HOW: Begin by lying on your back with knees bent, feet flat on the floor. Take the knees of both legs towards the chest and the hands of both arms towards the feet. Using a Swissball, connect the hands and the knees for a static hold. Using both hands and the ball as resistance, continue to press the knee of one leg into the ball. With the other leg, slowly lower the heel to tap the floor. Return to knee to chest position.
FEEL: You should feel your front and side abdominals. You should feel the front of both hips.
COMPENSATION: Avoid letting the shins sag down towards the floor. Avoid arching your low back.