47. WATT SAVED WHEN DRAFTING ON THE CLIMBS

Image from Van Druenen et al. 2021 (1).

It is well known as on flat terrain drafting permits to save a lot of power as air resistance is the main force to overcome. However, when riding on the climbs, the force of gravity becomes the main resistance to overcome. This could question drafting benefits. However, in professional road races, we often saw leaders drafting behind their teammates and following attack even if the optimal pacing strategy would suggest to not do it.

Is drafting beneficial when riding on the climbs? If yes, how much?

A study published by Van Druenen and Blocken (Eindhoven University of Technology) on Sports Engineering in 2021 tried to answer this question. (1)

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WHAT DID THEY DO?

• Wind tunnel simulations were performed in the following conditions:

  • pacelines up to 8 cyclists manikins

  • slope gradient: 7.5%

  • speed: 21.6 km/h, which approximately corresponds on what pro cyclists usually record on long efforts (~20min-1h) on this slope gradient. The watt saved when drafting on the same slope at other speeds were derived with calculations.

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WHAT DID THEY FIND?