I don't know if this is something idiosyncratic or just something that everyone deals with, but I have a difficult time breathing when my diaphragm is compressed, such as when I'm crouching (which makes things a good bit more difficult for Capoeira) or when I'm bent over as in a pike stretch or doing the yoga plough position. I get a lesser effect when in a deep lunge. I think that what's happening is that, in those situations, my legs are pressing into my diaphragm, compromising how well it can work, but the best I can manage is shallow breathing, not exactly conducive to remaining long in the position, particularly since I have a hard time shaking the idea that I'm just not getting enough oxygen.
Are there any tricks to improving this other than just continuing to do these exercises and hoping that my body catches on that it needs to adapt? I'm in reasonable shape for someone in a sedentary position. I can climb several flights of stairs at a brisk pace without losing my breath and I have not tested positive for exercise-induced asthma.