- We hear a lot nowadays about heart rate variability. For those of you that have heard of it, and for those of you that haven't, having a higher HRV or heart rate variability is a good thing, right? Normally, if you hear something like heart rate variability, sounds like a bad thing, turns out it's a great thing.

Heart rate variability is essentially the distance or the time rather between beats of the heart. So you might think that it's great to have a really consistent heart rate, boom, doom, or actually in reality, it's more like and I'm missing some of the beats within the wave form, but you get the idea.

But actually it's well known to be correlated with a number of positive health outcomes, including things related to brain and body and longevity and performance to have high heart rate variability. Heart rate variability is going to lead to a pattern of heartbeats that is more like Now, you might say that's arrhythmia.

Ah, but there are cases of arrhythmia that are good and there are cases of arrhythmia that are bad. Higher HRV in general is a good thing. You want it during sleep and you want it during wakeful states. In sleep, heart rate variability comes about because this vagal pathway from nucleus ambiguous, the cell bodies, the nuclei, literally the DNA within those nuclei of those neurons reside in nucleus ambiguous and they project to the sinoatrial node.

And every once in a while, they'll just pump the break on heart rate and slow heart rate down. And then they'll come off that break, slow down, come off heart rate. And here's the really beautiful part. And the way that you get actionable leverage over the system, The control by the vagus nerve of the sinoatrial node and heart rate is coordinated with your breathing.

Now, as I tell you this, it'll make perfect sense, but I just want you to step back from it a second and realize that these systems of the body are so elegantly coordinated. And here's how it works with respect to heart rate and breathing. When you inhale air, of course, your lungs expand.

You have a muscle that sits below your lungs called the diaphragm. As you inhale air, of course, that diaphragm moves down. Now, as your diaphragm moves down and your lungs expand, your heart literally has a bit more space in the thoracic cavity to expand. Okay, it's not going to swell massively, but it's going to expand.

Now, as a consequence of that expansion, the blood that's moving through your heart is going to move a little bit more slowly per unit volume. That is sensed by a particular group of neurons in your heart. And that sends a signal to your sympathetic nervous system to speed your heart rate up.

Put differently, inhaling speeds your heart rate up. Now, the converse is also true. When you exhale, your lungs deflate, your diaphragm moves up. And as a consequence, there's slightly less space for the heart. So the heart shrinks a little bit, not a ton, but it shrinks a little bit.

And it's enough such that whatever blood is in the heart moves through more quickly per unit volume. That faster movement is sensed by neurons within the heart, sends a signal to the brain, and the brain activates those neurons within nucleus ambiguous, and very quickly sends a signal to the sinoatrial node to slow your heart rate down.

Put differently, exhale, slow your heart rate down. And they do so by way of vagal control over the sinoatrial node. This is the deceleration pathway over heart rate. So as I mentioned, this is happening all the time during sleep. You don't have to be consciously aware for this to happen.

It's a fortunate consequence of nature that the neurons within your brainstem that control breathing, and the neurons within your brainstem that control heart rate, and the other neurons within the heart itself that control heart rate, the pacemaker cells, all can function without you having to think about it. That's a wonderful thing for obvious reasons.

It's also the case that because we have this input from the left dorsolateral prefrontal cortex down through a couple of other structures, like the cingulate and the insula, and that converge on nucleus ambiguous, if you decide to slow your heart rate down, you can do it. And you do so by doing a deliberate exhale and or by increasing the intensity or the duration of your exhale.

So you can do that right now. If you want to slow your heart rate down, that is if you want to increase parasympathetic nervous system activity, and you want to calm down fast, you can literally just . Exhale, slow your heart rate down, and exhales tilt that seesaw that is the autonomic nervous system more toward the parasympathetic side.

Now, I've talked before on this podcast and all over social media about the so-called physiological sigh, a naturally occurring form of breathing that occurs in sleep and that we can deliberately do anytime we want to calm down fast. And the physiological sigh consists of, as many of you know, two inhales through the nose, followed by a long to lungs empty exhale through the mouth.

Typically the first inhale is longer. Again, it's done through the nose. The second inhale is shorter, kind of a sharp inhale to make sure you maximally inflate all the little sacks within your lungs. And then the exhale is a long, slow exhale that dumps all your air. I'll just demonstrate the physiological sigh for you.

For those of you that haven't seen it, you again, big inhale through the nose, second sharp inhale through the nose to make sure you maximally inflate the lungs, and then long exhale to lungs empty. It goes like this. Okay, lungs are empty. That is indeed the fastest way to activate the parasympathetic nervous system, and to tilt that seesaw from levels of high sympathetic nervous system activation to lower levels of sympathetic nervous system activation.

In fact, I immediately feel calmer. Maybe you can even hear it in my voice. So when you do a physiological effect, you're getting both a chemical signal into the brain. That is the adjustment of that carbon dioxide oxygen ratio. It's mainly due to the offloading of carbon dioxide. That lower level of carbon dioxide is registered by the brain very quickly and leads to an increase in calm.

The deceleration of heart rate driven by the exhale is also registered by the brain very quickly, leads to an increase in calm. When you just emphasize an exhale, meaning you extend it or you make it more intense, and you don't do the two inhales first, that is you don't do the physiological sigh.

Well, you get the mechanical signal, but you don't get the chemical signal, at least not to the same degree you do with the physiological sigh. Put simply, if you want to calm down fast, ideally you do the physiological sigh. However, it turns out that one of the best ways to improve your HRV, both in sleep and in wakeful states, which takes a very minimum of effort and is rarely if ever discussed, is simply throughout the day, I would say 10, 15, maybe even 20 times per day, anytime it occurs to you to just deliberately extend your exhale, that is to pump the brake on your heart rate through the vagus nerve pathway that I've been describing.

Just, just exhale, slow your heart rate down and then get about your normal routine. You can do that essentially anytime you remember to. This is literally going to increase your HRV. You now know the mechanism by which it does that. And get this, it will also increase your HRV in sleep at night.

And the reason is this pathway that originates with the left dorsolateral prefrontal cortex and goes down to nucleus ambiguous and then to the sinoatrial node of the heart because it's under conscious control and because it's subject to what we call plasticity, to strengthening and to weakening. That is, if you use it deliberately, it gets strengthened.

If you don't use it deliberately, it gets weakened. Well, that's a great thing because it means that if you just simply remember to do some extended exhales throughout the day, you're going to strengthen this pathway such that it operates in the background through auto-regulation without you ever having to think about it.

Now, of course, that effect wears off over time if you don't occasionally remember to just do some, some longer exhales. But this is a wonderful protocol in my opinion, because it capitalizes on a inborn circuit, right? A circuit that you were born with that is already installed, that you can use at any point.

It doesn't take any learning, but that if you just ping every once in a while with some extended exhales throughout the day, it takes essentially no time. You get the benefit of feeling a little bit calmer, slowing your heart rate down and your HRV, which is correlated with a host of positive health outcomes in the short and long-term will increase.

you get the benefit of feeling a little bit. You get the benefit of feeling a little bit. It's a good thing. You get the benefit of feeling a little bit. You get the benefit of feeling a little bit. You get the benefit of feeling a little bit.