Perform this exercise on a flat, semiresilient surface. It is a basic drill for developing power throughout the entire torso and applies to many sports. The primary emphasis is to attain maximum height and vertical reach with every effort.
Assume a relaxed, upright stance with feet about shoulder-width apart. Slghtly flex the arms and hold them close to the body.
Begin by flexing downward to a half-squat position; immediately check this downward movement and explode from this takeoff position upward as high as possible, extending the whole body vertically. As the body descends, flex the joint so the body is again poised in takeoff position upon landing. Repeat this flexion to full height extension with minimal movement away from the vertical plane.