The main purpose of these exercises is to activate the autonomous nervous system. In addition, it’s a great way to gauge the degree to which the breathing exercises have attenuated the speed at which your body acidifies. The autonomous nervous system is composed of two branches: the sympathetic (fight-or-flight) and the parasympathetic (rest-and-digest) nervous system. Doing push-ups with your lungs full of air activates the SNS, whereas doing them after exhaling activates the PSNS.