Michael Phelps waves after receiving his gold medal in the men's 200-meter butterfly at the U.S. Olympic swimming trials in Omaha on Wednesday. He described it as the hardest swim of his career. With the victory, he qualified for his fifth Olympic Games, something no other male American swimmer has ever done. Orlin Wagner/AP hide caption

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Researchers studying brains want to know what's happening in an area called the premotor cortex — the place in the brain that gears up for something the body is about to do, like swimming. Above, Michael Phelps dives off the starting blocks in the final heat of the men's 400-meter individual medley during the 2012 U.S. Olympic Swimming Team Trials in Omaha, Neb., on June 25. Jamie Squire/Getty Images hide caption

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How You Move Your Arm Says Something About Who You Are

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