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It’s stage 12 of the 2018 Tour de France and the leaders have reached the final climb of the day: the legendary Alpe d’Huez. Colombian sensation Egan Bernal (Sky) is leading a group of GC favourites up the mythical ascent, steadily ticking off the 21 switchbacks as he goes.
As the contenders pierce through the orange flare smoke that blankets Dutch Corner, Bernal is still there at the front, tapping out his infernal tempo. Sitting directly behind him are two of his teammates: overall leader Geraint Thomas and defending champion Chris Froome. Bernal’s stellar ride will help reel in lone leader Steven Kruijswijk and set Thomas up for a second consecutive stage victory.
While we’re used to seeing teams lined up in the mountains, their leaders safely ensconced near the back, the reasons for this strategy aren’t immediately obvious. Drafting makes sense on flat roads — the less time a leader spends in the wind, the less energy they’ll expend, and the more they’ll have in reserve when it counts. But when riding uphill, the impact of wind resistance is significantly reduced; instead, it’s gravity that becomes the riders’ biggest anchor.
Why then do the strongest teams line themselves up in the mountains, sheltering their leaders as they would on the flat? Does drafting uphill actually provide some benefit, or is it simply the done thing?
Theo Ouvrard is a coach with the French Pro Continental team Fortuneo-Samsic and a researcher at the Sports University in Besancon, France. As part of his PhD he recently led a study that looked at the benefits of uphill drafting “What interested us, with my director, is the impact of having this teammate in front of the leader, not only of classical biomechanical aspect but also on psychological aspect,” Ouvrard told CyclingTips.
For the study, Ouvrard and his colleagues recruited 12 strong amateur cyclists1 to ride up a 2.7km (7.4% average gradient) climb a total of three times. The first ascent allowed the riders to familiarise themselves with the climb. The next two times were used to test whether having a teammate to follow resulted in a faster ascent time.
“[They did] one completely alone as a classic time trial or as if you are in a breakaway alone, and another one with a teammate in front of the participant,” Ouvrard said. “The teammate for this condition was stimulated by an experimenter — it was me, in fact — on [an] e-bike.”
For the sake of verisimilitude, the use of an e-bike (compared with a scooter, say) was important. Ouvrard and his colleagues wanted the trial to feel as lifelike as possible for the study participants — the leading teammate (Ouvrard on his e-bike) had to be putting in a cycling effort. Ouvrard would start the climb at the pace the rider had recorded during their familiarisation ascent, and would then respond to commands from his “team leader” behind.
“We put the e-bike only on the low-power mode and the leader have to adjust by speaking to me, to say ‘go’, to say ‘wait’,” Ouvrard explained. “And so it [had] to really respect the real condition in the field when the teammates have to [set] the tempo … but also that the leader can adjust to go faster or to go slower.”
The riders’ heart rate and power output were monitored throughout both ascents. At the top of the climb, the researchers set up a small field laboratory, allowing for further comparison between the two efforts. They tested for physiological differences, such as blood-lactate concentration, and also psychological differences, such as the riders’ rating of perceived exertion (RPE), how much pleasure they took from the effort, and the sort of motivation they felt while climbing.
Of course, they also recorded the time it took each of the study’s 12 riders to complete the climb solo, and with a teammate leading them.
Ouvrard and his colleagues came away from the study with two main findings. The first was that, on average, a rider’s climb time was improved by 23 seconds when they had a teammate to follow. “We find that the teammate helped the leader to improve his performance by 4% approximately,” Ouvrard said.
That’s an interesting finding, for a number of reasons. No significant differences in power output were observed between the two conditions, likewise no differences in heart rate, post-effort blood lactate concentration or RPE. In short, the riders had gone faster for the same physiological effort, leading the researchers to deduce that a good percentage of the performance gain (13 of the 23 seconds) had actually been due to a drafting effect.
“A little bit more that half of this gain [is] due to the drafting effect, even if it’s in a steep uphill,” Ouvrard said. “So for the same power we go faster.”
The question of gradient
The climb used in Ouvrard’s study has an average gradient of 7.4% — a reasonably steep ascent. And the magnitude of this gradient is significant: the 4% performance gain found by the researchers is tied directly to the gradient of the climb.
On a shallower climb the speed of the riders would be faster (for a given power output), thereby increasing the wind resistance they’d encounter (wind resistance is proportional to the rider’s speed, cubed). In that setting, the benefit of drafting a teammate would increase. On a steeper climb, by contrast, drafting becomes less effective — the speed is lower and so too the impact of wind resistance.
Ouvrard was surprised to learn there was any benefit to drafting at 7.4%.
“Classically, at a higher grade [following a teammate is] supposed to already have no effect [of drag reduction],” he said. “I saw a paper that said that for a grade higher than 7% it already [has] no effect on the drafting effect. And so it was really a surprise to see that it still [has] a strong effect on this steep grade.
“The aerodynamic gain only is almost 15 seconds, so it’s really really important for a climb which is lasting eight minutes approximately. Yes, of course [the performance gain] depends on the grade of the climb, but we have to keep in mind that [drafting is] still important on a steep climb like that.”2
Ouvrard’s second main finding was that when riders had a teammate to follow, they were able to deliver a stronger end spurt — a better time for the final 10% of the climb.
“It’s more than 20 watts [extra] in the last sprinting effort,” Ouvrard said. “For us it’s also a sign that it’s psychologically different [having a teammate to follow] in terms of regulation of effort and feeling things.
“Maybe this strategy can help the leader thanks to the drafting effect but also to be psychologically a little bit preserved, in order to do a stronger push at the end of the effort.”
Psychologically, there was another benefit too. Participants found it significantly more pleasurable (+41% on average) to have a teammate to follow, compared with riding the climb alone. That’s a finding that will be of little surprise to anyone that’s ridden an individual time trial before.
Teammate vs opponent
So if a rider can benefit from drafting even on a reasonably steep climb, does that draft need to come from a teammate? Couldn’t they just get the same benefit from following their rivals?
When it comes to drafting, yes — the aerodynamic advantage is likely to be the same. It might even deliver the same psychological benefit.
“I think … there are no big differences on the psychological theory about looking at a teammate or looking at an opponent,” Ouvrard said. “The first study to analyse that psychological effect [did] it mainly with opponent[s] and there [was] a strong effect on the performance.”
“I think on the climb … the main benefit is that the teammate will do exactly the pace that the leader needs.”
Think of someone like Tom Dumoulin — a rider with a big engine that is more suited to time-trialling up a mountain at a constant tempo than surging and slowing like the smaller, punchier climbers. For Dumoulin, following teammates at a steady tempo is going to be preferable to following rivals who might vary their tempo more.
And there are other benefits of uphill drafting that aren’t related to aerodynamics. Sittting behind a teammate gives the leader a reliable wheel to follow in the unpredictable chaos of a bike race — a friendly place to focus their attention.
And then there’s the fact that a consistent tempo at high intensity can help dissuade others from attacking, a fact Team Sky knows all too well. After all, when you’ve got your rivals at their limit just following you, it’s going to be near impossible for them to find a little bit extra to get off the front.
Amateur vs pro
The riders in Ouvrard’s study were all strong amateurs which makes it a little complicated to extrapolate his finds to the very best in the world. But Ouvrard believes that, given the same test protocol, the best professionals would demonstrate a greater performance increase while following a teammate than the amateurs did.
“Maybe one of the limits of our study [is] that our riders are competitors but they are not professional riders or, even more, a true leader that competes for the general classification,” he said. “If you do the same study with a really true leader, a true GC leader, maybe they will be more focused on the teammate … and maybe the effect will be, for me I think, maybe a little bit higher, psychologically.”
So what can we learn from this research? The biggest take-away is that there is perhaps a greater benefit in drafting uphill than might have been expected, given previous research in this space. Then again, this is just one study — more work will need to be done to replicate Ouvrard’s findings.
In some ways it’s obvious that there’s a benefit to following teammates uphill. Beyond the ability to control the pace, dissuade attacks and so on, it’s significant that this strategy is already used extensively in the pro peloton.
“I think when I saw this result I got firstly surprised,” Ouvrard said of the 4% performance gain.” But then after thinking about it: why [do] a team like Sky always do that? I think that … they already know this result, that it’s important to have the guy just in the front of the climb.
“They already know that having the teammate just on the front can help out a lot with the drafting.”
But it isn’t just the best of the best that can take advantage of small performance gains in the mountains.
“Marginal gains — it can be effective for everyone,” Ouvrard said. “Participants of our study … some are national level — but also some [are] regional level. Some of them really have a good performance improvement with [following a teammate uphill] so it shows that even at this [level] … you will be faster even on the climb if you take the wheels.
“The main result, I think, can be translated to everyone.”
For those that love the challenge of taking on Strava KOMs, this research should be of particular interest.
“I don’t know if it is already popular in Australia but here in France … Strava is really popular — all the rider want to be the leader of the KOM,” Ouvrard said. “I remember when I was young we do the [lead-out] train to help a friend take the KOM. That’s also a way to benefit from the drafting effect even during a climb.
“And the other result maybe is to more recreational riders who want to perform better … psychological aspects are really neglected. People don’t really think about [the need to] be confident, or be focused on the good thing and not be focused on the pain and the legs. There are lot of studies which are showing things like that and I think that this study, it’s not very strong evidence about it, but [it’s] one of the studies that shows that for everyone the psychological aspects are important.”
Unlike the world’s best, we amateur riders might not have the luxury of a strong team of climbers to support us in races or when tackling a local KOM. But as Ouvrard’s research seems to show, we can all benefit from having even just a single teammate to pace us up a climb. And as for the likes of Geraint Thomas, Chris Froome and other Grand Tour contenders, it would seem that their strategy of drafting teammates uphill isn’t going anywhere anytime soon.
1. The riders had an average maximal aerobic power of 5.8 W/kg.
2. Beyond a certain gradient, the aerodynamic benefit of drafting shrinks into insignificance. Given that, does it only make sense to follow teammate on climbs up to a certain gradient? Not quite, because as mentioned later in the piece, there are several reasons to follow a teammate, not just those related to aerodynamics: having a steady tempo to follow, dissuading others from attacking, and having something to focus on, to name just a few.