"All my athletes took it," Victor Conte said recently. "It is bigger than creatine."

Conte was the owner of the BALCO laboratory in San Francisco, the focus of the largest doping scandal in recent years, which put an end to the career of former athletics stars such as Marion Jones.

Viagra dilates blood vessels to take more blood to the penis and thus improve a man's sexual performance. However, experts think the same process takes more oxygen and nutrients to muscles and can be a non-negligible aide in explosive disciplines like sprinting.

"Each time there is a seizure of banned drugs you can be sure that there's Viagra and Cialis found as well," said Christiane Ayotte, head of a laboratory in Montreal, the city where the World Anti- Doping Agency (WADA) has its headquarters.

Like Viagra, Cialis is used to treat erectile dysfunction. According to some experts in sport, its use helps performance at high altitude and with high pollution.

Beijing, the city where the 2008 Olympics are set to be held in August, features significant pollution levels, to the point that Ethiopian Haile Gebrselassie declined to run the marathon there.

"The pollution in China is a threat to my health," said the athlete who suffers from asthma.

Viagra has a great advantage for sports professionals: it is legal, it is not a banned substance. Ayotte noted that Viagra and Cialis are regularly found in sportsmen's urine.

"WADA monitors this substance, as it does with many other substances, and is currently funding a research project on the performance-enhancing potential of Sildenafil (Viagra) at various altitudes," WADA communcations manager Frederic Donze told Deutsche Presse-Agentur dpa.

"It is a WADA decision with which the IOC has nothing to do," the German Thomas Bach, vice president of the International Olympic Committee (IOC) told dpa.

However, WADA processes are slow. The world anti-doping code agreed upon in Madrid in November 2007 is only set to go into force on January 1, 2009, and the project led by Professor Kenneth W Rundell at Marywood University in the US state of Pennsylvania is not expected to present its conclusions before the end of this year.

The effects of Viagra in high-performance sports have been the object of debate for a long time.

"Scientifically, the only proof that Viagra improves sports performance happened at high altitude. That is why it was decided not to include it in the list," the Brazilian Eduardo de Rose, president of the medical commission of the Pan-American Sports Organization (PASO), told dpa.

"You will hardly get to play a football match on Mount Everest," he graphically concluded.

Such an effect at high altitude led Israel to study giving its Air Force pilots pills similar to Viagra, so that they perform better on board their fighter planes. In turn, a group of Argentine scientists proved that hamsters that have taken Sildenafil can recover 50 per cent faster from jet-lag after a long flight.

Scientists cannot quite agree on the pill's effect on sportsmen, although it seems clear that at significant altitude it improves performance considerably.

A study carried out two years ago showed improvements of up to 15 per cent in half the cyclists who took the drug before a high-altitude race.

At sea level it has no effect. However, many do not seem to care: Roger Clemens, pitcher of the New York Yankees who is currently under investigation for perjury, reportedly always had Viagra in his locker.

The father of Italian cyclist Andrea Moletta, suspended in May by the Gerolsteiner team under suspicions of doping, was found with 82 Viagra pills - hidden in toothpaste tubes - in his possession during the Giro d'Italia.

And yet sportsmen are human, and condoms often run out in Olympic Villages. Moreover, there could be other reasons for Viagra's popularity: to compensate for the sexual impotence that is often associated with hormone abuse, or to use it as a party drug, mixed with alcohol and other substances.

However, while the sports world decides whether or not the blue pill constitutes doping, it is still worth being cautious about what one takes.

In September 2007, British authorities found a Chinese businessman who had brought into the country pills that were three times more powerful than the "official" Viagra and were a real danger for anyone with heart problems.

The pills had been made in the Chinese province of Henan. Its capital, Zhengzhou, is just 1,000 kilometres away from Beijing.

(DPA - expatica July 2008)