Hurdling is a sport in which competitors must leap over a series of 10 barriers called hurdles. The most popular outdoor events are the 110-metre high hurdles for men, 100-metre high hurdles for women and 400-metre intermediate hurdles. High hurdles are 107 centimetres, intermediate hurdles are 91 cm and low hurdles are 76 cm high. In the women's 100-metre hurdles, the height is 84 cm.
At all distances for men up to and including the 110 m hurdles, the first hurdle is 13.72 m from the starting line and the remaining hurdles are 9.14 m apart; the distance from the last hurdle to the finish line is 14.02 m. For women, the distances are 13 m to the first hurdle and 8.5 m between hurdles. That includes the 55/60 m in door hurdles.
At distances over 110 m but not exceeding 200 m, the first hurdle is 18 m from the starting line and the remaining hurdles are 18 m apart. At 400 m, the first hurdle is 45 m from the starting line and the remaining hurdles are 35 m apart.