Love Your Stretch Receptors
By Kristine Kaoverii Weber | August 11, 2023
Breathing is really complicated – one of those topics where the more I study it, the bigger it seems to get. Today I want to share just a little something about a critical part of the breathing mechanisms that I hope will be helpful for you in understanding why pranayama + breath-centric asana practice are so freakin’ spectacular!
Please say hello to your stretch receptors.
Stretch receptors are sensory receptors in your lungs that are sensitive to volume and pressure changes. When you breathe in, these little guys get activated and send electrical signals to your medulla, a part of the brain stem.
One of the reasons they do this is so the medulla can tell your lungs to stop inhaling.
This essentially prevents your lungs from overinflating like balloons. (For anyone who wants to geek out a little on the science, the mechanism that prevents this is called the “Hering-Breuer Reflex.”)
Another thing the medulla does is, at the end of your inhale during the slight (or intentionally longer) pause, it send signals via the vagus nerve to the Sinoatrial node, which is basically the heart’s pacemaker, telling it to slow the heck down.
So, just to make this clear. When you breathe in deeply, during the pause at the end of the inhale, your brain tells your lungs to stop filling up, and signals your heart to start to slow down.
I realize that may sound counterintuitive.
We often think in yoga that the inhalation is activating and exhaling is relaxing, and that’s accurate, but it’s not the whole story.
Think of it this way: the breath is constantly cycling your autonomic nervous system – in a way similar to how yin and yang are constantly spiraling with, emerging from, and then collapsing back each other.
Stretch receptors are also involved in prompting inhalation. When you exhale, the lungs relax and the stretch receptors are no longer activated. This in turn tells your medulla that you need to breathe in, so it fires up the inhalation process again.
The stretch receptors can help us understand why using pranayama practices that accentuate the (short) pause at the top of the inhale is so helpful for kicking in the relaxation response. You’ve just enjoyed a full inhale, you briefly pause your breath at the top, the medulla is like, okay, that’s enough, stop breathing in, meanwhile it’s signaling the heart to slow down, and then, when it was just about to get fed up with you, you go ahead and release this nice, long, slow exhale. Your heart slows even more and tunes the systems towards a more parasympathetic (rest and digest) mode.
Short retentions after the inhale are actually really good for relaxation. The key word here is “short” – longer retentions can have the opposite effect. And please keep in mind that everyone’s nervous system is a little different so what works well for one person may not be appropriate for another.
Here’s a short pranayama practice to try to play with your stretch receptors kicking in the parasympathetic response:
- Start with 4 counts in and 4 counts out – do that 3-4 times.
- Try 4 in, 2 pause, 4 out – 2 times.
- 4 in, 2 pause, 6 out – 2 times.
- 4 in, 2 pause, 8 out – 6 times.
- Return to 4 in, 2 pause, 4 out – 2 times.
- 4 in, 4 out – 2 times.
Then pause and notice how you feel.
Let me know what you think!