physiology behind static apnea
interesting subject you guys are discussing:
the phisiology of it is like this:
first you take a deep breath, once you hold it, the venous return to your heart increases (this means your heart is taking up more blood) and this causes your heart rate to go faster initially because of the negative intrathoracic pressure. after a while, your heart regulates itself and begins to decrease its rate and there are several reasons for that
1. vagal stimuli (reflex that slows your heart beat) which is stimulated by the cold water, by your breathholding effort and by the hypoxia ( as the time runs)
it´s called the mammalian reflex: is really a vagal response. after doing specific trainning you can develop more rapid response, like stepanek, your vagus kicks in and you go into bradycardia quicker
Exercise 1: try doing static apneas with full exhalation and you will notice how your heart beat will drop up to 30 bpm in no time! (don´t forget to have a buddy with you as these tecniques can be dangerous, for you are doing them in very hypoxic conditions)
Exercise 2: measure your heart beat breathing normally, then take a full inhalation and measure it again. what happens: your heart beat goes up 10-12 bpm. then measure your heart beat after a full exhalation. it goes down again. this is called respiratory arrhytmia and is a physiologic phenomenon explained by the changes in intrathoracic pressure and how it affects the venous return and cardiac output.