Impress your friends

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  Triathlon originated in the United States as an alternative training programme to keep track and field athletes fit

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  The first official triathlon took place in San Diego, USA, on 25 September 1974 and consisted of a 500m swim, 8km cycle and 10km run

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  On its Olympic debut at the Sydney 2000 Games, half a million people lined the streets to watch the races

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  At Athens 2004, Austria’s Kate Allen was 44th out of 50 in the swim and 28th after the cycling, but fought back in the run, taking the lead with 200m left to claim the gold

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  New Zealanders Hamish Carter and Bevan Docherty won gold and silver in Athens, achieving the first and so far only triathlon one-two in Olympic history

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  A photo finish was needed to confirm that Nicola Spirig had won gold at London 2012, after the Swiss crossed the line in the same time as Sweden's Lisa Norden

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  Australia is the most successful nation in Olympic triathlon, with five medals – one gold, two silver and two bronze

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  Canada’s Simon Whitfield is the only triathlete to win two Olympic medals – gold at Sydney 2000 and silver at Beijing 2008

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  Great Britain's Alistair Brownlee won gold at London 2012 in the fastest time recorded at an Olympic Games, while his brother Jonathan won the bronze

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  Triathlon is one of the few sports with no heats

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  Only once in the eight Olympic competitions held has the difference between first and second been greater than 13 seconds

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  Triathletes can be warned or disqualified if they threaten the safety of their rivals during any of the three sections

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  Non-Olympic 'Ironman' triathlons consist of a 3.8km swim, 180km cycle and 42km run, while 'Ultraman' competitors swim 10km, cycle 421km and run 84km