Sit on top of your balance board, feet flat on the floor, knees bent, legs together, arms crossed at your chest, abs engaged, and back as straight as possible.
INHALE: While maintaining a perfectly flat back, hinge from the hips to lean backward, only leaning as far back as you can while still maintaining a straight spine. EXHALE: Use the abdominals to lean forward to the start position, sitting upright to complete one rep.
Try to keep your legs together and your feet on the floor at all times. Lengthen through your back (spine), and engage your abs (pull your belly button toward your spine) at all times. Keep your shoulders relaxed.
Make it harder: Instead of crossing your arms at your chest, extend them up next to your ears.
Muscles Worked: Abs