Diaphragmatic breathing is, in many ways, the ideal way to breathe in that it's the most efficient way to breathe ... If you want to know whether or not you're using diaphragmatic breathing, it's very simple ... If you inhale, and your belly moves outward on the inhale, well, then that phrenic nerve is controlling your diaphragm properly. And then when you exhale, your belly should go in just a little bit.