Tour de France leader Alberto Contador on Thursday evaded questions about suggestions by former U.S. cycling star Greg LeMond that he might be doping, according to several media reports.

On Thursday, after winning the individual time trial in Stage 18 to solidify his stranglehold over teammate Lance Armstrong and the rest of the field, Contador refused to answer a series of questions about the article written by LeMond — a three-time winner of the Tour — for the French newspaper Le Monde.

In the article, LeMond wrote, "Never has a rider in the Tour climbed so fast," in reference to the 5.1-mile climb at an average gradient of 7.5 percent to the summit of Mount Verbier in the Pyrenees during Stage 15 on Sunday. Contador needed only 20 minutes and 55 seconds to climb it.

"How do you explain such a performance?" LeMond wrote. "According to the last information published by former Festina trainer and specialist in performance Antoine Vayer in [the French newspaper] Liberation, the Spanish rider would have needed a VO2 max (consummation of oxygen) of 99.5 ml/mn/kg to produce such an effort.

"To my knowledge this figure has never been achieved by any athlete in any sport. It is a bit like if you took a nice Mercedes out of the car showroom, lined it up on a Formula 1 circuit and won the race. There is something that is wrong. It would be interesting to know what is under the bonnet.

"Can a rider racing on water achieve such speed in climbing and strength to Verbier? Perhaps. If the studies by Antoine Vayer are correct, Alberto Contador will be the first human to achieve such a level of performance ...

"The charge to Alberto Contador is to prove that he is physically capable of achieving this prowess without falling back to the use of performance enhancing products. Because of the recent history of our sport, doubt is rigorous. It should lead us to question extraordinary performances. That is why the sceptic I have become wants to ask Alberto Contador to convince us."

When asked to respond to the article, Contador paused, would not answer and said "Otro pregunta (next question)."

Two questions later, he again refused to answer a question about LeMond's article, then also refused to reveal what his VO2 maximum is.

It wasn't the first time Contador has faced doping suspicions. Two years ago, after winning one of the most drug-scarred Tours ever, Contador was accused of doping by German biochemist Werner Franke. Franke said he had obtained documents from the Operation Puerto doping investigation in Spain which purportedly showed that Contador had taken a testosterone booster and an asthma product.

In 2006, Contador's former team Liberty was disqualified from the race after he and four other teammates, as well as the team director and doctor, allegedly were linked to Operation Puerto.

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