The 400 metres hurdles is a track and field hurdling event. The event has been on the Olympic athletics programme since 1900 for men and since 1984 for women.
On a standard outdoor track, 400 metres is the length of the inside lane once around the stadium. Runners stay in their lanes the entire way after starting out of the blocks and must clear ten hurdles that are evenly spaced around the track. The hurdles are positioned and weighted so that they fall forward if bumped into with sufficient force, to prevent injury to the runners. Although there is no longer any penalty for knocking hurdles over, runners prefer to clear them cleanly, as touching them during the race slows runners down.
The best male athletes can run the 400 m hurdles in a time of around 47 seconds, while the best female athletes achieve a time of around 53 seconds. The current men's and women's world record holders are Kevin Young with 46.78 seconds and Yuliya Pechonkina with 52.34 seconds. Compared to the 400 metres run, the hurdles race takes the men about three seconds longer and the women four seconds longer.