Feel bad about not making it to the gym? This fun move will have you sweating up a storm. Begin sitting, balanced just behind your sits bones, and rock back slightly to lift your feet off the floor; gently pull your knees to your chest. Exhale, pull your navel to your spine, and lean back slightly as you open your arms to the sides and straighten your legs. Inhale and return to the starting position to complete one rep. Do 20 reps.