You're about to give a presentation. Or you're stressing over your company's cash flow. Or you're worrying about the future and unable to sleep. Wouldn't it be nice if you could release a chemical into your bloodstream whenever you wanted that would immediately relax you and help you focus calmly on the task at hand?

You can, it turns out. In a fascinating blog post on the Psychology Today website, endurance athlete and coach Christopher Bergland details the science that explains how a simple breathing technique can bring calm and mental clarity. The technique is simply to make your exhalations longer than your inhalations. The best way to do this is by counting--inhale to a count of four and exhale to a count of six, for example--which is how it's often taught in yoga classes. As you gradually feel more calm you can extend those counts, for instance inhaling to a count of six and exhaling to a count of eight. But even the simple act of counting as you breathe, slowing your breath in general and exhaling to a longer count than you inhale will make you calmer and better able to concentrate.

Bergland is a champion endurance athlete who has three times won the Triple Ironman (bike 336 miles, swim 7.2 miles, run 78.6 miles) and set a Guinness World Record for running 153.76 miles in 24 hours on a treadmill. He says he learned the breathing technique from his father, a neuroscientist and tennis player, who would use it before beginning complex surgeries or important tennis matches. 

Slowing your own heartbeat.

Why does this technique work so well? Because of the vagus nerve, the longest nerve in your body, running from your brain stem all the way down to your colon. The vagus nerve monitors the state of your organs and feeds information to the central nervous system. And it helps regulate your heartbeat.

As experiments have shown, while you inhale, your heartbeat speeds up slightly. Then while you exhale, the vagus nerve releases a neurotransmitter substance called acetylcholine or ACh which goes directly to the heart, telling it to slow down. Having your heart rate slow is a very calming thing, but even more important, inhaling slowly and then exhaling more slowly increases your heart rate variability, according to Bergland. And, he writes, greater heart rate variability is associated with "lower chronic stress levels, better overall health, and improved cognition."

Calming your body and mind with longer exhalations is part of the benefit behind the popular practice of 4-7-8 breathing, which is known to reduce stress levels, improve overall health, and help people fall asleep.

So next time you're feeling tense, or you're faced with a challenging task, try 4-7-8 breathing or simply try inhaling to a count of four and exhaling to a count of six. I can't promise that it will make everything go smoothly, or take all your jitters away. But I can guarantee that you'll feel more focused and calm than you did before.