Medley swimming is a combination of four different swimming styles, including backstroke, breaststroke, butterfly, and freestyle, into one race. This race can be swum by one swimmer as an individual medley (IM) or by four swimmers as a medley relay. In individual medley, a single swimmer swims equal distances of four different strokes within one race. The strokes are swum in the following order: butterfly, backstroke, breaststroke, and freestyle. In medley relay, four different swimmers each swim one of the four strokes, with the stroke order being backstroke, breaststroke, butterfly, and freestyle. The reason for this order is that backstroke is started from the water, and if it were not the first event, the starting backstroke swimmer and the finishing previous swimmer could block each other. The remaining strokes are sorted according to speed, with breaststroke being the slowest and freestyle being the fastest stroke.