Each of the four athletes in the team must run with a baton in his hand, passing it on to the next athlete in the team until the final athlete crosses the finishing line. The baton is a smooth hollow tube, 28-30cm long and about 4cm wide. Each athlete runs one 100m leg of the track.
The changeover is the crucial point in the Relay race. The key is for both athletes to be running at speed while passing the baton within the defined zone.
The competition start with heats. The number of heats and the number of teams who progress to the next round depends on the number of teams competing. In each heat the best-placed teams go through, as well as a set number of the fastest losing teams across all the heats. The following rounds run on the same format, until eight teams qualify for the final.
The draw to determine which heat teams run in is decided by their initial seedings (based on previous performance) for the first round, and then their performances after that. This ensures that the highest seeded teams are not drawn in the same heat.
Keys to success
A good start for the first athlete is vital. The winning teams also pass the baton in the most efficient manner – with both athletes maintaining as near to top speed as possible.
An athlete who starts running too early risks having to slow down again or run out of the changeover zone, and an athlete who leaves it too late loses momentum.
Breaking the rules
Although it is not against the rules to drop the baton, crucial time is lost picking it up, and if in doing so one team obstructs another team, they are disqualified. The baton must also be passed within the designated zone.
Find out more about the Men's 4x100m Relay competition at the Olympic Games on the International Olympic Committee website.