Katie Ledecky sees a world record in the 1,500. (Michael Dalder / Reuters)

Katie Ledecky, the 16-year-old Olympic champion from Bethesda, Md., blazed to a world record in the 1,500-meter freestyle race in the world swimming championships today in Barcelona, Spain.

(Michael Sohn / AP) (Michael Sohn / AP)

Ledecky set a record of 15 minutes, 36.53 seconds, smashing the previous mark set  15:42.54 set by Kate Ziegler in 2007. The medal is the second this week for Ledecky, who won the 400 freestyle on Sunday.

Ledecky caught Lotte Friis of Denmark, who led for much of the race, with a late burst. Friis finished second in 15:38.88, which also bests Ziegler’s mark. New Zealand’s Lauren Boyle was third in 15:44.71

“It was really tough, my hardest race ever,” Ledecky said afterward. “I knew we were going pretty fast and I figured that whoever came out on top was probably going to get the world record.

“I had to be careful not to push it too early or push it too late and just touch the wall first.”

Ledecky’s comment reveals a sound strategy, one her coach was coy about going into the race.

“There might be some time goals but we’ll keep them to ourselves for now,” Bruce Gemmell said on FINA.org.  “She’ll get up and she’ll race and she’ll have fun doing it and grit her teeth and go. Katie swims the way Katie swims, she likes to go out fast and stay that way.”

Ledecky made a national name for herself last summer when she won gold in the 800-meter freestyle in the London Olympics.

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