Lots of garbage has been written about breathing. In voice, if it’s complicated, not only is it wrong, but it will fall apart when you least expect it to. (This is my definition of “technique.”) The whole point is the coordination between the breath flowing out and the vibration in the vocal folds. This is energy flow, and that doesn’t require force or effort.
Natural posture opens the body up and allows the breath to seem to come from all the way down and go all the way up. That’s all that needs to happen in breathing.
Foreman, Edward V. Voice Without Technique: A Manual for Singers and Speakers. Pro Musica Press, 1998.