Sit up straight on a high stool.
Ensure you find pelvic neutral with your weight directly through your seat bones and not your tail bone.
Look directly ahead and tighten your abdominal muscles.
With your arms relaxed to the side, lean your body backward.
Keep your feet on the floor.
Ensure you keep your gaze forwards and slightly up, and your shoulders relaxed.
You should feel the effort in your tummy muscles.
Control the movement as you return to the upright position, and then repeat.