Wab Board + Lumbar
Wab Board: Sit on the bench with the back of your knees against the edge of the shorter end. Put your feet under the foot bar and lie down. Make sure your lower back is entirely glued to the bench. Use your abs to lift your upper body. Keep your neck straight, look towards the sky. For comfort you can put your palms on your neck, but do not pull it. Go back to the initial position.
Lumbar: Place your feet on the foot bar, your pelvis against the crossbar. Lean your upper body forward to descend
Strengthening of the abdominal and back muscles.