Hurdles is the term given to a diverse set of track disciplines, a reference to both a series of individual sprint competitions as well as comprising a part of larger, multi-sport events. The common element to any hurdles competition is the barrier itself, an upright obstacle 36 in (0.9 m) high for men, 30 in (0.75 m) high for women, set at evenly spaced intervals on the race course.
In outdoor track and field competition, the hurdles are run at distances of 110 m and 400 m for men and 100 m for women. The 110-m hurdles is also one of the ten events that comprise the decathlon; the 100-m hurdles is the corresponding event in the women's seven event heptathlon. The other traditional Olympic event that includes the hurdles is the men's 3,000-m steeplechase, where a water barrier and hurdles must be cleared by the competitors in a 7.5-lap course.
Hurdling is an extremely demanding sport at every distance, as it requires the athlete to run as explosively as the sprinters, while incorporating the finesse and the technique required to fluidly clear each barrier. The training techniques for all manner of hurdling place significant emphasis on plyometrics training to build and maintain lift as the runner approaches each hurdle, and maximum flexibility through the hips and pelvis to optimize each clearance, as well as to reduce the risk of injury.
Hurdling success is synonymous with running efficiently. Every barrier that is either knocked down by the runner or otherwise clipped by a runner's foot or leg is an impediment to a fast time. Conversely, bounding high over each hurdle results in the runner covering a greater than optimum distance to the finish line. Hurdlers in every category spend considerable amounts of training time in practicing the precise coordination of their footwork and leg action necessary to approach each hurdle with speed and efficiency. As an example, most male hurdlers in the 110-m event use seven or eight strides to reach the first hurdle, and after clearing it, take three strides exactly between the remaining hurdles to the finish line. With this approach, the runner takes shorter strides at a faster cadence to propel forward. In addition to maintaining a precise stride pattern, the hurdler seeks to be as low over the barrier as possible without striking it, a position that keeps the runner's center of gravity as close as possible to the ideal sprinting position, thus maximizing the forward speed.