Energy Expenditure During Giro d’Italia

A few weeks back, we published an article outlining the physiological demands of riding a grand tour; in conjunction with the start of the Giro d’Italia, this article will explore the energy expenditure and consumption during a grand tour, and also how it relates to performance over such an extreme endurance event.

In the 2014 edition of the Giro d’Italia, one of three grand tours in professional road cycling, seven riders from Belkin Pro Cycling (now Team Jumbo-Visma) took part in a study measuring energy balance.¹ Over 24 days, the riders completed 21 stages adding up to about 3500 km; the riders averaged just over 4 hours on the bike on race days. All subjects completed the race with a cumulative time of around 90 hours.

Over the course of the race, the average daily energy expenditure was 32.3±3.4 mega joules (MJ), which is equivalent to about 7700±800 kilo calories (kcal). To put this in perspective, men are generally recommended to consume 2500 kcal and women 2000 kcal per day.² This is amongst the highest energy expenditures reported in the scientific literature.¹ Despite this, there was no significant reduction in neither body mass nor fat percentage over the course of the race. Thus, despite the remarkable energy expenditure, the riders managed to fuel sufficiently to maintain energy balance.

Within the sample, the average speed varied from 36.9 to 39.0 kilometres per hour (kph) meaning that the slowest rider was 5.6% slower than the fastest. Yet, the fastest rider needed to expend 33% more energy (normalised for body mass) over the course of the race to cover the same distance. So, what underlies this mismatch? Since the study did not measure gross efficiency (i.e., the fraction of energy utilised to sustain mechanical work as opposed to generate heat), one cannot rule out the possibility that the faster rider was more efficient. However, the authors noted that any differences in cycling economy would not wholly explain the variance in energy expenditure. The main discrepancy seems to lie in the different tactics and the environmental effects that follow.¹

The fastest rider was a general classifications (GC) contender and will therefore spend significantly less time sheltered from the wind in the peloton to gain time, especially in the high mountains. Not only does the energetic cost of cycling increase with increased speed, the effect is exacerbated since drag increases exponentially to the increments in speed.¹ At 54 kph, the aerodynamic resistance makes up about 90% of the total resistance. Riding in a closely packed peloton can reduce the aerodynamic resistance to 5-10% of that of an isolated rider. Thereby, for a rider well positioned in a peloton at 54 kph, the drag experienced would correspond riding solo at about 15 kph.³ Thus, the energy cost is largely reduced.

Merely considering the time and distance ridden will not provide an accurate picture of the metabolic demands, since tactics and the environment greatly affect the energy cost of travel. Altogether, these athletes are not only amongst the fittest humans on earth, they also possess the ability to adequately fuel even during the most exceptional conditions.

References

1. Plasqui G, Rietjens G, Lambriks L, Wouters L, Saris WHM. Energy Expenditure during Extreme Endurance Exercise: The Giro d’Italia. Med Sci Sports Exerc. 2019;51(3):568-574. doi:10.1249/MSS.0000000000001814
2. What should my daily intake of calories be?. National Health Service. https://www.nhs.uk/common-health-questions/food-and-diet/what-should-my-daily-intake-of-calories-be/. Published October 24, 2019. Accessed September 12, 2020.
3. Blocken B, van Druenen T, Toparlar Y, Malizia F, Mannion P, Andrianne T, Marchal T, Maas G, Diepens J. Aerodynamic drag in cycling pelotons: New insights by CFD simulation and wind tunnel testing. Journal of Wind Engineering and Industrial Aerodynamics. 2018;179:319-337. doi:10.1016/j.jweia.2018.06.011

Photo by Simon Connellan on Unsplash

Article updated on May 5^th 2023.