Understanding the anatomy of good breathing is an essential step in mastering it,. As we inhale, the diaphragm should contract downward, displacing the abdominal contents and resulting in a slight swelling of the abdomen. The External Intercostal muscles contract to expand the upper ribcage. On the exhale, the diaphragm relaxes back up into the ribcage, while the Internal Intercostals contract to gently close the ribcage.
Some individuals demonstrate Paradoxical Breathing, where the abdomen sucks in when they inhale, rather than the other way around. This often takes some focused work to correct, but is time well spent, as everything starts to improve when the breathing is more functional.