The lungs are strengthened by regular exercise. Your lungs are, in effect, twin balloons that have a porous lining to absorb the oxygen you need for energy. The more they can inflate, the more oxygen they can absorb. When you are inactive for long periods, you tend to breathe in a shallow way, inflating your lungs only enough to stay alive. This can leave you feeling tired and listless much of the time and make you vulnerable to chest infection.

Regular physical activity improves the elasticity of lungs, which allows them to inflate with greater ease.

During exercise your lung capacity increases five to seven times. Some of this increased capacity stays with you when you are not exercising, so you breathe deeper to produce more power for the muscle and fuel for the brain.