Emotional stress, chronic holding in of the abdomen and poor breathing habits can blur the "contractile maps" and relaxation maps of the diaphragm resulting in chest breathing with the scalenes,serratus posterior inferior, quadratus lumborum, and the intercostals becoming overburdened. Within the fitness industry there are many iterations of tensioning and inhibiting maximum diaphragm descension displacing intraabdominal pressure downward on pelvic floor and/or upward possibly contributing to GERD and thoracic cavity disfunction, Uddiyana bandha, and many other fitness cues invite pulling in the abdomen, "engaging" the core, drawing the belly to the spine, tucking the tail and drawing in navel. Add to this the pervasive cultural ideal of a flat tummy and these alone may be a recipe for diaphragm disfunction. Any clothing that constricts the abdomen is also certainly an issue.

belly down crocodile breathe with blocks

banded breathing

diaphragm "reset"

https://www.youtube.com/watch?v=kacMYexDgHg&t=290s

5 min animation on lungs/respiration

Carbon dioxide is the waste product of the respiritory system, and of several other chemical reactions in the body, such as the creation of ATP. Pure carbon cannot be transported in the body, so CO2 is one form it takes that is water soluble. Levels of CO2 also tell the body when it needs more oxygen. Carbon dioxide has 3 very important functions

1 It is a dilator of smooth muscle. Smooth muscle surrounds any hollow space in the body, ie. bronchial airways, bladder, bowel, arteries etc. If your alveolar CO2 level is low the smooth muscle around these hollow spaces will spasm and constrict

2 Transport of oxygen to the tissues. Oxygen is transported to the tissues through the bloodstream via the haemoglobin molecule, each haemoglobin molecule carries 4 oxygen molecules bound to it, the Bohr effect proves that if the alveolar CO2 levels are too low, the oxygen molecules will not dissociate from the haemoglobin molecules to the optimal level

3 It is the regulator of PH levels of the blood