British cyclist Chris Froome says tests he took after winning the Tour de France prove he does not use performance-enhancing drugs - although at least one rival coach believes they won't silence the doubters.
The tests were carried out at the GlaxoSmithKline Human Performance Lab in London in August, a few weeks after the Tour, and the results he released suggest that a huge weight loss could help explain his rapid rise from 2007, when at 22 he was a rough diamond at best, to Tour champion in 2013 and 2015.
During this year's race, Froome was accused of doping by former riders, reporters and fans of a race that has been beset by doping scandals for almost 20 years.
Some fans even threw urine at Froome, who has always vigorously denied doping, as the race's atmosphere turned sour.
"The figures make one thing very clear to me, if I ever needed any reminder," Froome said in a statement on Friday.
"Natural ability is only one piece of the puzzle of what it takes to win an event like the Tour de France. I have always prided myself on my work ethic, dedication and perseverance."
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," said Grappe.
Froome's VO2 max was measured at 84.6 ml/kg/min, equivalent to 88.2 when adjusted to his Tour de France weight.
But Grappe 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."
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".
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 to 40 minutes", which, for Vayer, puts him in the "suspicious" zone.
Grappe believes a power passport for all riders would help detect doping - just like the blood passport already in use.
"The guy who has a well-established profile and beats his record by 10 per cent ... you know something is wrong," the Frenchman said during the 2015 Tour.
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