Triathlon is the youngest of all Olympic sports. It was invented by San Diego Track Club as an alternative workout, with the first known events held in 1974. The club's first triathlon comprised of a 10 kilometre run, 8km cycle and 500 metre swim.

Athletes must excel at three different pursuits - swimming, cycling and running - to master the triathlon, which is considered the ultimate endurance test. All three events are done one right after another, with no breaks in between.

In 1994, at the International Olympic Committee's Congress in Paris, France, triathlon was awarded full medal status in the Olympic and triathlon made its debut at the 2000 Games in the shadow of the iconic Sydney Opera House. The first winners were Switzerland's Brigitte McMahon and Canada's Simon Whitfield.

Technical

The Olympic triathlon comprises a 1.5 kilometre swim, 40km bike ride, and 10km run. Men will typically complete the course in around one hour 50 minutes, with women taking a little over two hours.

A mass start can lead to jostling for position during the swimming. Thereafter, the race is continuous and, as there are no stops between the three legs, changeovers from one discipline to the next are crucial to race strategy. Positions can change rapidly throughout the race, as athletes make up places during their stronger disciplines and fall back during weaker ones.

The men's and women's races both have 55 entrants selected from qualifying events held in the run-up to the Olympics.

Major player

Six gold medals have been contested in the Olympics so far and a different country has won on each occasion. The most successful nations have been Australia and New Zealand, who have won four and three medals each respectively. The most successful individual athlete has been Canada's Simon Whitfield, who won the first men's race in the shadow of the Sydney Opera House in 2000 and then eight years later in Beijing won the silver.

Bluffer's guide

Athletes are not allowed to receive assistance from anyone else inside or outside the race, with the exception of race-sanctioned aid volunteers who distribute food and water on the course. This also means that team tactics, such as drafting, a cycling tactic in which several riders cluster closely to reduce the air resistance of the group, are usually not allowed.

Useless information

Tim Don, Britain's 2006 world champion, is the son of Phil Don, a former Premiership referee.