Exercise and the Lungs The amount of air you need to breathe in depends on how active you are. When you are sitting down you only take in about 15 breaths a minute, giving you around 12 litres of air (a litre is one and three-quarter pints). From this your lungs will extract just one fifth of a litre of oxygen.
During exercise your breathing and heart rate increase. Exercising flat out, a top-class athlete can expect to increase his/her breathing rate to around 40 to 60 breaths a minute. This means they take in an incredible 100 to 150 litres of air, extracting around five litres of oxygen every single minute. Even those of us with more modest goals need to double our lung intake when we exercise. Our lungs must be able to respond to our body's increased demands for oxygen.
What happens when you exercise? As you start to move about, the muscles in your body send messages to your brain that they need more oxygen. Your brain then sends signals to the muscles that control breathing - your diaphragm and the muscles between your ribs - so that they shorten and relax more often. This causes you to take more breaths. More oxygen will be absorbed from your lungs and carried to the muscles you are using to exercise - mainly your arms and legs.
Why do muscles need more oxygen? For you to become more active your muscles will need to produce more energy. They do this by breaking down glucose from your food, but to do this they need oxygen. If there is too little oxygen they will try to produce energy in a different way. But this can lead to a build-up of a chemical called lactic acid, which causes cramp - something that many athletes are all too familiar with.
Athletes train so that their lungs and muscles become more efficient and it takes longer for lactic acid to build up. This means that their muscles can work harder. In fact, everyone can benefit from exercise to strengthen their lungs and muscles. Through exercise you can train your body so that more oxygen is delivered to your muscles.