Slouching in front of your computer for hours on end doesn't do anything for your core, so give this challenging move a try. If your chair is on wheels — bonus — it'll be even harder to hold your body still. Just be sure to lift and lower your body slowly to prevent rolling.
Place your hands on the base of the chair. If your chair has arms, for an easier version, place your hands on each arm. Press into your palms, keep your knees bent, and lift your tush off the seat. Lift your knees as high as you can to get the most out of this ab exercise. Hover over your chair for a few seconds, or longer if you can. Then slowly release your buns back to the chair. Repeat two to four more times.