400 metres hurdles to 400 metres, or one lap of the stadium, and the number of hurdles was reduced to ten. The official height of the hurdles was set to 91.4 cm (3 feet) for men and 76.20 cm (2 ft, 6 inches) for women. The hurdles were now placed on the course with a run-up to the first hurdle of 45 metres, a distance between the hurdles of 35 metres each, and a home stretch from the last hurdle to the finish line of 40 metres. The first documented 400 m hurdles race for women took place in 1971. The International Association
United States at the 2013 World Championships in Athletics Jennifer Simpson (1500m), Lashinda Demus (400m hurdles), and Brittney Reese (long jump) on the women's team. 2012 Diamond League champions Charonda Williams (200m), Dawn Harper (100m hurdles), Chaunte Lowe (high jump) and Reese Hoffa (shot put) were also automatic qualifiers to the team. World record holder Aries Merritt was also a Diamond League champion in 2012, but a country is only allowed one bye into the championships. The bye into the 110m hurdles was already taken by Jason Richardson, so Merritt had to qualify by placing in the championships. Decathlon Heptathlon United States at other World Championships in 2013 United