Working out your chest probably isn’t the first thing on your to-do list in the gym—but maybe it should be. Your chest muscles (a.k.a., pectoral muscles or "pecs," which are some of the largest in your body), are responsible for your upper body's stability, helping you to maintain proper posture, and even play a part in your ability to breathe deeply. Plus, they help you tackle everyday functional tasks like pushing open doors or picking up groceries.

Over the next 21 days, expect to tone those chest muscles, increase flexibility, and possibly even give your breasts a lift (breast tissue sits on top of the pectoral muscles, FYI) with these 17 strengthening and stretching moves. Get started and put your best chest forward.