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When Michael Phelps is out of the water, he towers over mere¹ non-Olympic mortals. Then he slips into the pool, and makes record-breaking speed seem effortless. His height, it turns out, is no accident. According to research published in The Journal of Experimental Biology, winning athletes are getting taller, more slender, and yet heavier in comparison to the normal population.

Since 1900, the average person’s height has gone up by about two inches. But winning swimmers are four and a half inches taller than their old-time counterparts.

Researchers applied² mathematical models of animal locomotion³ to show why height gives them a competitive advantage. Coaches have said in the past that swimmers should lift their bodies out of the water because air has less drag. But researchers showed that larger bodies fall faster and more forward in the water and create a larger wave that helps push them ahead.

The authors suggest that in the future we might need weight classes for all sorts of sports, not just boxing or wrestling. That might give one of the shorter guys a chance to win an Olympic swimming event even with Michael Phelps in the race.