Computer-generated image of the human skeletal muscles involved in a kick. The leg works like a powerful three-part lever. Muscle groups working with and against each other swing the thigh at the hip, pivot the lower leg at the knee, and tilt the foot at the ankle. The calf muscle pulls on the heel bone to tilt the foot down while the opposing muscle in the shin pulls on the front of the ankle and foot bones to raise the toes, multiplying the force and accuracy of the kick.