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From Brenda in Salt Lake City:

I am trying to work out what is the optimum nutrition for me during an Ironman bike segment. Should it be to take in as many calories as possible?

I figure I am burning probably 600-700 calories an hour over 6 hours. Should I try to get in that much if my stomach can take it?

Thanks,

B.

From Dave Scott:

Brenda, don’t replace a calorie to a calorie! If you try to ingest 600-700 calories per hour, which is probably close to your burn rate, (I would need to know your body weight and average speed to calculate) your GI tract would totally be overloaded. The inevitable outcome is that your energy delivery to your working muscles would stop.

Think of maintaining your energy via a “drip system” regulated by a steady, but not overloaded, stream of food (fluid). This drip system can only take in a smaller portion of calories or it will eventually clog your stomach.

The rule of thumb is to replace 25-33% of your total calories burned per hour. In an Ironman, I would recommend that you replace around 20% in the first hour on the bike and for each hour there after at 25-33%. So, based on your caloric burn of 600-700 calories, the first hour take in approximately 120-140 calories. Each hour there after, assuming you are maintaining the same average output, take in 150 (25% of 600 calories) to 235 (approx. 33% of 700 calories).

Take in an equal percentage of these calories every 12-15 minutes during each hour or 4-5 feedings. A fluid replacement drink that contains carbohydrates and protein, like Accelerade, should be your first source of fuel, then gels and possibly bars.

Good luck!

Dave

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Editors note: Many athletes have found that taking MAP during an Ironman improves performance. We suggest you experiment with this, but 4-5 tablets every 4 hours during the race with your other fuels seems to work very well

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