le Tour de France 2008: Feed them well  //  Why eating is important

08 Jul 2008 Posted by
The 2008 edition of le grande boucle, as it is affectionately known, is now fully underway, and so far each stage has been quite exciting. The tour started without the traditional prologue, and instead was a full on stage. It’s slightly uphill finish effectively neutralized the sprinters, and so it was not surprising to see all the main GC contenders at the front. In fact Alejandro Valverde won the stage and took yellow, although we spoke about how much of a challenge it would be to go “wire to wire” in yellow.

Sunday’s Stage 2 had its fair share of bumps with four categorized climbs and also a slightly uphill finish. It seemed that again the sprinters would be neutralized, and it was Fabian Cancellara that attacked with one km to go. He could not hold it, though, and even Valverde had a go, but also faded. In the end a big man took victory—Thor Hushovd from Norway powered across the line for his fifth stage win in le Tour. Valverde remained in yellow, however.

During the first two stages there were crashes as the riders passed through the feedzones. These are designated areas where support crew hold out bags full of food and drink. The riders slow down a bit and grab them as they whiz by. Fortunately Stage 3 saw no crashes in the feed zones, but let’s looks at why it is so important to eat on the bike.

Energy balance

We can all agree that the energy demands placed on tour riders are pretty astronomical, but it makes more sense to break it down into a specific context. Therefore let’s take your “average” 75 kg cyclist and his daily energy demands. His resting metabolic rate, or RMR, is the amount of energy he requires to sit there do nothing all day long. In other words, it is the energy required by his body to maintain all of its life-sustaining functions. For him it is around 1500 calories.

But our cyclist is not just sitting there all day. . .in fact, he is covering upwards of 180 km per stage, often with significant uphill sections which require more energy. Cycling is a pretty efficient activity, however, and it costs our cyclist in the range of 0.3-0.4 calories per km cycled per kg of body mass—or about 25-30 calories per km. The bottom line here is that a 180 km stage will cost our athlete around 4000 calories, depending on the amount of drafting.

It’s a lot of cheeseburgers!

Any way you calculate it, our cyclist’s total energy expenditure for one day of the tour is very high. His RMR (1500 cal) plus his exercising energy expenditure (4000 cal) adds up to a whopping 5500 calories, which is probably the equivalent of 15+ cheeseburgers! So just to remain in energy balance our rider must consume 5000+ calories a day. Believe us when we say it: that is a lot of food. Add to this the fact that he is on the bike for four or more hours during the day, plus the “anorexic effect” of exercise, plus 8-10 hours of sleep. Suddenly he has only a relatively small window of time to consume large amounts or calories.

If we assume he is otherwise occupied for up to 16 hours a day with riding, sleeping, and other activities, he has only about 7-8 h to ingest 5500 calories, which works out to about 700+ calories an hour during the time he is available to eat and drink. So remaining in energy balance is actually a huge challenge for our tour rider.

Fortunately the race organizers allow the cyclists to grab the feed bags and eat while riding. This is crucial for two reasons. First, it provides more opportunity to choke down a portion of the 5500 calories he needs in a day. Second, the ingestion of carbohydrates during exercise prevents the dreaded “bonk,” or hypoglycemia. Many of you probably have bonked before, and therefore you know that when it happens you are finished—no more racing for the day as you limp home and consume gross quantities of food along the way to fill the hole in your tummy!

How much to eat then?

Klaas Westerterp and his colleagues in Maastricht (Netherlands) actually measured the energy intake and estimated the energy expenditure in five cyclists in the 1988 Tour de France. Their average intake was almost 6000 calories per day, while their average expenditure was nearly 6100 calories per day—indicating that these cyclists did a remarkable job of (nearly) maintaining energy balance. They accomplished this by ingesting 49% of their energy while riding, which amounted to whopping 94 g of CHO per hour during each stage! Furthermore, a full 30% of their carbohydrate intake was in fluid form, which makes it substantially easier to meet energy requirements during the 7-8 h when they are not racing or otherwise occupied.

Given this information now, it should now make total sense when you watch the riders rolling through the French countryside, shoving energy bars and other products down their gullets. Hungry or not, they must get the calories into their bodies. Failure to do so will almost certainly result in fatigue and an early exit from the race, because when cycling four or more hours each day it does not take long to accrue a serious energy deficit. When your body does not get enough energy, cycling four hours or more a day becomes an unnecessary activity, and our bodies have an uncanny way of keeping us healthy—suddenly getting on the bike and pedalling requires substantial effort, more so than a few days ago, and eventually you will not be able to keep up with the bunch.

Stay tuned to le Tour—plenty of action ahead

Looking ahead to Tuesday’s stage, we see the first individual time trial. It is a pancake flat 29 km ride and will do two things. First, it will create a pecking order for those who will contend for the GC. Second, it will limit any one rider’s gains or losses as the distance is so short, and therefore the race should remain close and within reach for the contenders. It also will set the stage for Stage 6 on Thursday, which is the tour’s first mountain top finish, and is sure to produce some fireworks!

This post is part of the following threads: Tour de France Analysis, Tour de France timeline – ongoing stories on this site. View the thread timelines for more context on this post.