Men start from blocks and negotiate ten 3ft 6in (107cm) hurdles spread over a 110m straight.
A reaction time – measured by sensors in the starting pistol and on the blocks – of less than 0.1 is deemed a false start and runners will be recalled, and the responsible athlete disqualified.
Once the race is underway there are 13.72m to the first hurdle, 9.14m between hurdles thereafter, and 14.02m from the final hurdle to the finish.
The hurdles are knocked down easily if touched, which allows the athlete to continue the race even if he collides with them. But a runner can be disqualified if he steps out of his designated lane.
Wooden barriers were placed along a stretch of 100 yards in England during the 1830s. Oxford and Cambridge universities developed the event, increasing its distance to 120 yards (109.7m), which in turn was rounded up to 110m by the French in 1888.
Did you know
America’s Alvin Kraenzlein, the 1900 Olympic champion, was the first to use the current running style, i.e. taking the first hurdle on the run with the upper body lowered, and taking three steps between hurdles.
Americans have won no less than 19 of the Olympic titles. Cuba and Great Britain also boast strong overall records, while China is an emerging nation.