Years of success and defiance, then a rapid fall

The Texas-born Armstrong grew up to become an established athlete, including winning several Tour de France stages. But his sporting career ground to a halt in 1996 when he was diagnosed with cancer. He was 25.

He returned to the cycling world, however. His breakthrough came in 1999, and he didn't stop as he reeled off seven straight wins in his sport's most prestigious race. Allegations of doping began during this time, as did Armstrong's defiance, including investigations and a lawsuit against the author of a book accusing him of taking performance enhancing drugs.

He left the sport after his last win, in 2005, only to return to the tour in 2009.

Armstrong insisted he was clean when he finished third that year, but that comeback led to his downfall.

"We wouldn't be sitting here if I didn't come back," he told Winfrey.

In 2011, Armstrong retired once more from cycling. But his fight to maintain his clean reputation wasn't over, including a criminal investigation launched by federal prosecutors.

That case was dropped in February. But in April, the U.S. Anti-Doping Agency notified Armstrong of an investigation into new doping charges. In response, the cyclist accused the organization of trying to "dredge up discredited" doping allegations and, a few months later, filed a lawsuit in federal court trying to halt the case.

In retrospect, Armstrong told Winfrey he "would do anything to go back to that day."

"Because I wouldn't fight, I wouldn't sue them, I'd listen," he said, offering to speak out about doping in the future.