"The physiological sigh is the fastest hardwired way for us to eliminate a stressful response in our body quickly in real time," says Andrew Huberman, an associate professor of neurobiology at Stanford University School of Medicine.

"The physiological sigh is something that we do spontaneously, but when you're feeling stressed, you can do a double inhale, followed by a long exhale." He demonstrates how to do this in the video. He breathes in deeply through his nostrils to fill his lungs, then does another quick inhale through his nose. Then, he exhales slowly through his mouth.

He explains how this is effective in reducing the stress response:

"Your lungs aren't just two big bags, they contain millions of little sacs throughout. These sacs actually make the surface area of your lungs as big as a tennis court. These sacs tend to collapse when we get stressed. So, when you do the double inhale, exhale, the double inhale reinflates those little sacs in the lungs. And then when you do the long exhale, that long exhale is much more effective at ridding your body and bloodstream of carbon dioxide, which relaxes you very quickly."