The Twitterverse is buzzing after Lance Armstrong announced that he is retiring, and this time, he says, he means it. The 39-year-old cyclist and cancer survivor has won a record seven Tour de France titles. Armstrong first retired in 2005 in order to promote the Livestrong Global Cancer Campaign. But he returned to the sport in 2008 in an attempt to win his eighth title and to dispel persistent rumors that he had used performance-enhancing drugs. In the 2009 Tour de France, he placed third. In a tweet, Armstrong thanked his fans for all their support and declared "Onward!"