Former cyclist Scott Mercier has gained notoriety for refusing to go on a doping program 15 years ago. Here, Mercier (in blue jersey) rides just ahead of cyclist Chris Horner in 1997. Jed Jacobsohn/Getty Images hide caption

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Lance Armstrong competes in the Ironman Panama 70.3. triathlon in Panama City, Panama. Arnulfo Franco/AP hide caption

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Lance Armstrong, wearing the yellow jersey that identifies the leader in the Tour de France, during the race in 2003. He won that year and six other times. Joel Saget /AFP/Getty Images hide caption

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Lance Armstrong grimaces prior to the start of the third stage of the Tour de France cycling race in Wanze, Belgium, on July 6, 2010. Armstrong said Thursday he is finished fighting charges from the U.S. Anti-Doping Agency that he used performance-enhancing drugs during his unprecedented cycling career. Christophe Ena/AP hide caption

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LaShawn Merritt crosses the finish line first, in the men's 4x400-meter relay at the IAAF World Athletics Championships in Daegu, South Korea, Sept. 2. Once banned for doping, Merritt has been cleared to run in London next summer.

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