Katie Ledecky breaks American, NCAA marks in 500-yard freestyle

Five-time Olympic gold medalist Katie Ledecky broke her own American and NCAA records in the women's 500-yard freestyle Thursday night at the Pac-12 championships in Federal Way, Washington, dominating the rest of the field in 4 minutes, 25.15 seconds.

A freshman at Stanford, Ledecky, 19, finished more than 10 seconds ahead of the runner-up, Cardinal teammate Katie Drabot.

Ledecky cut more than a second off her previous record of 4:26.46, which she set in November at the Ohio State Invitational.