Athletes who compete in hurdle races need a sprinter's speed as well as the technical ability to clear the hurdles. Runners typically take seven to eight strides before hurdle one, then use a three-stride pattern between the rest, according to Brian Mac, performance coach for UK Athletics. The trailing leg, which initially drives a runner's body at the hurdle, also must sweep over the hurdle rather than around it. The International Association of Athletics Federations is the worldwide governing body for track and field events, including hurdles. Associations at the national, state and local level generally follow IAFF rules, though modifications can exist.
The placement of the hurdles depends on the length of the race and the sex of the athlete. Ten hurdles are used in the 100-meter, 110-meter and 400-meter hurdle races. Men run the 110 races with 9.14 meters between hurdles and women run the 100 races with 8.5 meters between hurdles, according to IAAF rules. Both men and women run the 400 races with 35 meters between hurdles. The same set-up applies to youth divisions. Hurdles are 106.7 centimeters tall for men and 83.8 centimeters tall for women in the 110 and 100 races. Hurdles are 91.4 centimeters tall for men and 76.2 centimeters tall for women in the 400 races. The National Collegiate Athletic Association requires hurdles to be placed in all lanes but allows racers to run only in alternate lanes. The IAAF and USA Track and Field do not have this requirement. However, neither organization prohibits this set-up, which is common practice, according to USATF. The set-up limits races to four runners per heat on most tracks.
Runners who deliberately knock down a hurdle are disqualified under IAAF rules. Runners who knock over a hurdle accidentally are not disqualified. Whether the hurdle was downed deliberately is left to the referee's judgment. The National Federation of High Schools had a similar rule until 2010. Now, if a runner knocks down a hurdle with her hand she is disqualified, according NFHS rules. Under the old rules, a hurdle intentionally knocked down by a runner's foot also led to disqualification.
In all levels of competition, runners are required to attempt to clear each hurdle. A hurdler who runs around a hurdle is automatically disqualified. Runners who trail a leg or foot below the horizontal plane of the hurdle's top at the moment of clearance also are disqualified, according to IAAF rules. The international organization's rules also require runners to stay in their own lane throughout the race.