The 100-meter sprint is all about speed. Any wasted movement or misstep will almost certainly lose you an event that is often decided by tenths of a second. The rules for the 100-meter are simple and straightforward, but infractions are met with immediate disqualification.
Start
All athletes in the 100-meter sprint start with their feet in the angled starting blocks and their weight balanced on their fingertips before the starting line. Starting blocks cannot overlap the starting line or touch another runner's lane. They need to be fixed to the track with pins, rigid in construction and can't give any unfair advantage to the athlete. When the official fires the competition gun, it signals the beginning for the athletes to push off the blocks and race across the finish line. A false start will be met with immediate disqualification from the event.
Track Measurements
The distance of the race is measured from the edge of the start line farther from the finish to the edge of the finish line nearer to the start. Each runner's lane is exactly 1.22 meters wide and there should be eight lanes. In terms of the slant, measurements are taken extremely seriously. The lateral inclination of the track should not exceed 1:100 and the inclination of the running direction should not exceed 1:1000 downwards.
Disqualifications
Any runner who obstructs another runner's lane or view during the race may be disqualified at the referee's discretion. The athlete affected by the obstruction may earn another chance to compete in another heat of the race. If any athlete gains an unfair advantage by crossing outside of her own lane, they will be disqualified, but if she doesn't gain an advantage, she will be allowed to continue.
Finishing the Race
Since 100-meter sprint athletes are so fast, it's often impossible for the naked eye to tell who won a race. Photographic evidence is used to separate the winner from the rest of the pack. Whichever athlete gets his torso over the finish line first is declared the winner. Your arms, head, neck and legs don't count in a photo finish. Although hand timing can be used, the International Association of Athletics Federations says automatic photo timing devices should be used in all races and must be approved by the IAAF. Additionally, a transponder system may be used where the athletes wear automatic timing devices on their uniforms. In the rare case of a tie, both athletes may be permitted to continue in a later round of the race. If it isn't practical, the athlete originally ruled the winner will remain so.
References
Writer Bio
Steven Kelliher is an experienced sports writer, technical writer, proofreader and editor based out of the Greater Boston Area. His main area of expertise is in combat sports, as he is a lifelong competitor and active voice in the industry. His interviews with some of the sport's biggest names have appeared on large industry sites such as ESPN.com, as well as his own personal blog.