Question: 

I’ve decided to compete in the IRONMAN 70.3 Dubai in 2016. What’s the science behind preparing my body so I can keep going?

A big endurance commitment like this requires big pre-fueling. A half-Ironman (70.3 miles) pace – if you are pushing yourself hard – means you are performing at around 70-80 percent of your maximum pace, or intensity, for at least five hours.

If the course has some climbing sections (Dubai won’t), or when you sprint to overtake someone, or speed up to the finish line, you’ll be running at between 85-95 percent of your maximum pace. The higher the percent of maximum intensity, the higher the percent of carbohydrates that you will burn for fuel. Even if you have been eating a zero carbohydrate diet, you always need them as a fuel.

Research has shown that around 10g of carbohydrates/kg of body weight, for a few days up to a race, are needed to fully pre-fuel muscle with stored carbohydrate (glycogen). But there is an added bonus: carbohydrates stored in muscle are packed with up to four times more water. Like a camel holds extra water in its bloodstream, water stored with muscle glycogen can act like a hydration reserve tank—an oasis in the desert during a desert 70.3. Choose carbohydrate-rich foods and supplements that you tolerate well, with minimal to zero bloating, and expect to gain up to 2.5kg weight (maybe more). But don’t worry, you will lose all of it by the time you finish!

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