The Giro: its energy cost

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Watching a stage of the Giro d’Italia in the Dolomites is quite literally dumbfounding. The riders climb for lengthy stretches up mountains, at an average speed of 40 km/hour.
This also raises a couple of questions. «What is the energy cost of this? And what is the energy cost for the entire Giro, as the riders spend three weeks fighting it out at their physical limits?»


Of course, you’ve probably already heard tales of how much the riders eat during these weeks. We also know they take nutritional energy supplements to increase daily calorie intake, especially during stages. I guess it’s fair to think that high intensity training every day for hours on end helps top professionals develop some sort of energy saving ability that more mortal cyclists can only dream of. But is this really the case?

Mechanical movements have a cost. And there are no discounts

Let me be clear straight away: there is no definitive evidence that by training every day a professional athlete can achieve energy savings during a race. There is also no certainty about a discount, but it would seem they pay the full price.


We know that such athletes are very light, their bikes weigh next to nothing, their cycling position is always aerodynamic and the slipstream created by the other riders is a huge benefit. Still, even taking all of this into account, it hardly seems possible that training can significantly reduce the number of calories that need to be consumed to reach the finishing line.


A professional cyclist has a body that is finely trained to produce energy, making it possible for such athletes to cycle so fast for such sustained periods that normal cyclists can’t even imagine it, but this doesn’t mean they burn less calories – or, at least, it’s not clear they burn less.

In other words, a professional cyclist can produce far more energy, but isn’t able to save energy given the same level of mechanical movement.



Energy cost of the stages

How many calories are needed for a stage in the Giro? An extremely recent publication of the results from a study involving 9 professionals from a UCI World Tour team during a similar race – La Vuelta or Tour of Spain – has provided some current information.


As expected, the energy cost figures for the individual stages are very high, although they do vary according to the cyclist’s weight, average speed during the stage, length and the amount of climbing.

In the Spanish study, during one flat stage it was found the calories consumed ranged from 2,500 to 4,000. During a hilly stage, the figure rose to between 3,000 and 4,500 and for a high mountain stage, to 4,000 to 5,500.

Even higher figures are also not unheard of. Since 100 g of pasta has less than 350 calories, it is pretty easy to see how hard it must be to maintain an acceptable energy balance (intake and expenditure) while racing in a three-week event.


There are other factors – notably two – that make this even more complicated. First, during a stage race, a cyclist only actually eats two proper meals per day: breakfast and dinner. And the timings for these are often not ideal, because of the organisational problems caused by moving in the afternoon or evening between the end of one stage and the start of the next.


Second, strenuous physical exercise greatly reduces appetite, hence the tendency to reduce food intake from the first to the second, and especially the third week of the race, when fatigue really starts to set in.



How professionals manage carb intake

Fortunately, many steps forward have been taken, especially in the first decade of this century, in understanding the physiology of digestion and intestinal absorption of carbohydrates.


This has provided a basis for knowing the optimal ways for a cyclist to take supplements during a race, such that enough is consumed to maximise digestive and absorption potential, but not too much to cause gastrointestinal stress.

Using the right mixes of glucoseor, better still, its polymers (maltodextrins), and fructose, one can take in about 90 g of carbs for every hour of cycling. In a 5-hour stage, with a slight break in consumption, this adds up to about 400/450 g of carbohydrates.

Following (not always completely) these indications, the professional cyclists involved in the study during La Vuelta ingested between 65/70 and 100/115 g of carbohydrates per hour of racing.


The paper’s authors did note that, in some cases, these amounts might have been overestimated given the complexity of determining precisely how much a cyclist actually drank during a race stage.


Still, no matter how well this is done, it is almost never enough to compensate for the energy cost of the race, since in a 5-hour stage, it “only” equates between 1,300 and 2,300 calories.


Thus the need to consume additional carbohydrates in the hours following a race, during meals – breakfast and dinner – and at other times, whenever possible. Adopting such an approach, the cyclists studied during the Spanish study managed to consume between 750 and 1,050 g of carbohydrates in a 24-hour period. This equates to over 12 g per kg of a cyclist’s weight.



Total calorie intake during a 3-week stage race

Taking account of other nutrients, namely fats, consumed less than the recommended daily amount, and protein, consumed more than the recommended daily amount, the average calorie intake during a complete day of La Vuelta was between 4,500 and 6,500.


Such overall calorie intake along with the significant protein intake still results in a slight weight loss (about 1 kg) for the cyclists over the course of the three-week race. Such loss can be put down solely to fat mass though, leaving the muscle mass the same.


  • Muros JJ, Sanchez-Muñoz C, Hoyos J, Zabala M. Nutritional Intake and body composition changes in a UCI World Tour cycling team during the Tour of Spain. Eur J Sport Sci. 2019;19:86-94
  • Westerterp KR, Saris WHM, Van Es M, ten Hoor F. Use of doubly labelled water technique in humans during heavy sustained exercise. J Appl Physiol. 1986;61:2162-7
  • Saris WH, van Erp-Baart MA, Brouns F, Westerterp KR, ten Hoor F. Study on food intake and energy expenditure during extreme sustained exercise: the Tour de France. Int J Sports Med. 1989;10 Suppl1: S26-31
  • Rehrer NJ, Hellemans IJ, Rolleston AK, Rush E, Miller BF. Energy intake and expenditure during a 6-day cycling stage race. Scand J Med Sci Sports. 2010;20:609-18



A physician and specialist in Food Science and Gastroenterology, he is also an Adjunct Professor at the Postgraduate School of Specialisation in Nutrition Science in the Medical Faculty at Milan State University. He is the Head of the Sport Nutrition Unit at Mapei Sport Service, a sports medicine clinic and research centre in Olgiate Olona, northwest of Milan. He is a nutrition consultant for many professional athletes and teams in a range of sports, including Giro d’Italia and Tour de France winners, teams in the Italian Serie A football league, national athletics champions and a female downhill skiing Olympic gold medallist. He joined Equipe Enervit in 2008.