5. Herschel Walker
When Herschel Walker walked away from the NFL at age 35, after 13 years of highlight-reel runs and hard-fought touchdowns—not to mention one of the most dominating college careers of all time—most people assumed he’d rest his body and retire to the broadcasting booth.
But the All-Pro running back couldn’t stay sedentary for long, and instead emerged in his 40s kicking ass in an entirely different, but equally demanding sport: mixed martial arts.
Walker has won two pro MMA bouts to date—chalk that up to his brutal daily regimen of 3,500 situps, 1,500 pushups, and an 8-mile run—and recently indicated that he’s even flirting with returning to the gridiron … at age 50.
Take that, AARP membership.