Jamaica's Usain Bolt, left, crosses the finish line ahead of Ryan Bailey of the United States in the men's 4x100-meter relay final during the athletics in the Olympic Stadium at the 2012 Summer ... more 

Jamaica's Usain Bolt, left, crosses the finish line ahead of Ryan Bailey of the United States in the men's 4x100-meter relay final during the athletics in the Olympic Stadium at the 2012 Summer Olympics, London, Saturday, Aug. 11, 2012. Jamaica set a new world record with a time of 36.84 seconds. (AP Photo/David J. Phillip) less