Usain Bolt has wowed the world once again. In Beijing 2008 he won both the 100-and 200-meter sprint titles and at the London 2012 Olympic games he has done it again. He's the first man to ever defend his 200-meter Olympic title and becomes the first to win the 100 and 200 in back-to-back Games. How does he do it? This video from NBC Learn and the National Science Foundation explains the biomechanics of Bolt.