RIO DE JANEIRO - Everything about the Olympic triathlon at Rio in five facts:
Leeds-based duo, Alistair (L) and Jonathan Brownlee, who often work together in races, are hot favourites for Rio honours
+ Triathlon, first officially staged in California in 1974, was only added to the Olympic roster at Sydney in 2000. A bit like climbing Everest, triathlon represents a supreme test of physical endurance. First up is a 1500m freestyle swim in freshwater. Then still dripping water competitors hop on their bikes for a 40 kilometre ride, with the third leg a 10 kilometre run - time taken to change clothes is included in the overall result. In Rio, 55 men and 55 women will be taking part, with no more than three athletes per country.
+ The physical pain that awaits competitors will be partly offset by the splendour of the 2016 triathlon venue, at Rio's iconic Copacabana beach, with the cycle section eight 5km laps around the hills of dos Cabritos and do Cantalgo, concluding with four 2.5km laps by the shoreline.
+ Amazingly, given the distance and multi-discipline nature of triathlon, only centimetres split gold and silver in 2012, with Switzerland's Nicola Spirig claiming the women's title on the nod from Swede Lisa Norden. Norden tried to get the result overturned by the awarding of a joint gold after they clocked identical times but her appeal was rejected by the Court of Arbitration for Sport. Hot favourite to succeed Spirig in Rio is the American Gwen Jorgensen, beaten only once since 2014.
+ Spain's five-time men's world champion and London silver medallist Javier Gomez, winner of the Olympic trial event in Copacabana last year, is cruelly ruled out after breaking his arm in a freak cycling accident.
+ Gomez's absence leaves the stage clear for the Battle of the Brownlee brothers, the remarkable British siblings Alistair and Jonny who grew up fell-running and cycling in their hilly home county of Yorkshire. Alistair struck gold in London, with Jonny, two years younger, claiming bronze. The arduous demands of the discipline on the body were readily exposed when after crossing the line 31sec behind his brother, Jonny collapsed requiring medical treatment. Alistair retained family bragging rights at the 2014 Commonwealth Games leading a Brownlee 1-2 in Glasgow. The Leeds-based duo who often work together in races, are hot favourites for Rio honours. Among those out to stop them are France's Vincent Luis and Spaniards Mario Mola and Fernando Alarza.