Team Sky reveal Froome’s Tour de France data from stage 10

Kerrison: "With great power comes great responsibility"

Team Sky has revealed some of Chris Froome’s Tour de France performance data in an attempt to respond to the stream of estimates and innuendo from external observers and data experts.

Head coach Tim Kerrison sat in on the team’s press conference with team manager Dave Brailsford, Geraint Thomas and Chis Froome. After a series of questions about the race and the recent polemics, Kerrison revealed data for Froome’s performance on the La Pierre-Saint-Martin climb on stage 10, the first mountain stage in the Pyrenees, where Froome distanced his rivals as they struggled in the heat after the first rest day.

“We’re not going to get caught up in endless debate. We’ll give you info, carry on racing and then address it after the Tour if necessary,” Brailsford said before handing over to Kerrison.

“I just think that in particular what France2 did by putting out that big headline of the 7 watts/kg with a picture of Lance Armstrong, and I think Jan Ullrich, was so wildly wrong on so many levels. We thought we should correct that and give concrete facts and evidence, so hopefully people will judge for themselves. That’s what drove my decision,” Brailsford added.

Froome stayed silent as Kerrison reeled off the numbers but said briefly that he agreed with the publication, even if he suggested that it would change little.

“I’ve never had an issue with it,” Froome said.

“From the team’s point of view, I feel it’s our competitive advantage, so sharing a file here and there… people know that one of my most significant power files is already out there from Ventoux. So what will it change?”

Watts, VAM, V02 Max and heart rates

Tim Kerrison usually stays out of the spotlight but seemed at ease as he read off a series of power numbers and Froome’s heart rates.

“We have a lot of data on our riders and the way we apply and use it, we see that gives us a competitive advantage. As in most industries, knowledge and intelligence is giving a competitive advantage,” he said.

“It’s difficult to indicate the exact start of the climb, so I’ve analysed the last 15.3km, which is an effort of about 41 and a half minutes.

“For that 41:30, Chris had an average power of 414 watts, which gives a 1602 VAM. We know power Osymetric chainrings (used by Froome) over estimate power by about 6 per cent. That’s why it has to be considered when interpreting Chris’ power. With his weight hovering around 67.5kg that gives a correct power of 5.78 watts per kilo.”

Kerrison warned against making assumptions with the data.

“Going from that to making some assumptions about Chris’s physiology requires a lot of assumptions about his relative aerobic and anaerobic consumptions on the climb, the percentage his V02 max that can be sustained and his efficiency as a rider. There’s also a margin of error in each estimates that compounds with each one. So to draw any conclusions about his physiology from time or climbing speed alone, there is a high margin of error.”

Kerrison also revealed Froome’s heart rate for the climb. The data that was leaked last week revealed that Froome’s heart rate remained surprisingly constant at around 160 per minute while climbing and attacking on Mont Ventoux in the 2013 Tour de France.

“Chris had a gearing of 52x39 and 11x28, which allows a lowest gear of 38x28 and allows for the high cadence that he does. He averaged 97rpm. His average heart rate was 158. His max heart rate was 174. For Chris that equals his highest heart rate in a Grand Tour, certainly in last few Grand Tours he’s done. It also suggests he arrived relatively fresh into that point of the race and into the climb. Our objective in any Grand Tour is to arrive fresh to sustain a high level of performance. That’s one of the indicators that we use. We saw his maximum dropped over the course of a Grand Tour and its one of the things we aim to prevent. To put that into context, Chris’s maximum heart rate in 2013 was 168 compared to 174 is year and 171 in the 2014 Vuelta compared to 174 this year.”

Kerrison also revealed data about his attack on the climb to La Pierre-Saint-Martin.

“The attack I looked at was a period where power was over 450 watts and it was about a 24 seconds duration. There’s an average power of 556 watts, with a peak power of 929 watts. Again that’s just the power metre and does not include the 6 per cent adjustment (for O-symmetric).”

The highest power that Chris averaged for 10 seconds was 652 watts, which is 60 per cent of his max power. His average speed was 25.3km/h and his maximum speed was 27.7km/h.

“To put that in context, when you look at the four-minute period when the GC contenders were largely still there, the power was 449 watts and the VAM was 1777. Four minutes after the attack, the power was 435 watts. So after that initial attack, Chris’s power was lower than in the four minutes leading into the attack, yet he continued to ride away from Quintana and the others.”

Kerrison revealed that Froome’s power was slightly less on the climb to Plateau de Beille and acknowledged that many factors including gradient, temperature, wind direction and altitude can affect the data, even if the calculations factor in those factors

Responding to questions

Kerrison then responded to several questions about the people who calculated and estimate rider performance data.

“I understand there are people who are curious about performance of the riders and data. But I think people can understand our desire to keep our competitive advantage by not telling everything even if we’ve just told you a lot about the climb.

I do think people, especially scientists, need to ensure the info they share is accurate or at least highlight the assumptions that are made. I certainly wouldn’t tar everyone with the same brush. In the last week we’ve read some well-informed and balanced pieces on the merits on how to estimate physiology and climbing times.”

Kerrison was critical of those who have made different assumptions about Froome’s performances and warned that commentators and scientists have a responsibility for what they say.

“With great power comes great responsibility. If you have the power to influence what millions of people are thinking about a situation, you have the responsibility to make sure that your facts are accurate.”


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