• Team Sky's Chris Froome at the 2015 Vuelta Espana (Getty) (Getty Images)Source: Getty Images
Long awaited data from physiological tests initiated by Chris Froome in hopes of quelling ongoing doubt over his two Tour de France victories have revealed he has the physiology of a Grand Tour winner.
4 Dec 2015 - 1:27 PM  UPDATED 5 Dec 2015 - 8:15 AM

Froome came under sustained pressure this summer when many within and outside the sport continued to express doubts about his career rise and subsequent performances. 

A narrative of the results published in Esquire magazine online revealed that Froome has the physiological capacity required to win the Tour and that his performances over the past two seasons can be largely attributed to weight loss over the course of his recent career.

“The engine was there all along,” Jeroen Swart, sports physician and exercise physiologist at the University of Cape Town said. “He just lost the fat.”

Testing took place at the GlaxoSmithKline Human Performance Lab in London shortly after Froome had claimed his second Tour title and included two sub maximal efforts plus a maximal effort to determing potential VO2.

Froome arrived at the lab weighing 69.9 kilograms, three kilograms heavier than his 2015 Tour weight - 61.5 as lean mass and 6.7 as fat (9.8 per cent).

Compared to similar testing taken in July of 2007, when Froome was eight kilograms heavier with almost twice the body fat, it revealed a physiological consistency that Swart described as "striking."

Once his efforts were further analysed it established Froome was at a level that matched those of a Tour de France winner, with a V02 and power outputs to match.

“Chris’s peak power is 525 watts, which corresponds to 7.51w/kg: a massive figure,” Swart said. “But the interesting thing is that the (sustained) figure of 6w/kg — which is basically what he produced in the lab — is 79.8 per cent of his peak power. That’s a completely reasonable percentage.”

The question now for Froome is if this will this be enough to silence the doubters.



"Natural ability is only one piece of the puzzle of what it takes to win an event like the Tour de France," Froome said on his website.  

"I have always prided myself on my work ethic, dedication and perseverance but without the opportunities and support from Team Sky and Team GB I would not be where I am today.  Team Sky's belief in my ability, structured coaching and attention to detail have given me the platform to maximise my potential.

" I am proud to ride for a team that has shown that you can win the biggest bike races in the world clean.  I can’t wait to start racing next year, to challenge for a third Tour de France title and, hopefully, to ride for Team GB in Rio 2016."

Frederic Grappe, performance director at the French team FDJ who helped France's Thibaut Pinot finish third in the 2014 Tour, told Reuters that the best way to assess Froome's performance would be to release his power output data over the years.

"The tests are a step in the right direction but it's not accurate enough," Grappe said.

There was one indicator, however, that suggested Froome is not a donkey turned into a race horse: the "VO2 max", which is the maximum rate of oxygen consumption. The higher the reading, the fitter the athlete. 

"One thing is sure, his VO2 max suggests he has the engine to achieve what he's achieved," Grappe said.

Froome's VO2 max was measured at 84.6 ml/kg/min, equivalent to 88.2 when adjusted to his Tour de France weight.

"It is possible that it is even higher because, very often, the numbers we have from outdoor tests are higher than the ones conducted in labs."

But the Frenchman said more could have been done to silence the doubters.

"We don't have a lot of data," he said. "For instance we don't have the gross efficiency, which is key in determining the profile of a rider."

The Journal of Science and Cycling defines gross efficiency as the "ratio of work generated to the total metabolic energy cost".

Another much debated figure during the 2015 Tour was Froome's power - the rate at which he can expend energy - and power-to-weight ratio.

All teams use power meters to assess their riders' performance, and some experts say their data can show that a rider is cheating. Froome calls them "clowns", however, and his Sky team's manager Dave Brailsford says it is "pseudo-science".

One of them, Antoine Vayer, a former coach at the Festina team, which was at the heart of the Tour's 1998 doping scandal, believes it is possible to determine the maximum power that can be achieved without doping.

Froome's tests show that he can produce 419 Watts for "20-40 minutes", which, for Vayer, puts him in the 'suspicious' zone.

"This figure means little because we don't know whether it's the power he produced for 20 or 40 minutes. And you usually lose one Watt per minute after 20 minutes," said Grappe, who believes a power passport for all riders would help detect doping, just like the blood passport already in use.

"If your power metre is well calibrated, you have landmarks," Grappe said during the 2015 Tour. "The guy who has a well-established profile and beats his record by 10 per cent ... you know something is wrong."