Hurdling is the act of jumping over an obstacle at a high speed or in a sprint. In the early 19th century, hurdlers ran at and jumped over each hurdle (sometimes known as 'burgles'), landing on both feet and checking their forward motion. Today, the dominant step patterns are the 3-step for high hurdles, 7-step for low hurdles, and 15-step for intermediate hurdles. Hurdling is a highly specialized form of obstacle racing, and is part of the sport of athletics. In hurdling events, barriers known as hurdles are set at precisely measured heights and distances. Each athlete must pass over the hurdles; passing under or intentionally knocking over hurdles will result in disqualification.
Accidental knocking over of hurdles is not cause for disqualification, but the hurdles are weighted to make doing so disadvantageous. In 1902 Spalding equipment company sold the Foster Patent Safety Hurdle, a wood hurdle. In 1923 some of the wood hurdles weighed 16lbs each. Hurdle design improvements were made in 1935, when they developed the L-shaped hurdle. With this shape, the athlete could hit the hurdle and it will tip down, clearing the athlete's path.The most prominent hurdles events are 110 meters hurdles for men, 100 meters hurdles for women, and 400 meters hurdles (both sexes) – these three distances are all contested at the Summer Olympics and the World Athletics Championships. The two shorter distances take place on the straight of a running track, while the 400 m version covers one whole lap of a standard oval track. Events over shorter distances are also commonly held at indoor track and field events, ranging from 50 meters hurdles upwards. Women historically competed in the 80 meters hurdles at the Olympics in the mid-20th century. Hurdles race are also part of combined events contests, including the decathlon and heptathlon.
In track races, hurdles are normally 68–107 cm in height (or 27–42 inches), depending on the age and sex of the hurdler. Events from 50 to 110 meters are technically known as high hurdles races, while longer competitions are low hurdles races. The track hurdles events are forms of sprinting competitions, although the 400 m version is less anaerobic in nature and demands athletic qualities similar to the 800 meters flat race.
A hurdling technique can also be found in the steeplechase, although in this event athletes are also permitted to step on the barrier to clear it. Similarly, in cross country running athletes may hurdle over various natural obstacles, such as logs, mounds of earth, and small streams – this represents the sporting origin of the modern events. Horse racing has its own variant of hurdle racing, with similar principles.