Deeper and longer inhales increase heart rate, while longer and more intense exhales slow heart rate and promote calmness.

“If you wanna calm down, you can do that quickly by making your exhales slightly longer than your inhales or making them more vigorous.”

“So if you want to speed up your heart rate and be more alert, inhale more or make those inhales more vigorous, more intense.”

“This is what we call an increased vagal tone. So let me explain for a moment. And actually here's a tool you can use, not just in terms of navigating grief, but in terms of stress modulation, generally. We have a muscle called the diaphragm. When we inhale, [inhales] whether or not it's through our mouth or our nose, our diaphragm moves down. As a consequence, there is more space overall in the thoracic cavity. The heart gets a little bit bigger, believe it or not, volume-wise, blood flows more slowly through that large volume. And there's a signal conveyed from the nervous system to the heart to speed the heart up. So inhales literally speed your heart up. And when you exhale, the diaphragm moves up. And as a consequence, there's less space in the thoracic”