the water you've consumed. This sort of water intoxication can lead to an imbalance of sodium and other essential minerals your body needs to function. The end result can be coma or death. So how much water/fluid should you take in before a race? A cup or two is adequate. Instead, hydrate during the race. Kriellaars says you need to replace about half of the fluid that you sweat out.


THE MYTH: If temperatures are too hot and humid during race day, I probably won't be able to complete the race.

THE REALITY: It's true that racing in heat and humidity can be dangerous, since your body won't sweat as much and therefore won't cool properly. Kriellaars says if temperatures soar on race day we'll be in more trouble than ever, considering we haven't been exposed to heat so far this year.

The solution: Get used to the heat by heading to hot yoga. "You need about five to 10 exposures to heat before your body acclimatizes to it," he says. (He often urges runners he trains for the Manitoba Marathon to go to hot yoga sessions in the weeks leading up to the marathon.)

"You can literally go to hot yoga for the two weeks prior. You go every three days. They don't even have to exercise. They can just lie in the hot yoga (room) and the first time they do it, they get dizzy. The second time they do it, not so dizzy. And the third time they do it, they go, 'Oh, my body is adapting,'" Kriellaars told the Free Press in a 2011 interview. As always when in hot conditions, make sure you're constantly sipping water.

(Kriellaars himself prefers to acclimatize himself in his own home. Starting in May, he uses an indoor bike in a warm room with the door closed).


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Republished from the Winnipeg Free Press print edition June 10, 2013 D1

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