Anytime you're seated is an opportunity to strengthen your core. Instead of slouching and relaxing into a "C" shape, imagine there's a thin coat of paint covering the back of your chair. In order to steer clear of the paint, think about positioning yourself on top of your sit bones—this is your foundation. From there, stack your vertebrae on top of your foundation, keeping the natural "S" curve of your spine as you pull your belly button in toward your spine. Try this: Inhale, then slowly exhale all the air out of your lungs. As you exhale, hold in your abdominals. Repeat 3 to 5 times.