Like any world-class athlete, 18-year-old swimmer Katie Ledecky can swim hundreds of meters and make it look easy.

And, a mere 30 minutes later, she can make it look easy again.

The American won back-to-back races in the 1500-meter and 200-meter individual freestyle events at the FINA World Championships in Kazan, Russia, earlier this month. And she went right on winning.

By the end of the meet, the Washington, D.C., native had swept the entire category of women's individual freestyle races.

The accomplishment makes Ledecky the first swimmer—man or woman—to win the 200-meter, 400-meter, 800-meter, and 1,500-meter individual freestyle races during a single meet.

She broke three world records in the process.

"Insane!" exclaims Michael Joyner, a physiologist at the Mayo Clinic and an expert in human endurance, in an article by Outside Online. "The fact that Ledecky won both long- and short-distance events at the same meet puts her accomplishment on a different level than even what Michael Phelps has done."

At 6'0" and 155 pounds, with "a huge aerobic engine," Ledecky is perfectly built to be a great female swimmer, Joyner said. But it's her form—the efficiency of her movements in the water—that really sets her apart.

Given endurance-sport athletes' tendency to peak in their late-20s or even their early-30s, it looks like Ledecky's best years are yet to come—right after she wraps up a few driver's ed classes and finds time to "sit on the couch sipping milkshakes" after getting her wisdom teeth out.

The recent high-school graduate is at home in Bethesda, Maryland, taking a ‘gap year' off to train for the 2016 Olympics, and plans to enroll at Stanford University next fall.

(READ more at Outside Online) — Photos: Chan Fan and FreedSpirit

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