100 metres

The 100 metres, often called the 100-meter dash, is a premier sprint race in track and field. It represents the shortest common outdoor running distance in the sport of athletics. Because of its speed and intensity, it is considered a "blue ribbon" event at the Olympic Games. This prestige often grants the winner the unofficial title of the "world's fastest man or woman."

Executing a perfect race requires a strict sequence of technical steps and commands. First, officials give the instruction "on your marks," prompting runners to move to their starting blocks. Next, the command "set" is given to help athletes adopt an efficient starting posture. This position allows them to isometrically preload their muscles, which assists in a faster start. Finally, a race official fires a starter's pistol to signal the beginning. Sprinters then stride forward from the blocks to begin their acceleration.

Race dynamics involve complex physics and psychological elements. High-level meets use electronic sensors in the gun and blocks to measure reaction time. A reaction time of less than 0.100 seconds is classified as a false start. This measurement includes the time for sound to reach the ear and the physical reaction. Rules regarding false starts have changed over time to improve spectator enjoyment. In 2010, the IAAF implemented a rule where any athlete responsible for a false start receives immediate disqualification. This was done to prevent athletes from using false starts to gain a psychological advantage over competitors.

During the middle of the race, sprinters focus on maintaining their velocity. Most runners reach their maximum top speed between 50 and 60 metres. After reaching this peak, athletes typically begin to progressively decelerate toward the finish line. Because success depends on pure athletic qualities and technique, pacing and running tactics do not play a significant role. To determine the winner, officials look for the first athlete whose torso crosses the finish line. The torso does not include the head, neck, or limbs. If the results are too close to see, officials use a photo finish to distinguish the winner.

History shows that the 100 metres has been a staple of international competition for over a century. Men have contested the event at the Summer Olympics since 1896. Women have competed in the Olympic 100 metres since 1928. The inaugural World Championships for this event took place in 1983. While it is usually the shortest Olympic sprint, a men's 60-metre race was briefly contested between 1900 and 1904.

Performance in the 100 metres is often measured against significant time barriers. For men, the 10-second barrier is a major barometer of elite performance. Jim Hines was the first man to break this barrier with automatic timing at the 1968 Olympics. Usain Bolt of Jamaica holds the current men's world record with a time of 9.58 seconds. He set this record in Berlin, Germany, on 16 August 2009. For women, the standard for elite sprinters is finishing in eleven seconds or less. Florence Griffith-Joyner of the United States holds the women's world record at 10.49 seconds, set in 1988.

Environmental factors play a critical role in the recorded times of these athletes. Air resistance can significantly impact how fast a runner moves. A strong head wind is detrimental to performance, while a tail wind can improve it. For a record to be considered "wind legal," the tail wind must not exceed 2.0 metres per second. Additionally, athletes often perform better at high altitudes. The thinner air at high altitudes provides less resistance against the body. While breathing may be slightly more difficult due to lower oxygen pressure, this effect is negligible for such a short distance. Performances at altitudes greater than 1000 metres are marked with an "A" to denote the condition.