Health & Science

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Why Phelps set so many records

At this year’s Olympics, swimmers set 25 new international speed records, compared with only eight new record times at the 2004 Games in Athens. The talents of Michael Phelps and the other record-breakers are partly responsible, but the depth of the pool in Beijing played a major part in the eye-opening speed of the 2008 Olympics’ swimmers, says New Scientist. It’s a matter of basic physics. The Beijing pool is about 3 feet deeper than pools used at earlier Olympics. That additional depth reduces the drag on a swimmer’s body by extending the distance traveled by the so-called bow wave—the wave that shoots downward and outward from the swimmer’s upper body. A swimmer generates a second wave, known as the stem wave, with his lower body. If the bow wave bounces off the bottom of the pool and comes back to contact the stem wave, the result is drag. Since the Beijing pool is too deep for the bow wave to reflect back on the stem wave, swimmers do not have to contend with some of the usual backward pull, enabling them to swim faster. Experts stress, though, that the pool is within official size limits, so the swimmers fully deserve to be in the record books. “The current spate of swimming records is fair and valid,” says exercise scientist Brent Rushall.

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