When resting, your lungs breathe in and out up to 25 times per minute. Their basic task is to bring in oxygen to the body via air and exhale carbon dioxide -- a substance your body can't use. However, when you exercise your lungs are put under greater strain to perform this task. You may feel like you have to breathe deeper and faster to keep up with your body's demands.
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Your lungs are made from a spongy material that expands when you breathe in air. They're protected by your ribcage and supported at the bottom by a layer of muscle called the diaphragm. Inside the lungs, tiny sacs called alveoli sit at the end of a network of very thin tubes. The alveoli allow the transfer of oxygen from the air to the blood. This transfer is basically the same whether you're resting or exercising.
Exercise means the muscles in your body need more oxygen to work. To provide the extra oxygen, your brain tells your diaphragm and rib muscles to work harder. As your diaphragm flattens out, it enlarges your chest cavity. Because of the relative pressure change, air rushes into your lungs. Your lungs then expand to fill your enlarged chest cavity. When your lungs reach near their maximum volume when exercising, your diaphragm tightens once again and forces the air out.
Your pulmonary vessels transfer blood to and from the lungs. When you exercise, your pulmonary vessels increase their blood volume up to four times. The overall volume of blood in the lungs rises by around 10 percent, allowing for the absorption of more oxygen for the heart to pump around the body via red blood cells.
A professional athlete training at his highest rate can increase his breaths per minute to around 40 to 60, according to the British Lung Foundation. That equates to 100 to 150 liters of air filling the lungs and emptying again every minute. This is why lung capacity and the ability to control breathing when exercising can help improve athletic performance.