At the age of 41, Jack LaLanne swam from Alcatraz to shore handcuffed. He repeated the feat at 60, this time towing a 1000 pound boat while shackled.
Jim Fixx, the man credited with starting the fitness revolution and demonstrating the health benefits of jogging, died of a heart attack while jogging.
A fitness trainer intentionally gained over 70 pounds to better understand the plight of his overweight clients. Then lost it all again six months later.