If you're looking to work the abdomen portion of your core, you don't have to plop down on the floor of your office to fit in a stomach workout. (Who knows what lingers down there anyway?) Instead, look no further than your own desk chair.
Here's how it works. Sit down nice and tall in your chair -- make it a sturdy one without wheels, if possible. Push your shoulders back as if you are trying to appear as "professional" as possible. Move to your chair's edge and place your hands on the sides of the chair or on the armrests.
You are now in position. While keeping your back straight, lift your knees. Bring them up to your chest and then back down. You can let your legs go all the way to the floor during the exercise, or not allow them to touch the ground between reps to make it even more challenging. According to Erin Kurdyla for Self.com, one option is to try two sets of 12 [source: Gallo].