How the Olympic triathlon works

HOW TRIATHLON WORKS AT THE RIO OLYMPICS

* The men's and women's races will feature 55 starters apiece

* The venue is Fort Copacabana

* The race starts with a 1.5km ocean swim, followed by a 40km road cycle and a 10km run - although distances can vary

* "T1", the swim-bike transition, and the bike-run "T2" are critical parts of the race where valuable time is won and lost

* There are strict rules governing transition, such as when triathletes can put on and take off their helmets, and the time penalties involved can be decisive. A potential nightmare scenario for the sport is if a time penalty affects the medal placings

* Drafting on the bike, or pack riding, is often illegal in triathlon - but it is a fundamental part of the Olympic format

* The first three competitors across the finish line win the medals.