The 4 × 100 metres relay or sprint relay is an athletics track event run in lanes over one lap of the track with four runners completing 100 metres each. The first runners must begin in the same stagger as for the individual 400 m race. Each runner carries a relay baton. Before 2018, the baton had to be passed within a 20 m changeover box, preceded by a 10-metre acceleration zone. With a rule change effective November 1, 2017, that zone was modified to include the acceleration zone as part of the passing zone, making the entire zone 30 metres in length. The outgoing runner cannot touch the baton until it has entered the zone, and the incoming runner cannot touch it after it has left the zone. The zone is usually marked in yellow, frequently using lines, triangles or chevrons. While the rule book specifies the exact positioning of the marks, the colours and style are only "recommended". While most legacy tracks will still have the older markings, the rule change still uses existing marks. Not all governing body jurisdictions have adopted the rule change.
The finish at the Rio 2016 Olympics
Sprinting is running over a short distance at the top-most speed of the body in a limited period of time. It is used in many sports that incorporate running, typically as a way of quickly reaching a target or goal, or avoiding or catching an opponent. Human physiology dictates that a runner's near-top speed cannot be maintained for more than 30–35 seconds due to the depletion of phosphocreatine stores in muscles, and perhaps secondarily to excessive metabolic acidosis as a result of anaerobic glycolysis.
Usain Bolt, world record holder in 100 m and 200 m sprints
This sprinter's initial crouch in the blocks allowed her to preload her muscles and channel the force generated from this into her first strides.
The stadion of ancient Nemea, Greece.
Start of the women's 60 m at the 2010 World Indoor Championships