Amount of air taken in per minute Amount of air inspired per minute = breaths per minute X amount of air per breath (mL/breath) (mL/min) Sample problem: At rest: Breathing rate = 12 breaths per min. Volume of air per breath = 500 mL/breath Intense exercise: Breathing rate = 30 breaths per min. Volume of air per breath = 2000 mL/breath 1. How much air is Susie breathing per minute? At rest: Intense exercise: 2. Why does Susie's body need so much more air during intense exercise? 3. Exercise activate the nervous system and this a) sympathetic; increase b) sympathetic, decrease c) parasympathetic; increase breathing and heart rate. d) parasympathetic; decrease