100 metres

100 m (one hundred metres) is the classic sprints race distance. The reigning 100 m Olympic champion is often named "the fastest man/woman in the world". A distance of 100 yards (91 m) was often run in the past, but this is now obsolete. Indoors, events are normally held over 60 m (sometimes 50 m or 55 m) as few facilities have a 100 m indoor straight.

On an outdoor 400 m running track, the 100 m is run on the home straight: the start being set on an extension to make it a straight line race. Many top level 60 m runners fail to excel at the 100 m. Illegal drug use has been seen by some as a means to gain a competitive edge; in particular, the scandal at the 1988 Summer Olympics when the winner Ben Johnson was stripped of his medal.

Record performances

Major 100 m races, such as at the Olympic Games, attract much attention, particularly when the world record is thought to be within reach. The record has been lowered 10 times since the introduction of electronic timing in 1968, and never by more than 0.05 seconds. The current world record of 9.77 seconds is held by Asafa Powell of Jamaica and Justin Gatlin of the United States. In the women's competition the world record belongs to Florence Griffith Joyner who ran a time of 10.49 seconds in Indianapolis on 16 July 1988.

Start

At the start, some athletes play psychological games such as trying to be last to the starting blocks, although direct intimidation would be considered unsporting. The starter will keep the sprinters in the set position for an unpredictable time of around 2 seconds and then fire the starting gun.

The time between the gun and first kick against the starting block is measured electronically, via sensors built in the gun and the blocks. Anything less than a 0.1 second reaction time is considered a false start. The 0.1 second interval accounts for the sum of the time it takes for the sound of the starter's pistol to propagate through the air and reach the runners' ears, and the time it takes for a human to process the auditory stimulus and react to it.

For many years a sprinter was only disqualified if they were responsible for two false starts. However, this rule was causing some major races being restarted so many times that the sprinters started to lose focus. The new rule is that after one false start, anyone responsible for a subsequent false start is disqualified immediately, though this rule has led to some sprinters deliberately false starting to gain a psychological advantage especially if they're one of the slower starters in the field.

Source: Wikipedia
http://en.wikipedia.org/wiki/Track_and_field