Italian cyclist Riccardo Ricco today was pulled from the Tour de France after he tested positive for the banned substance EPO, a hormone that boosts oxygen levels in the blood and, hence, stamina.

Ricco, 24, is the third cyclist to test positive for EPO use during this year's Tour. Spanish riders Moises Duenas Nevado and Manuel Beltran were both booted after testing positive for the endurance-enhancing drug. Duenas Nevado was expelled yesterday; Beltran tested positive last Friday.

Cyclists have been using EPO to get an unfair competitive advantage since 1998, when customs agents found it and a host of other illicit substances in the possession of a trainer for the Festina cycling team. EPO, like testosterone, human growth hormone and steroids, improves muscle strength and gives riders an unfair boost in endurance. The substance has been used by athletes in track and field, cross-country skiing, and in March, a German billiards player even was caught using it. (Who knew nine-ball could be so exhausting?)

"If [cycling] goes on like this," David Howman of the World Anti-Doping Agency lamented to Reuters about the culture of cheating: "It won't even be a sport anymore."

(Image:  © iStockphoto/wsfurlan)