Healthy lungs are capable of providing all that room and more.
The lungs are filled with millions of tiny air sacs, which transport oxygen into the blood for vital tasks such as producing energy. Spread out flat, the air sacs would cover an area almost the size of a tennis court. None of us comes close to using all of our lung capacity. This capability is called vital capacity. Lack of activity also decreases the heart's ability to pump blood back to the lungs, which also affects its function.