Dr. Wu told us the ab roll-up works all four abdominal muscles at once, while "assisting with segmental mobility and stability of the core."
Lie on your back with arms overhead.
Bring the arms forward until they are above your head (fingertips pointing to the ceiling).
Lift the head and together with the arms roll your spine up one vertebra at a time, keeping your navel pulled into your spine.
Roll up completely until you are bending forward reaching toward your toes.
To return, stack your vertebra one at a time, until you are sitting erect, and then slowly roll down starting from the sacrum (pelvic tilt backward to touch sacrum down first) one vertebra at a time until you are lying flat on your back again with arms overhead.