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100 metres Dash (one hundred metres) is the shortest outdoor sprint race distance in athletics.
The reigning 100 m Olympics Games 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.
Masters 100 metres Dash All-Time World Rankings
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 two 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. A reaction time less than 0.1 seconds 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 reach the runners' ears, and the time it takes for a human to react to it.
For many years a sprinter was disqualified if they were responsible for two false starts individually. However, this rule was allowing some major races to be 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. This rule has led to some sprinters deliberately false-starting to gain a psychological advantage: an individual with a slower reaction time might false start, forcing the faster starters to wait and be be sure of hearing the gun for the subsequent start, thereby losing some of their advantage.
Climatic conditions are a crucial factor for good performances in the 100 m. Air resistance is the primary climatic factor in sprint performances. A strong head wind is very detrimental to performance, while a tail wind can improve performances significantly. For this reason, a maximum tail wind of 2.0 m/s is allowed for a 100 metres Dash performance to be considered eligible for records, or 'wind legal'.
Furthermore, sprint athletes perform better at high altitudes because of the thinner air, which provides less air resistance. While there are no limitations on altitude, performances made at altitudes greater than 1000 m above sea level are marked with an "A".
On April 13, 1996, Obadele Thompson of Barbados ran the fastest 100 m race ever in El Paso,Texas, stopping the clock at 9.69 sec. However, as it was achieved with a tail wind of 5.7 m/s, the record was rejected.