Swimming

First Olympic Appearance: 1896 (men); 1912 (women)

by John Gettings and Mark Zurlo

In the first modern games any stroke was allowed, but today four swimming strokes are used at the Olympics. The backstroke first appeared in 1900, breaststroke in 1908, butterfly in 1956, and the freestyle, which can be any technique, has been almost exclusively a technique called the Australian crawl since the 1960s.

Men and women will compete separately in 17 events. The only difference is the men swim a 1500m freestyle race and the women swim a 800m freestyle race.

The backstroke, breaststroke and butterfly races are held over 100m and 200m. Freestyle races are held over 50m, 100m, 200m, and 400m, as well as the 800m for women and the 1500m for men.

Here is what happens in the medley races:

Individual (200m, 400m): Each competitor uses a different stroke on each lap of the race in this order: butterfly, backstroke, breaststroke, and freestyle.

Relay (4x100, 4x200): A different swimmer swims each leg of the race using a particular stroke in this order: backstroke, breaststroke, butterfly, and freestyle.

At the London Games, 950 competitors will be swimming in 34 events between July 28 and Aug. 4. The majority will be vying for medals in the Aquatics Centre, a state-of-the-art permanent structure boasting a 50m competition pool, a 50m warm-up pool, seating for 17,500, and a wave-inspired roof that is 160m long and up to 80m wide. For those competing in the Marathon Swimming 10km, they will swimming 6 circuits of a course marked out in Hyde Park's Serpentine Lake, a man-made lake constructed in 1730.