You can find this exercise on page 209 of the book Synergistic Golf.
Exercise Type: PILATES
Exercise Category: ABDOMINALS, BALANCE, STRENGTH
Lying down, flex feet and feel the lengthening of your legs away from you. Reach arms to sky, but focus on trying to flatten belly button to spine and spine to floor. Lift head and inhale. As you exhale, reach arms toward feet and roll up keeping spine flexed (rounded) and ribs tucked in toward hips. Reach toward feet, then roll back down slowly with control never allowing a stretch between ribcage.