Grab a pair of dumbbells and sit with your knees bent, feet flat on the floor (knees and ankles touching). Pull your abdominals in tight, round your back, and slowly lower to the floor until just your head and shoulders are off the ground. Bring both arms to the outside of your hips, hovering parallel to the floor, palms facing up. Slowly and with control, round your back and roll up through your spine, lifting elbows in line with your shoulders and curling the dumbbells into your chest as you sit up.
At the top, lift your chest and straighten your spine as much as you can, bracing your abs in tight, arms bent at 90 degrees. That's one rep. Repeat 20 times total.