Science Interviews

Interview

Sun, 8th Aug 2010

Eating your way to Endurance

Fergal Grace, Kingston University

Listen Now    Download as mp3 from the show The Tour de France

Meera -   So far, we’ve heard how scientists can train their body to handle the endurance required to finish the tour, but what about their diet?  As well as being fit, they need energy to keep them going.  I went back to Kingston University to ask Dr. Fergal Grace about the calories and nutrients consumed, and needed by these elite athletes.

Fergal -   After three weeks of cycling, a cyclist who’s actually finished the tour is going to have expended approximately 120,000 calories while they were on the bike. We can equate that to about 14/15 pounds of fat.  You can take it that they need to consume vast amounts of calories just to finish the tour.  The calories that they'll take on board fruitsare going to be a normal athlete’s diet - which is a minimum of 60% carbohydrate, 10% protein, and the remainder is fat.  And what they will do is up their carbohydrates, maybe lower the fat intake, and as they're cycling, they're going to take simple carbohydrates as gels and high energy drinks, as opposed to hard meals.

Meera -   What sorts of simple carbohydrates?

Fergal -   Glucose, fructose, galactose. Taking onboard simple carbohydrates like that  takes away the process by which the body has to break down the carbohydrates, so they become immediately useable as a fuel.  Now if somebody is exercising for periods of greater than one hour, blood glucose levels – when you exercise at a moderate level of intensity after one hour, start to decline.  They're going to have to keep this topped up while they're on the bike.  Another thing that they will avoid doing is taking onboard simple carbohydrates immediately before exercise because if you take these simple carbohydrates immediately before exercise and start to exercise, you get an insulin spike and a drop in blood glucose.  So they get what’s called "rebound hypoglycaemia" which is a rapid drop in blood glucose level, right at the moment that they need to have stable amounts of glucose.

 

Glass of WaterMeera -   And what about hydration? Especially, I think in this year’s tour, temperatures reached ridiculous levels.  It was in the high 30s at points, so how important is hydration and how should that be monitored or kept?

Fergal -   Yes.  Well, hydration is absolutely imperative for anybody involved in any type of exercise activity.  A drop in approximately 2% of your body weight (so if we’re talking for a 50-kilo male - a drop of about 2 kilograms or 2 litres of fluid) can result in a drop in performance of between 10 and 20%.  The cyclists in the tour will be hydrated before the race and they will consume approximately 1 litre of water per hour, at a constant rate.

Meera -   What about energy drinks?

Fergal -   Energy drinks or replacement drinks are generally high in carbohydrate.  So they'll have some complex carbohydrate, but mostly simple sugars.  You know, many of them will have some amino acids in them, so you may branched-chain  amino acids added in, and they are good.  They're a good source of getting the high energy into the body quickly.

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