At the Beijing 2008 Olympics, in the 100 meter butterfly, multi-gold medalist Michael Phelps won by one one-hundredth of a second. While his competitor, Milorad Cavic glided in the water, Mr. Phelps powered a last half-stroke, which made all the difference. A top-of-the world champion doesn’t glide. And he never gives up. Usain Bolt of …