Start lying on your back with your legs in tabletop position (hips and knees at right angles). Engage your deep abs to round your lower spine into the floor. Make sure you are not "pooching" your abs, which means you are just working the top layer of abs, which is a Pilates no-no.
Exhale and lift your upper back off the floor, until the bottom tips of your shoulder blades skim the floor. Straighten your legs to a 45-degree angle (but make sure your low back is staying connected to the floor). Reach your arms toward your feet. Your arms will be about two inches off the floor.
Pump your arms up and down with a small range of motion, keeping your elbows straight. Inhale for five arm pumps, and exhale for five pumps. That completes one set or cycle. Repeat the cycle nine more times for a total of 100 pumps.