Four strokes are used in Paralympic competition: Freestyle (essentially front crawl), Backstroke, Breaststroke and Butterfly. All four strokes feature in the Medley Relay and 200m Individual Medley events; in addition, all of them except Butterfly feature in the 150m Individual Medley events for certain classifications. Races take place in a 50m pool, and may be started in a number of ways: from a standing start; using a dive start from a sitting position on the starting platform; and from within the water.
Swimmers are classified according to how their impairment affects their ability to perform each stroke. Classification numbers 1-10 cover athletes with physical impairments, with class 1 swimmers’ impairment having the greatest impact on their ability to perform strokes, through to class 10 swimmers’ impairment having the least impact. Athletes with a visual impairment compete in classes 11-13, with class 11 having little or no sight, through to class 13 having limited sight. Athletes with an intellectual impairment compete in class 14.
Breaststroke uses greater leg propulsion than any other stroke, therefore athletes with a physical impairment often have a different class for this event compared to Freestyle, Backstroke and Butterfly. This is also taken into account when athletes compete in the Individual Medley. This is shown by the prefix:
S before the class represents Freestyle, Backstroke and Butterfly events.
SB before the class represents Breaststroke events.
SM before the class represents Individual Medley events.