Cycling:Lance Armstrong has confirmed his retirement - this time for good - six years after winning the last of his seven Tour de France titles.
His retirement ends a comeback effort that failed to produce an eighth title or diminish talk that performance-enhancing drugs assisted his rise to the top.
The 39-year-old Texan returned to competitive action in 2009 following a three year hiatus, partly in a bid to resurrect his career and partly to take his global fight against cancer - from which he suffered in 1998 - to a new level.
But two more tilts at Le Tour garnered only a third place behind then-team-mate Alberto Contador, before a troubled race last year saw him finish 23rd.
"I can't say I have any regrets. It's been an excellent ride. I really thought I was going to win another tour," Armstrong said about his comeback.
"Then I lined up like everybody else and wound up third. I have no regrets about last year, either. The crashes, the problems with the bike - those were things that were beyond my control."
Armstrong became one of the most controversial figures in the evolving battle against doping in sports. He claims to be the most-tested athlete on the planet during his career. Armstrong came back clean every time, and vehemently denies ever using performance-enhancing drugs.
Even so, he remains shadowed by a federal investigation into the sport launched last year following accusations by former team-mate and disgraced 2006 Tour champion Floyd Landis, that Armstrong used drugs and taught other riders how to beat testing.
"I can't control what goes on in regards to the investigation," he added. "That's why I hire people to help me with that. I try not to let it bother me and just keep rolling right along.
"I know what I know. I know what I do and I know what I did. That's not going to change."
He now plans to devote himself "full time" to his family and leading his cancer research foundation.
"My focus now is raising my five children, promoting the mission of Livestrong and working with companies in the battle against cancer,” Armstrong added.
Armstrong had planned to compete in the Tour of California and other US races this year although he has been troubled by a knee injury since December.
He had already ruled out racing in the Tour de France again and had said January's Tour Down Under in Australia would be his last international race.