marathon----don't quit your day job. I am not suggesting that spirometry isIt seems that the straining should be in your core not your head. Try to isolate the forcing to your mid section, that is where the residual air is, not up in your head.
going to induce an ANEURYSM----however the effects of forced expiration on
the PHYSIOLOGY of DA WHOLE DAMNED BODY----cannot be wished away with
silly words like "DO IT FROM YOUR CORE"