Flutter kick

The flutter kick is a kicking movement used in both swimming and calisthenics.

In swimming (either front crawl or backstroke), the legs are extended straight out in line with the body and then moved up and down, the one leg kicking downwards as the other leg moves up again. The legs are separated to not enhance wingtip vortices. The toes point in the direction of motion to mimic a hydrofoil. The knees are slightly bent to adjust the angle of attack.

The calisthenics version of the flutter kick is often used as an intensive tool in the military. They help to develop the hip-flexors, abdominal muscles, and legs. Flutter kicks are a four-count exercise. Starting position is lying flat on the back with the feet and head approximately 6 inches off the ground. Hands are under the buttocks; fists are clenched to support the lower back. Count one; raise the left leg to a 45-degree angle, keeping the right leg stationary. Count two; raise the right leg off the ground to a 45-degree angle while, at the same time, moving the left leg to the starting position. Counts three and four are repetitions of the same movements. Legs must be locked, with toes pointing away from the body.