Flutter kick

In swimming strokes such as the front crawl or backstroke, the primary purpose of the flutter kick in beginner and intermediate swimmers is not propulsion but keeping the legs up and in the shadow for the upper body and assisting body rotation for arm strokes.

The knees are slightly bent to facilitate the kicking action, but not too much in order to minimize drag created by the thighs as they move out of the shadow of the swimmer's body.

The downward moving leg provides a majority of the thrust by creating vortices which swimmers use to increase velocity.

[4] The calisthenics version of the flutter kick is often used as an intensive training tool in the military.

Starting position is lying flat on the back with the feet and head approximately 6 inches (15 cm) off the ground.