OK, I've started using the tables, and while on a smoke break I got to wondering just what I'm training myself to do. I know what the end result is (being able to hold my breath longer), but exactly what am I changing? Am I conditioning myself to use less oxygen or to withstand more CO2? Am I gradually reseting that trigger in my brain that says "breathe or you will die"? What is the physical and or mental process going on here that allows me to breath hold for increasingly longer periods of time?