1. Lie on your stomach on top of a physioball. Make sure that your torso is flat and your upper body/arms are straight (plank position).
2. Elevate the right leg while keeping the knee from bending, leading with your heel. Keep your hips pressed into the ball to prevent rotation.
3. Return to start position and switch sides.
4. Repeat for prescribed number of repetitions.
Be sure to: Keep arms and legs straight. Do not lift legs above parallel to the ground.