The Science of Deep Breathing: Simplified

“Just breathe” is a phrase we hear all the time, especially when we seem visibly stressed. The certainty with which it is directed at us tells us that something about breathing is supposed to help us feel calm and relaxed. And help it does- we know that deep breathing can lead people to feel less anxiety, self-doubt, and nervousness, while also helping them to feel more focused (Paul, Elam, and Verhulst, 2007). People report feeling better, but does it really have any effect inside the body? To answer that, we need to revisit our high school biology class (where's Ms. Frizzle when you need her?).

The beneficial effects of "deep breathing" have to do with the relationship between our “rest and digest” system (aka the parasympathetic nervous system) and our “fight or flight” system (AKA our sympathetic nervous system). These two systems work in sweet harmony and will function without any conscious effort on our part. That said, both deep breathers and self-critical thinkers around the globe have realized that they can in fact activate one system over the other with a bit of extra work.

both deep breathers and self-critical thinkers around the globe have realized that they can in fact activate one system over the other with a bit of extra work.

Keep in mind that while a threat used to be a bear in the woods, modern day threats can include anything from being stuck in traffic, to a job interview, to self-criticism, to the fear of failure. Unfortunately, our stress response is not so good at differentiating between a real or a perceived threat, so it will activate regardless of the type of stressor. That’s why even things like intense and prolonged self-criticism can create a stress response in the body. When we are stressed, our “fight or flight” system activates. Our heart beats faster and our pulse quickens. Blood vessels leading to our heart and large muscles dilate, allowing more blood through so that you can essentially fight or escape whatever threat is causing that stress. If stress stays for a while, our body can become flooded with stress hormones like cortisol that can lead to cardiovascular health issues.

When we relax or rest, it’s finally time for our “rest and digest” system to shine. This system slows down that racing heart, it decreases blood pressure and fixes any dry mouths, and energy is redirected to digestion. Simplified, it has the opposite effect on our body than our fight or flight system, so it helps our bodies maintain balance. Within our rest and digest system is something called the vagus nerve. The vagus nerve is a cranial nerve complex that is connected to many glands and organs (Berthoud and Neuhuber, 2000). Basically, the vagus nerve is a superstar of our rest and digest system because of its involvement in so many functions. Here’s the really neat thing about the vagus nerve: It’s actually modulated by respiration, which means that when we exhale it activates, and when we inhale it is suppressed (Gerritsen and Guido, 2018). Following that connection, we see that deep breathing works to calm us because it increases our vagal activity and decreases the activity of our fight or flight system. That’s why studies looking at the effectiveness of deep breathing also find that it can lower heart rate and cortisol stress levels (Perciavalle et al., 2016) and lower blood pressure levels (Mori et al., 2005). To jump start our vagus nerve, then, we want to make sure we are exhaling longer so that it has time to work its magic on our rest and digest system.

we see that deep breathing works to calm us because it increases our vagal activity and decreases the activity of our fight or flight system.

So, is there any difference when it comes to breathing exercises?

There are all sorts of breathing exercises that are taught; common exercises you might have heard of include 4-7-8 or finger breathing. It doesn’t really matter which technique you prefer. We know from the research that, regardless of the technique, what’s important is that:

• The exhale is longer than the inhale (that’s going to activate your vagus nerve. Remember that it is the celebrity of our rest and digest system and “comes to life” during exhale)
  

• The breath is a deep one, meaning it comes from the diaphragm and not the chest (you can practice by putting a hand on your stomach while you breathe; you should feel it extending outward. If you’re breathing deeply and exhaling longer, chances are you’re doing diaphragmatic/belly breathing anyway)

My favourite breathing exercise involves finding what breathing rhythm fits best for your body and lung capacity. I’ll count the seconds starting from 1 and ask the other person to flag me down when they feel just full enough of air but not too full. Then I’ll count the seconds of their exhale. The goal is to make sure that they can extend the exhale for at least two seconds past their inhale, ensuring it is longer. It’s quite common for young adults to have an inhale of 4 seconds and an exhale of 6-7 seconds. If they can’t make it to that exhale mark, then we change the inhale to 3 seconds and the exhale to 5 seconds. The takeaway: Deep breathing does change what’s going on inside of our bodies by activating our vagus nerve, which is part of the system that will turn off our stress response. The longer you breathe and the more frequently you practice, the more likely you are to notice a calming effect.

The takeaway: Deep breathing does change what’s going on inside of our bodies by activating our vagus nerve, which is part of the system that will turn off our stress response. The longer you breathe and the more frequently you practice, the more likely you are to notice a calming effect.