There's a well-known saying that age is just a number. Unfortunately , this axiom doesn't always apply when it comes to professional sports. While it's true that athletic careers are getting longer thanks to advances in medicine and science, it's also true human bodies just don't bounce back from aches, pains and stress fractures like they used to when people were young.
Even the mighty Shaquille O'Neal had to concede in his June 2011 retirement announcement that, at 39, "Father Time has caught up with Shaquille O'Neal."
Still, there are many athletes who have refused to go quietly, and who have stayed on the field after conventional wisdom dictated they should hang it up.
|Slideshow: 10 active athletes over 40|
George Blanda played 26 seasons of professional football, not retiring until he was over 48 years old. Segregation stopped Satchel Paige from joining a Major League Baseball team until the league was integrated, when he became a Cleveland Indians rookie at 42 and kept playing until he was 59. And when Gordie Howe stopped playing ice hockey in 1980, he was 52 years old, although he came back for a single game in 1997 at the age of 69, making him the only player to have played in six different decades.
Athletes who are active today have more avenues to extend their playing careers. Orthopedic medicine has come a long way, and advances in nutrition and fitness training make it possible for sports fans to see their favorite athletes participate in aggressive, high-contact sports in their 40s and beyond. If advances in these fields continue, maybe it's not so crazy to think that future generations of sports fans might see football players, hockey players and boxers playing at competitive levels in their 60s and 70s.
Who are 10 notable athletes who are still active after turning 40? There are several pitchers – including Mariano Rivera and Tim Wakefield – and also some footballers, both NFL and soccer variety. Dara Torres represents the Olympics, as does a 70-year-old equestrian. Who else? Click ahead and find out.