LONDON • British cyclist Chris Froome said yesterday that tests he took after winning the Tour de France proved that he does not use performance-enhancing drugs. But at least one rival coach said the results would not silence the doubters.

The tests were carried out at the GlaxoSmithKline Human Performance Lab in London in August, a few weeks after the Tour. 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 this year.

During this year's race, he was accused of doping by former riders, reporters and fans. The Tour 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.

"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 French team FDJ, said 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," he added.

One indicator, however, 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. "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," Grappe explained.

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 this year's 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".

REUTERS