The little red man is what I look like after 50 contractions!
I don't know where to read about contractions, but I will describe the process as best as I can. Try it at home. If you hold your breath long enough, there should be a point where you have an involuntary contraction of your diaphragm. If you don't get one the first breath hold, then breathe up again and hold again. You probably will have to hold for a while, way past the urge to breathe to feel since you are an adept breath holder already.
They are your body trying to force as much O2 as possible from your lungs into your bloodstream, and to mix the air around in your lungs so as to access the O2. It works, and can be a good training and preparation aid. They can also be used as an indicator to return to the surface. I will comfortably accept 10 contractions on the way to the surface during shallow rec diving, more for constant ballast attempts, and as many as 50 during a static attempt.
Give it a shot, but of course be careful amigo
, maybe tell your wife what your doing so that she doesn't walk in and think that you are possessed!
Cheers,
Erik Y.
