OK, we all knew Lance has a big heart -- literally, it's 20% larger than yours -- but did you know Andy Roddick had a flexible torso? Here's a look at the poking and prodding of elite athletes.

While genetics is only one part of the formula for greatness, scientists agree that in order to be truly dominant, an athlete has to be — to some degree — a genetic freak. Olympic champion swimmer Michael Phelps, for instance, propels himself through the water with a pair of feet that operate like flippers. Not only are they large (size 14), they’re so outrageously flexible that the swimmer can lie down flat on his back, legs outstretched and, while doing so, touch the tips of his toes to the floor. “He’s not your average bear,” says his coach, Bob Bowman.

Andy Roddick, owner of the fastest recorded tennis serve (155 miles an hour), owes much of his power to the unusual flexibility of his ribs and spine. Bob Prichard, president of Somax Sports, a California clinic that works with top athletes, says Roddick’s ability to arch his back increases the effective external rotation of his arm to 130 degrees, 44 percent better than the average tennis pro.

Mia Hamm, the now-retired soccer star, may owe some of her famous stamina to a genetic anomaly. In a test run by the Gatorade Sports Science Institute, she produced less than one liter of sweat an hour, 25 percent to 50 percent less than normal. Bob Murray, the institute’s director, says this trait allows Hamm to perform for longer stretches without having to stop to guzzle fluids.