The 100 metres, or 100-metre dash, is a sprint race in track and field competitions. The shortest common outdoor running distance, it is one of the most popular and prestigious events in the sport of athletics. It has been contested at the Summer Olympics since 1896 for men and 1928 for women. The reigning 100 m Olympic champion is often named "the fastest man/woman in the world".On an outdoor 400 metres running track, the 100 m is run on the home straight, with the start usually being set on an extension to make it a straight-line race. Runners begin in the starting blocks and the race begins when an official fires the starter's pistol. Sprinters typically reach top speed after somewhere between 50–60 m. Their speed then slows towards the finish line.The 10-second barrier has historically been a barometer of fast men's performances, while the best female sprinters take eleven seconds or less to complete the race. The current men's world record is 9.58 seconds, set by Jamaica's Usain Bolt, while the women's world record of 10.49 seconds set by American Florence Griffith-Joyner in 1988 remains unbroken.The 100 m (109.361 yards) emerged from the metrication of the 100 yards (91.4 m), a now defunct distance originally contested in English-speaking countries. The event is largely held outdoors as few indoor facilities have a 100 m straight.