Filling the lungs
The amplitude of breathing
We can consciously control how much air we take into our lungs and how much air we expel from our lungs. This is our amplitude of breathing.
When we fully inflate the lungs by pulling the lungs from the bottom, sides and top, our lungs are filled at full capacity. The full capacity of our lungs is about 6 liters.
When we deflate the lungs, there is still some air left in the lungs, so actually when we inhale, we suck in about 4,8 liters of fresh air.
Generally, when we breathe, it is a good practice, not to inflate the lungs to maximum capacity. We should expand the stomach to max and expand the rib-cage to max. When we get to the chest, we should expand it close to max but not max. We should avoid forcefully emptying the lungs to the minimum but rather leave a little bit of air. A full inflate or a minimum deflate, may trigger a stress reaction and is better to avoid, in normal breathing.
When exercising, we can use our lungs fully. Inflating to the fullest, when we inhale (maximum) and emptying the lungs as much as we can, on the exhale (minimum). This way the lungs remain elastic and we are exercising our breathing muscles.