Lie on your back, arms resting on your belly, knees bent, feet flat on the floor. Breathe normally a few times. Don't flatten your back or tilt your pelvis, but try to maintain the natural curve of your lower back. Breathe slowly and deeply.
Take a deep breath and tighten your abdominal muscles as you exhale, pulling your navel toward your spine. Concentrate on contracting the muscles below the belly button without flattening the back.
When you are able to contract and relax your abdominal muscles without arching or flattening the back, you are isolating the correct muscles (and can safely move onto Sahrmann Exercise #1).