Drafting

Anyone who has participated in a mass-start ski race knows that drafting helps. Leading the pack is usually not advisable as it drains energy and strength. But how beneficial is drafting in races?

The advantage of drafting in cross-country skiing is significant, although not as great as in cycling. This tactic, skillfully used by skiing legend Petter Northug in mass-start competitions, is scientifically proven to save energy and optimize performance. While drafting is a well-established strategy in cycling, its importance in cross-country skiing has been less understood—at least until now. A study from Mid Sweden University’s Sports Tech Research Center sheds light on how much energy top skiers can save by staying behind a competitor in the slipstream.

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Scientific Findings on Skiers’ Drafting

The Swedish study, led by Mats Ainegren, used a wind tunnel and treadmill to analyze how drafting affects oxygen consumption (VO2) and heart rate among elite skiers. Twenty athletes (10 men and 10 women) participated in the study, using the traditional double-poling technique at varying speeds.

Key findings:

• For men, drafting reduced oxygen consumption by 3-5% when skiing at speeds of 5 m/s (18 km/h) or higher.
• For women, oxygen consumption decreased by about 2.5%, but only at speeds of 6 m/s (21.6 km/h) or higher.
• Heart rate decreased correspondingly with reduced oxygen consumption, indicating an overall reduction in energy expenditure.

Though seemingly small, these savings are significant at the elite competition level. A 3-5% difference in oxygen consumption is comparable to the energy saved by a skier with good technique compared to a mediocre technique.

Drafting in Skiing vs. Cycling

While drafting is an effective strategy in cross-country skiing, it is not as impactful as in cycling due to the different mechanics and conditions of the sports:

• Air resistance: In cycling, air resistance can account for up to 90% of energy expenditure at high speeds, making drafting critical. A cyclist can save up to 30-40% of their energy by staying behind another rider.
• Terrain variation: Skiing routes often include climbs, descents, and turns, which break the continuous drafting opportunities, unlike cycling’s relatively flat roads.
• Yo-yo effect: In a long line of skiers, speed variations, especially on climbs, can negate energy savings as skiers must brake and accelerate again.

Despite these differences, drafting is a valuable tool, especially on flat sections and in headwinds, where the effect of slipstreaming is greatest. In races like Vasaloppet and World Cup mass starts, energy savings can be crucial for decisive moments, such as the final sprint. It is also worth noting that in skiing, the trailing skier often benefits from better glide compared to the leader, especially on downhills, due to ski equipment and snow conditions.

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Implications for Elite and Recreational Skiers

The study highlights that drafting is most beneficial at high speeds, typical for elite skiers. Recreational skiers who ski at slower speeds gain less benefit from drafting unless there is a strong headwind.

For top athletes and coaches, the research underscores the importance of incorporating drafting tactics into training and race planning. Identifying the right moments and places for drafting can save energy for critical moves.

Drafting in Mass-Start Races

Mass-start competitions, such as the Ski Classics Pro Tour, World Championships, and the Olympics, offer prime conditions for the central role of drafting. Flat sections and long distances emphasize energy savings in the slipstream.

However, the dynamics of skiing in large groups complicate the strategy. Leading increases visibility and reduces the risk of accidents but is more costly in terms of energy expenditure. Conversely, skiers in the middle of the group can save energy but must handle the “yo-yo effect” of speed fluctuations.

Also Read: Drafting in skiing demystified

Conclusions

The science of drafting is reshaping our understanding of cross-country skiing tactics. While the effects are not as pronounced as in cycling, a 3-5% energy saving from drafting can make or break a top performance. As skiers refine their strategies, drafting remains a critical tool for maximizing performance and timing decisive attacks.

Coaches, analysts, and skiers can now better quantify the benefits of drafting, enabling smarter decisions in training and competition. Next time you watch a mass-start race, pay attention to the skiers saving energy by staying behind the group—they might just be the ones sprinting to victory at the finish line. And when you head to your next mass-start ski race, find a suitable group with a pace slightly faster than you could manage alone, to best benefit from drafting during the race.

You can read more about the Swedish study here. This article is based on an article published a few years ago by Johan Trygg on the Langd.se website.