In layman's terms, different breathing patterns can serve as a quick and often easy way to manipulate your emotional and physiological state in ways that allow you to be calmer, less stressed, and more productive.
Our lungs are filled with receptors that tell our brains whether we are inhaling or exhaling, explained Dr. Patricia Gerbarg, an assistant clinical professor in psychiatry at New York Medical College and co-author of The Healing Power of the Breath. As we inhale, we activate the sympathetic state (the fight-or-flight system). As we exhale, we activate the parasympathetic state (the calm and collected system). This is why yoga-style breathing exercises often involve long exhalations.