This is a great Pilates-style core exercise.
Sit on the mat in a v-sit postion, with your knees bent at approximately 90 degrees. Your hands should be in the pockets of the Pilates band and the band should be around your feet.
Inhale and pull your navel to your spine. Slowly let yourself roll backwards, keeping your navel pulled in and your back rounded. Use your momentum to bring yourself back to the starting position. Balance for 2-3 seconds, then repeat the roll. Repeat 8-12 times.