Heading out the door? Read this article on the new Outside+ app available now on iOS devices for members! Download the app.
It was a sight to behold. Caleb Ewan, his body perched precariously over the front of his bike, his head somehow below the line of his handlebars as he barrelled towards the finish line at more than 60kph.
The Aussie speedster’s new sprint position looked as dangerous as it did unusual — one bump from a fellow rider or imperfection in the road and Ewan was almost certainly hitting the tarmac, face first. But as dangerous as the position looked, there could be no doubting its effectiveness. That week, at the 2016 Tour Down Under, Ewan won three sprint finishes.
In the years since Ewan debuted his super-low sprint position on the WorldTour stage, we’ve become accustomed to the 24-year-old sprinting in such fashion. But is the position really as fast as it looks?
In the past few months, two research papers about Ewan’s sprint position have sought to answer that very question. The papers come from different research groups on opposite sides of the globe. Both groups were working on the problem at the same time, each without knowledge of the other.
The two groups — one from The Netherlands, one from Australia — used different investigation techniques but, somewhat reassuringly, arrived at remarkably similar results. As it turns out, Caleb Ewan’s low sprint position is more aerodynamic than a regular sprint position, and considerably so.
Most riders tend to give little thought to their position while sprinting. It’s not a discipline that necessarily lends itself to a thoughtful approach — for most riders it’s about finding the position they can generate the most power in, and then mashing away with all they’ve got.
But there are gains to be had for those that take a more analytical approach to their sprinting.
“Nowadays there are so many fast guys that you need every little advantage you can get and getting aero like that gets you a pretty big benefit,” Ewan told CyclingTips in a January 2016 interview.
In a sprint, wind resistance makes up the vast bulk of the resistive forces a rider will experience. At 54kph, wind resistance accounts for 90% of all resistive forces. At 65km/h, it’s up to 95%. That’s because wind resistance increases as the square of a rider’s velocity (and the power required to overcome that wind resistance increases as the cube of the rider’s velocity). Given that, there’s real benefit in reducing your frontal area and as the two recent studies have shown, getting low is a great way of doing that.
The Dutch study
Dr Bert Blocken and his Eindhoven University of Technology colleagues are no strangers to aerodynamic analysis of cyclists. In 2017 the group attracted considerable media attention with their analysis of the supertuck position Chris Froome used during his daredevil descent of the Col de Peyresourde on stage 8 of the 2016 Tour de France. After that study, and after some analysis of peloton aerodynamics, Blocken and co turned their attention to Caleb Ewan’s sprint position.
“We actually bought a scanner to start doing these kind of studies and we said ‘OK, well maybe we should also focus on the sprint,’” Blocken told CyclingTips. “So I had one of my [postgraduate] students, who is actually doing a PhD in cycling aerodynamics, and we just told him ‘OK, try to imitate Caleb Ewan on a stationary bike’ and so we scanned his body in different positions and then actually did the fluid dynamics calculations.”
At the core of the Dutch study, published in the journal Sports Engineering, was a consideration of two sprint positions: a regular, standing sprint position, favoured by most sprinters; and a lower sprint position, as favoured by Caleb Ewan. To provide several reference points, they also scanned three in-the-saddle positions — “back upwards”, “back horizontal” and “back down”.
After the scans were complete, Blocken and co set about using computational fluid dynamics (CFD) to assess the aerodynamic efficiency of each position.
At its most basic, CFD involves using supercomputers to help solve complex fluid flow problems.
“It can be anything — it can be the process of brewing beer or chemical reactors or wind flow in cities for air pollution but also with the flow around athletes,” Blocken explained. “And actually what [CFD] does is solves the physics equations of motion. But if you apply them to fluids … you get quite complicated equations. And these are too complicated to solve just with a pen and paper.
“You need to do that with supercomputers and calculations that take days, sometimes weeks, sometimes months.”
Blocken and his colleagues found that, compared to the regular sprint position, the “sprint low” position resulted in a 19% lower frontal area — 19% less of the rider’s body in the wind. (Interestingly, the “back horizontal” and “back down” positions created even lower frontal areas, but these are not sprint positions).
Overall, the “sprint low” position led to a 24% reduction in wind resistance. As Blocken notes, “That’s actually a huge number.”
So what does a 24% reduction in wind resistance actually mean in the real world? In their Sports Engineering paper, Blocken and co suggest that a rider’s speed in the “sprint low” position should be about 15% higher than in the regular sprint position.
The Australian study
While the Dutch study used CFD to assess Ewan’s sprint position, the Australian study — published in the International Journal of Sports Physiology and Performance — used a combination of field studies and mathematical modelling.
Headed up by PhD student Paul Merkes, the Edith Cowan University researchers recruited 11 recreational riders who helped collect data by sprinting up and down a 250m section of road north of Perth, Western Australia. The riders all did a familiarisation session, to get used to the experimental protocol and the designated section of road, and then each did two sessions worth of sprint efforts for the study.
In each session the riders “sprinted” within three different speed ranges — 24-26kph, 31-33kph and 39-41kph — each in two directions, and all of these in three different positions: seated, standing, and “forward standing” — the last of those mimicking Ewan’s sprint position. In all the riders did 18 recorded sprint efforts each, per day.
From there Merkes and co used a complex mathematical model — based on a 2006 research paper — to determine the aerodynamic drag of each position.
“During those 18 efforts we measured the power output, we measured their speed, we measured wind velocity, wind direction, direction of the road, the gradient of the road, temperature, humidity … all that kind of stuff,” Merkes said. “That bulk of data we put into a mathematical model which has been validated against a wind tunnel and based off that we can actually calculate the aerodynamic drag or CdA as we call it.”
Merkes and co found found a lower average CdA for the “forward standing” position (0.295) compared to both the seated (0.363) and standing (0.372) positions. According to those numbers, Ewan’s “forward standing” position is 26% more aerodynamic than the regular standing position. It’s a result that’s impressively and satisfyingly close to what Blocken and his colleagues found over in Eindhoven (an improvement of 24%).
From there, Merkes and his colleagues took the sprint power numbers of pro racers — as reported in one of the co-authors’ previous papers — and fed them back into the mathematical model along with the CdA results they’d found earlier. The finding: the lower sprint position should lead to a speed increase of nearly 5kph over a regular position.
“If we use the powers published before and if we use the CdA that we got, that would mean in the forward standing position it will range between 59.7 and 65.8 kilometers an hour,” Merkes said. “The seated position will range between 55.8 and 61.4.”
In calculating how much faster Ewan’s low sprint position is, both Blocken and Merkes are making a big assumption: that it’s possible to generate the same amount of power in the low position as it is in a regular sprint position. It’s not entirely clear this is the case.
“Of course people will argue always ‘Yeah but in this [low] position you can exert less power, and yeah probably that’s true,” Blocken said. “I guess [Ewan’s] power output is probably lower but not to the extent that he could not benefit from the aerodynamic benefit.”
Merkes, meanwhile, is currently undertaking a follow-up study on the power output possible in the super-low sprint position. He says that the position mightn’t reduce a rider’s power as much as expected.
“If you look at the data that we currently have … I still have to do complete analysis on it but it looks pretty good for the [super low] position,” Merkes told CyclingTips. “It’s not that much of a difference. So that will be even more beautiful for the position itself …”
So the lower sprint position is more aerodynamic and therefore faster. So why haven’t all sprinters adopted it like Ewan?
“Sometimes you see that the innovations take a long time,” Blocken opined. “And in this particular case I’m a bit surprised because he indeed is a fantastic sprinter and yeah maybe he needs to win even more races before people really start imitating it.”
There’s also the fact that the low sprint position is far harder to get right than a regular, more-upright sprinting position. It takes work, as Ewan told us back in 2016.
“It’s something I’ve been practising for a little while,” he said. “I went in the wind tunnel a bit over a year ago and we tried some different positions and we found that the [low] position is much more beneficial than riding more upright. You don’t really need to go to the wind tunnel to figure that out.”
Even with training, it’s hard to execute the low sprint when it comes to races. It’s significantly more involved than the regular stand-up-and-mash technique that most employ.
“The hard part is getting your head around it during the sprint,” Ewan said. “All you’re thinking about is getting as much power out as possible. Actually thinking about [your position] during the sprint — the split second that you actually have to get lower as the sprint goes on — that’s the hard part.”
It’s not just that Caleb Ewan’s low sprint position looks faster, we now know that it’s faster. At least for him. Has it made the difference in the sprints he’s won in recent years? It’s hard to say, but given how much of a difference the position makes, it certainly seems possible.
Will we see more riders adopt the position in years to come? That might depend on whether it’s a position that other riders can even get into. Could it be that the super low position is only really accessible for shorter riders like Ewan?
“That’s a question that I get a lot actually and also among guys I ride with myself — ‘I am a big guy I can’t get into that position,’” said Merkes. “But I also tested people up to 1.90m during my study and they were actually pretty good in that position as well.
“It might not be as low [as] if you are that small [as Ewan] but people can definitely go lower than some of the riders are doing now.”
Rider size is one of many things that Blocken and his Eindhoven colleagues have earmarked for future investigation.
“You really have athletes that range quite a lot in size, in length, in terms of body geometry,” Blocken said of the pro peloton. “Can everybody just be in this position? And if they can, for how long? And who can’t, and why not?”
Expect further research in this space in the years to come. In the meantime, if you’re a sprinter and you fancy trying out the position, we don’t blame you. Just be careful, and perhaps take a leaf out of Ewan’s book.
“I usually accelerate more upright and then as my sprint goes on I gradually get lower,” Ewan explained. “[I use the position] more so when I try to maintain my sprint when I’m already out in front. If you get a knock while in that position it’ll end pretty badly.
“When I’m around other riders and close to them I’ll still be low, but not that low.”
[ct_highlight_box_start]Additional content on this subject is available exclusively to VeloClub members via the #general channel on the VC Slack.[ct_highlight_box_end]