Backstroke is the only standard competitive swimming stroke in which swimmers are face-up in the water. Unlike freestyle, breaststroke and butterfly, the swimmer begins on the back and keeps the face generally above the surface while moving down the lane.
The stroke uses alternating arm movements: one arm recovers over the water while the other pulls beneath it. A flutter kick supplies much of the continuous propulsion. Because swimmers cannot look directly toward the finish wall, they use lane markings, overhead flags and the number of strokes they typically take to judge when to turn.
Backstroke is also unusual in competition because races begin in the water rather than from starting blocks. The modern competitive version developed from the back crawl, and its technique is governed by World Aquatics rules. Swimmers may roll their shoulders and body during the stroke, but they must remain on their backs except during the permitted turning action.