#305 ‒ Heart rate variability: how to measure, interpret, and utilize HRV for training and health optimization | Joel Jamieson

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My guest this week is Joel Jameson. j is the CEO and founder of Morpheus Labs and Eight Weeks Out.
Morpheus Labs aims to work with trainers and individuals to maximize training results using a combination of data science and physiology, primarily through heart rate and heart rate recovery training systems. The system is used by a number of professional sports teams in the NFL, NBA, MLS, NCAA, and more.
Eight Weeks Out is a company that helps coaches, athletes, and fitness enthusiasts improve their strength, conditioning, and performance. In this episode, we speak about what sparked Joel's personal interest in the world of heart rate variability and the history of heart rate variability development over time.
We break down the science of HRV and how HRV is calculated. There are many different methods and how the interplay between the sympathetic and parasympathetic nervous system affects your heart, the reliability of tracking HRV, and ultimately what it is that HRV is telling us about these autonomic nervous systems.
We talk about the decline of HRV with age and what drives this change and how much of it is within our control versus genetically predetermined. We then talk about Morpheus, which is a product that ultimately led to my meeting Joel.
We talk about my skepticism around Morpheus when I first began to use it and ultimately why I came to believe that it is a really valuable tool for people when they're training, especially people who might not be as interested in, for example, using lactate testing or other really advanced forms of testing to fine-tune their training zones. We talk about the impact of lifestyle choices on HRV and its significance for overall health and how to use the data from HRV to inform daily choices.
Finally, we talk about HRV within the broader context of other health metrics and where it sits in the hierarchy of measurable insights. Final point I'd like to make is that while we speak extensively about Morpheus, I want to make sure everybody understands I have no financial affiliation whatsoever with Morpheus.
I'm not an investor in the company. I'm not an advisor to the company.
We have no affiliate deal with Morpheus. Of course, we have no affiliate deal with any company.
In other words, there is no financial remuneration of any sort that exists between me and this company. I am simply a huge fan of this company, and I speak about it often, recommend it to a number of my patients because of my belief in its efficacy in helping people achieve their exercise goals.
We do discuss a couple of other companies in this podcast that I do have relationships with. These have been disclosed previously, and they're all on my disclosure page, but I would like to again reiterate them here.
I am currently a scientific advisor to the company AteSleep, and I am a passive investor in the company Aura. Those two companies do have a mention in this podcast as well.
So without further delay, please enjoy my conversation with Joel Jameson. Hey, Joel, thanks for coming out to Austin.
Been looking forward to this discussion for some time. We've not met before, but had what seems like an endless stream of email communication.
So I always appreciate your willingness to not just respond to all my questions, but the thoroughness with which you do so. This is a topic that, as we were discussing just a few minutes ago, I think everybody has heard of it.
People have a vague sense of what it is, but once you get beyond a very superficial description of it, most people, I think, don't really understand it. And certainly most people don't understand how to use the data.
And I would absolutely include myself in that category. So the topic, of course, of heart rate variability is near and dear to your heart.
Maybe before we dive into the weeds of this stuff, maybe just give folks a bit of a sense of your background and what brought you to the study of this and over what period of time? It's really interesting to me to see the growth of it because I've been using it now for 20 years. And the story of it's really fascinating to me because I was in my early twenties and I had just graduated from University of Washington, interned there and done some strength conditioning and then was progressing to the Seahawks to work with the same coaches.
And there was a track coach named Randy Huntington. And most people probably never heard of Randy, but he was the USA track and field jumps coach.
He coached Mike Powell, who broke Carl Luce's long jump world record. In 1993, right? Something like that.
Yeah. So Randy was around for a long time.
He was a tremendous coach and he was from my area. And I just kind of was talking to him one day and I asked him some general advice, you know, as a young coach, what would you suggest and resources and all sorts of stuff.
And he writes a phone number down for me and says, you need to call this guy. And I was kind of like, okay, you know, whatever you say, Randy.
And so I call this guy and this thick Russian accent answers the phone and says, his name is Val. And I still don't really know what I'm calling this guy for.
I just know that Randy told me to. And so he says, I'll be in your area.
I'll meet you at the airport. I still, I'm like, okay.
I'm just kind of playing along and I'm not really sure what the whole point of this is. But Randy says, call this guy.
So I call this guy and he just says, I will show you the technology. And I'm again, kind of like, okay.
So I go down to the SeaTac airport and I see this kind of big Russian looking guy with a trench coat. I mean, it looks like it could be straight out of a movie.
Introduce himself. And he's like, lay down on the couch.
I hope you're now out of the airport or? No, I'm in the hotel by the airport. And so again, I'm just in the dark of what is going on.
And he says, lay down on the couch. And so I lay down on the couch and he's like, take your shirt off.
This point I'm looking around like, is there some kind of practical joke? Like, is Randy just messing with you? This is when you have a lot of faith in Randy. He doesn't have a lot of faith in Randy and paid off.
And so he does this big briefcase and he pulls out this big laptop and he starts plugging in wires and all this sort of stuff. And he pulls out these electrodes.
He starts putting them on my chest. And he does basically an ECG, asking me birth date and weight and all this sort of stuff.
And he's like, don't move. And so I sit there for two and a half, three minutes.
And I see all this stuff on the computer happening. And again, still just completely in the dark.
What is this guy doing to me? Like, I have no idea. I mean, after about three minutes, he's like finished.
And he starts kind of telling me about my recovery status and my readiness my metabolic profile my central nervous system starts talking about all this stuff that didn't really make a whole lot of sense of how you would know and he was like you're much more strength oriented and your cardiovascular system is not very good which is accurate at the time maybe didn't take a computer to see that because I was definitely on the strength side but he started just telling me the story of HRV and heart rate variability. And this was, again, 20 plus years ago.
It was not something that people were aware of and I had never, of course, heard of it. And the idea that you could take something out of a laptop, connect it to my body and have any idea of physiologically what I was as an athlete or as a human being was completely new and seemed foreign to me and immediately was like, I need this.
Because it seemed to me like there's so much of a black box when it comes to fitness. Sometimes I do a workout and I get better.
Sometimes I do workouts and I don't. Why? What is the right magic answer here to always get the workouts that I want to see are the results? And so he started talking about the story of heart rate variability.
And this is really fascinating because you don't read this when you look at the Western literature.

So you probably know it goes back way, 1700s.

They're aware of B2B intervals.

Chinese have used pulse medicine a long time.

But the Russians were pretty ahead of the game as far as application of HRV.

So in the late 1950s, they were aware that from an ECG, you could pull out these B2B intervals and get something more than just heart rate. And so when they would send the first human being in space, Yuri Gagarin, they were able to send back the ECG and some respiratory data and see fundamentally what happened to people when you shot them into space, which they really didn't have a way of gauging without this.
And so they saw as soon as he went into space, his HRV went way up, probably because you have changes in blood pressure, you have less gravity, so you don't have to have as much muscle activity. And they started using this literally all the way back in the 1960s, which is pretty fascinating because you didn't really see that in the Western literature for decades later, really in a meaningful way.
Then in the 1980s, they were dominant as far as all the Olympic sports, right? They just crushed us. Now they had a very elaborate drug program.
They had a very elaborate training program. They had a lot of different things that gave them the advantage.
But in the mid 1980s, they started basically figuring out, can we use this tech for sport performance? And so they put together an engineering team and they started collecting data on thousands of Russian athletes of all levels from their school age kids all the way up to the Olympic athletes. And they collected just populational norms and they started building a system that was meant to monitor training and be used for this purpose.
Don't get me wrong, they had really high volumes, but they did blood monitoring like weekly or monthly. They were constantly testing.
They, from an organizational standpoint, their communist structure gave them a very hierarchical way to organize this sort of stuff and monitor it. So anyway, they spent years working on this platform.
And then before they could finish it, the Soviet Union collapsed and kind of the whole team that was involved in this just dispersed and left Russia. And just by chance, a lot of them had been involved in track and field, different sports.
They ended up reconvening in a track meeting Eugene and kind of just talking about this past project. And they decided that they want to get together and keep working on this because they'd never brought it to fruition.
And they did. And that was ultimately the first system that I think was available.
I mean, it was the first system that was available commercially with the intent of being used for sport and fitness. And that was what I was being introduced to at the time.
This was the result of this project being finished. The problem is they wanted $35,000 for it.
It was a very research heavy medical type system that was not easy to interpret. I didn't have $35,000, but I convinced them to let me help them introduce it to teams across the US and gain some exposure for them as we worked at a deal and I started using it.
But it gave you 12 or 14 different metrics of heart rate variability. It required you, like I said, connect electrodes to people before you'd measure them.
And really it was that introduction to it where I started this whole journey and 20 years of looking at data and coaching people and trying to understand what the data was telling me and how it aligned with all these other metrics has really just led me down this path of how you get to our rate variable today. And it's certainly been a large change, but it's kind of that crazy journey of starting one day in a laptop in a hotel next to the airport.
And now it's on everyone's phones and watches and everything else. But I spent 20 years coaching with it and that's really the difference is I was a coach, I opened a gym, I worked with lots of fighters and athletes and different teams and military groups using data, looking at HRV, the whole nine yards.
So it's been a long time, but it's really fascinating to see it grow. So let's talk a little bit about the actual measurement.
So in the example you gave when you were first introduced to it, it was done off an EKG. I assume three leads would be sufficient.
It was six back then. Okay.
But you can certainly get it from three, obviously. Yeah.
So would we say, Joel, that that's still the gold standard for how to measure HRV? Absolutely. I mean, if you're talking about medical grade research quality, you want the cleanest signals, you want the most signals, ECG, three lead, six lead is by far the way to go.
This might be a little too in the weeds, but given how technical this topic is, do you want to explain how an EKG works? Because I think it will be relevant to distinguish between what an EKG is doing, what a chest strap is doing, what an optical sensor is doing on the forearm, on the wrist, or on the finger. These are all going to be basically the tools the technology companies are using to measure HRV.
But as you and I have discussed and gone deep on this, there's a total difference in the fidelity of the signal depending on where the signal is acquired. And given that our audience here is an appreciative audience for nuance, I think it might be worth explaining from the gold standard all the way down, how these signals are acquired, what's happening physiologically and electrochemically that's enabling the capture of the signal.
Sure. I mean, you can kind of group these into two things, right? One is the electrical signal of the heart itself.
And that's what we're measuring with an ECG or EKG or the chest strap. You're literally measuring the polarization, repolarization of the heart as the chambers are beating.
And you get this electrical signal that gives you the QRS complex. And we're honing in on where those beat-to-beat intervals are.
Because ultimately, to get HRV, we need the exact amount of time from one heartbeat to the next, because that's what we're quantifying. So if you have an electrical signal, you get a very clear, clean signal that you can pull out those exact beat-to-beat intervals.
And that's where we fundamentally get heart rate variability from. Is it always done R to R because that's the cleanest signal? Yeah, it's always done R to R.
So you just have to be able to identify where is the peak of the R interval. The more accurately you can identify, here's the peak of the R wave, here's the peak of the R wave, the more accurately you can get that.
And if my memory serves me correctly, because it's been so long, right? So the P is the polarization of the atria. And then the QRS is the ventricular, is it the repolarization or the contraction? I believe it's the contraction.
Yeah. And then the T wave is the repolarization.
Exactly. So you're basically, the R wave is giving you, if my memory serves me correctly, I'm sure there's a cardiologist listening who's going to scream right now, but that's the peak electrical signal of the contraction of the ventricle.
Exactly. Yeah.
I'm not a cardiologist either, but from my memory, that's correct as well. But yeah, you're getting this exact electrical signal that's showing us where that peak is happening.
And because it's at high resolution and it's electrical, we can pick that out pretty easily, especially the more leads you have, the more you're going to be able to get that. The difference between that and an optical sensor.
And tell me, by the way, if I'm wearing a polar chest strap, which is what I wear when I'm on my bike, I have a chest strap. How is the fidelity of that compared to an EKG? It's pretty close, honestly.
It's very close. As far as picking out the actual peak of the R-wave, it's going to be within a millisecond, which is more than enough.
Now, obviously, if you have a full six-lead EKG, you're going to get even more, but you don't need it for HRV as long as you can identify that peak of the R-wave precisely within one or two milliseconds of what it's actually at. And that's where the gold standard is, is from the ECG.
And just to give folks a sense of that, a millisecond, a thousandth of a second is the unit that HRV is typically being measured in. So if a person is looking at their HRV and they're seeing a number that says 60 milliseconds, you're saying with a chest strap, you would put a plus or minus of one or two milliseconds on any reading that comes out? As long as it's a good chest strap.
Now, the caveat is good skin contact and those sorts of things. If it's moving around or it's not in the right place, you can lose some of that, which of course you have a better chance of getting the signal correct with actual electrodes.
That is really the gold standard, and that's how it was done for decades. That's how most 90 plus percent of the research has been done with either the EKG or with chest straps because that's really been the gold standard of how it's measured.
The use of these PPG or optical sensors really has only been the last five, six years they've been around and traditionally their accuracy was just questionable when it came to it. And they don't get the same electrical signal.
They're measuring changes in blood volume through the skin. Basically, the electrodes shine the LED light down into the skin.
It reflects differently based on the blood flow flowing through the arteries below it. And so you're getting the pulse and they actually call it pulse rate variable.
It's not really heart rate variability. If we want to get technical, it's pulse rate variability, but it's showing us the same thing.
It's showing us that cardiac cycle. Now there seems to be a big difference between the wrist and the forearm.
So on my bike, if I'm riding indoors, well, actually I'm doubling up. So I'm wearing, people are going to be like, what is wrong with this Peter guy? He has so many stupid devices.
It'll all come to full circle through this. When I'm on my bike indoors, if I'm outdoors, I'm just wearing my polar chest strap because it pairs perfectly with the system, with the bike system I'm using outdoors.
Indoors, I ride with my Morpheus chest strap and my Wahoo optical sensor. The reason is I'm using two different programs.
The Wahoo sensor on my forearm, which is optical, is pairing with my computer and that program I'm using there in erg mode. But the reason I'm using the Morpheus chest strap is I'm using the Morpheus program on my phone.
But the reason I bring all that up, Joel, is to say they're perfectly in sync. The chest strap, the gold standard, and the optical sensor on my arm, never off by more than a beat.
And I can see them in real time concurrently. Conversely, when I'm rucking, when I'm putzing around, I wear a Garmin GPS watch that measures heart rate.
It's a very high-end watch. It's about a $700 watch.
It is categorically a piece of garbage. I would call it a random number generator for heart rate.
It can't come close to estimating my heart rate. There are times I look down and it says I'm at 170 beats per minute when I know I'm below 100.
Conversely, there are times when I'm probably at 160 beats per minute and it says I'm at 110. So as far as I can tell, it serves absolutely no purpose.
Occasionally it's accurate, I'm sure, but it's so inaccurate so often that I would never rely on it. I'm using it for GPS.
I'm almost annoyed that it's a feature that is there. They're both optical sensors.
Why the difference? Yeah, one is location, as you mentioned. To get a good resolution, you need good blood flow below the surface, and you need the lack of movement.
The biggest problem with PPG sensors, optical sensors as a whole, is they get what are called motion artifacts. And any kind of movement starts introducing noise into the signal.
Because again, we're not getting electrical signal. We're just getting this blood flow going beneath the surface that we're using the LEDs to detect for heart rate.
When you start moving around, you get lots and lots of motion artifacts, and it just becomes much more difficult for those sensors to detect it accurately, particularly in like acyclical movements, anything where your arm is moving around at random, higher heart rates, darker skin colors, lots of things throw off PPG sensors. So my darker skin is obviously a disadvantage, presumably.
Just in general, tattoos, all of these things. So optical sensors in particular struggle with higher intensities, higher movements, higher heart rates, all those sorts of things.

Now, my optical sensor on the bike, even though admittedly I'm not really moving, my upper body isn't obviously moving, is it superior because it's less movement or is it superior because it's on much larger blood vessels? Both, right? So there's a company called Valencell that we use.

It's done a lot of research on this because they produce the sensors and they've looked

at any location, bicep, arm, calf, all of the above.

Even your wrist, you have bone movement. Even if you're not really moving, your wrist can still be flexing and extending.
And just that wrist movement will cause motionary effects. You get much cleaner blood flow on the forearm.
You get just much less movement and torsion as you're moving. So you get just a much better overall signal on the forearm in general than you're going to get from the wrist.
They've looked at accuracies of garments and whoops, and you don't get very good accurate data at all, as you've seen when you're doing exercise. And even when you're doing somewhat cyclical exercise, you can still get, as you've seen, completely garbage numbers that make no sense because the sensor just can't pick up the blood flow very accurately.
And like I said, tattoos, dark skin makes it far worse. So in general, the desk trap is always going to be the gold standard.
But if you're going to wear an optical sensor, the forearm where you can get good blood flow is going to be by far the best place to be able to put it. And you can even manipulate where in the forearm you tend to get the best signal, the best results.
Yeah. I don't know if I'm doing it correctly, Joel.
I tend to apply it right beneath the antecubital fossa where I know the artery is running. That's what you want.
And I'm sort of like assuming that I'm going to get the best signal there. And I also put it on pretty snug.
I mean, I was just doing that, not thinking about motion artifact, but it sounds like that you would encourage that. You want a good enough skin contact that can read.
You don't want to smash it in there. I'm not using it as a katsu band.
Yeah, exactly. Not doing BFR with my...
You should get a forearm pump and you probably have it a little too tight. So it's almost like there's really three.
I know you said there's two buckets. You could really say it's anything on the chest, amazing gold standard.
Always going to be good as long as... Anything on the forearm.
I think we've established if you do the forearm right, at least heart rate to heart rate is comparable. We'll talk about the HRV variability.
And then anything below the forearm is sort of nonsense. It's not great.
It's definitely not great, especially if you're lifting weights, if you're doing interval training, if you're doing anything high intensity, you're doing change of direction. It's garbage.
You just get very poor data and I wouldn't rely on it. It might be accurate sometimes, and sometimes it'll be way off.
The one that seems to be, I wouldn't say accurate, but the most accurate, the less accurate is the Apple Watch. And I think what they're doing, since they can actually have ECG, I think they're just interpolating a bunch of data.
So when they see bad data, they just kind of replace it with what they think the data actually should be. I see.
So you're saying the Apple Watch might be a step ahead of other wrist-based devices based on sampling an algorithm. You can detect when the junk data is there, you don't have to display it.
The other ones do. But they have enough previous data to know your heart rate didn't go from 110 to 160 in two seconds.
So I think they'd start building the algorithm out to interpolate that. Yeah, it's odd that Garmin tolerates that, for lack of a better word, because I'll see it do that, right? I'll see it go from 100 to 150, and I'm like, that's not even physiologically possible.
Why wouldn't you sample that out or ask a second-order question? Yeah, great point.

Okay, let's now talk about the very confusing subject of how one calculates heart rate variability.

Because let's again reiterate what we're talking about. So if anybody has seen an EKG, everybody watching us has, you've got your little PQRST and you just line up a strip of those.
And you imagine you were doing this in the olden days, you'd have a set of calipers, you'd literally measure across R to R to R to R. So let's pretend we have a minute's worth of data, Joel, and a person's heart rate is they're laying down and resting.
So they're at 60 beats per minute. So the approximate beat to beat interval is one second.
On average, sure. Yeah, on average, or 1,000 milliseconds.
What's happening at the physiologic level that makes it such that there is variation? And how is that measured and calculated from the raw data? And let's start with the gold standard and assume you have an EKG. Yeah, as you mentioned, you're starting with this gold standard of, okay, we can accurately

pinpoint where are these R to R intervals. And so we pull out what are called the R to R intervals,

surprisingly, and we'll plot those. Now, from there, you do what's called correction, basically.

You have to filter data there for filter ectopic beats, which are beats that don't actually arise

in a single atrial node. You fill out if there is any noise in the signal or anything like that,

and you end up with this clean set of R to R intervals. So let's say I gave you 60 of them.
And it's, again, it's a person who's at rest. So on average, it's a thousand milliseconds between them, but I'm going to give you 60 numbers that vary from 900 to 1100 milliseconds.
So this is where things get interesting because when we talk about HRV, we just usually give a number and that number can be different. But a better way to think about HRV is just a framework to assess variability because there are multiple ways to calculate that.
There's one category called time domain where we literally just do some math. The most common one is RMSSD, root mean successive squared differences, where they just do some basic math and they get that number of milliseconds of RMSSD.
There's SDNN, there's PNN50, there's all these different, call them time domain, where they just are taking that time series, doing some math on it, and giving you a number that represents the average variability. So let's talk about the RMSSD, because it appears to be the most common one.
It is most common for multiple reasons. What we're, again, measuring is that average variability across that time span.
And what that represents is the input of the vagus nerve, the parasympathetic system, and its input into that sinoatrial node of the heart. Because fundamentally, the autonomic nervous system is governing that heart rhythm.
And primarily what happens at rest is it's that parasympathetic system via the vagus nerve. And the way that it works is it's innervating that sinoatrial node in the heart and it's pulsing in beat with respiratory processes.
So as we inhale, that vagus is inhibited and you get kind of this acceleration of heart rate. Actually, I should back up.
If you were to cut out the autonomic nervous system, you'd have roughly an intrinsic heart rate of about 100 beats per minute, somewhere in that range. Let's back up even a little further, Joel.
I think there's a lot that you and I would take for granted here. So sort of nervous system 101, we have two nervous systems, broadly speaking.
We have one that's under our control and one that is not. Most of what you and I are doing that people can watch, the movement, speaking, all of these things, that's voluntarily under our control.
But what most people can't see when they're looking at themselves is how many things are happening without any input. And thank God for that system.
That system happens to be called the autonomic nervous system. Without it, we would forget to breathe and we would die.
Our heart would stop beating. So all of these vital functions from respiration to heart beating to regulating blood pressure to digesting have to happen via a nervous system that we never think about.
That system's further subdivided into the two terms you've already brought up, a sympathetic system and a parasympathetic system. And you've already alluded to one of the most important nerves in that parasympathetic system called the vagus nerve, which is a cranial nerve, so originates from a very primal part of the brain.
And we won't necessarily get into all the neurotransmitters involved in these things, but what you're basically describing is that the heart is under the influence of both of these. Exactly.
An example that gets to your point is after a patient has undergone a heart transplant, as an extreme example, that vagus nerve is transected. Their heart is no longer under that control therefore, it's just going to have...
And you would see heart rate variability basically zero in that scenario, because it would just be like a metronome. Yeah.
Okay. So didn't mean to interrupt, but I think that might be just helpful context for people to sort of understand what we're talking about, which is you're talking about, even though that person's heart is beating at 60 beats per minute, there's still a very fine interplay between what the sympathetic nervous system is doing and what the parasympathetic nervous system is doing.
Yeah, we should probably even back up a little bit more. The whole reason that we need this autonomic nervous system is to keep us physiologically within these normal ranges that we have to be in to be able to produce energy and stay alive, right? So if our blood pressure goes too high or too low, if our blood glucose gets too high or too low, if our body temperature gets, all of these things have to be within physiological norms, and we'd call that homeostasis, that the internal environment has to be controlled at all times, regardless of the external environment.
So whatever temperatures we're in, whatever we're eating, whatever we're doing, we have to be able to regulate internally and stay within these physiological norms that are necessary for survival. And that fundamentally is what the autonomic nervous system is doing.
It's keeping us alive and it's trying to match the internal demands with whatever we're trying to do given the external environment. So like you said, people have heard of probably these two branches, the sympathetic, the fight or flight or the parasympathetic, which people call rest and digest.
Now, that's a good terminology to understand, but it makes us only think of the sympathetic. Yeah, it's not nuanced enough.
It's not nuanced enough. It also makes us think the sympathetic isn't doing anything.
Unless you're under stress. Right? It's not really like that.
These things aren't binary. They're not switches that turn on or off.
A better way to think about these is dials that the brain is constantly manipulating. And fundamentally, what the autonomic nervous system is doing is twofold.
One is it's sensory. A lot of information has to go up to the brain to process what the internal environment status is.
And then the brain has to make decisions and push motor action down to the different organs to make sure that they're doing what they need to do, given the state of the body, given its external relationship with the world. So fundamentally, the more we can regulate our internal environment and match the demands of our external environment, like the healthier we're going to be.
We're going to be more adaptable. We're going to have better overall function.
We probably would just say it's broadly better health. And so the interplay between that sympathetic and that parasympathetic and making sure they can do their jobs appropriately is a really big piece of making sure that our bodies are going to stay healthy as we age.
Because I would say, fundamentally, if we look at aging as a whole, we lose adaptability. We lose the ability to respond to workouts as quickly.
We become more likely to become injured. When we get sick, it takes longer to get over that.
And that's just the body's ability to regulate itself, declining with age. So anyway, with that said, at rest, we should have very little sympathetic activity going on.
And we can talk about this in terms of waking versus sleeping. Those are different things.
Yes, I want to talk about that. We have a pretty low level of sympathetic just sitting down or laying down.
And at rest, that parasympathetic dial is going to be higher because we don't need this additional energy that the sympathetic system can drive. So at rest, we're primarily measuring that parasympathetic input into the heart.
And as I mentioned, it turns on and off with our respiration it's called respiratory sinus arrhythmia

and as we exhale that dial turns up just slightly and as we exhale it turns down just slightly but mostly what's happening is we are inhibiting that bagel input as we breathe in and we're letting it function correctly or not correctly but we're disinhibiting it as we breathe out and as we exhale. And so you're seeing just this pulsation type effect of that vagus nerve on the heart rate accelerating and then slowing down and then accelerating and then slowing down.
So you're seeing that input pulsing with our respiratory cycles. And so when we measure HRV, regardless of how we do it, we're ultimately trying to understand that tone, we call it vagal tone, that input of that vagus nerve into the heart rhythm.
And that's what we're trying to then gauge as a functional marker of what our autonomic nervous system, specifically the parasympathetic nervous system, is doing. How is it responding to the world around us? How is it responding to what we've done in the last 24, 48 hours? What is its resting tone? How much input does it actually have? And from that, we then try to gain all the other insights we can talk about.
And then just to close the loop on the measurement thing, most people are using devices that are probably calculating the HRV on the RMSSD algorithm. Yeah, most of the commercial ones, yeah.
Yeah, it's a transformation that's basically run on the data. And if my memory serves me correctly, I mean, we could figure it out, right? Root means square or the standard deviation.
Successive squared. Successive squares of standard deviation.
So you're basically going to say average or mean value is X standard deviation is this. And then you probably do a sum square square root of.
Exactly. Yeah.
You get your number. Now, the only one I would say that's different is Apple Watch, actually.
They use what's called SDNN, which is just the standard deviation of the B2B intervals. Why they do that, I'm not sure.
That's one that's historically been used medically, and they'll usually measure it for 24 hours, and they'll just kind of look at, like, do you have any autonomic variation? Does the parasympathetic system function well at all? And it's kind of a gross measure. It's not nearly as nuanced because we're not measuring vagal input at a particular time.
We're just measuring across longer periods of time. And maybe that's why they did that.
It seems to me that that would also introduce a bit of noise because you're combining being at rest with being active. Yeah, exactly.
And you would, I don't know if it's the right word, but you'd be penalizing people for being more active because the more you exercise, the more sympathetic tone you have during exercise, the more you're crushing the variability. Yeah.
And what's interesting is Apple is just kind of measuring randomly for the most part. It just kind of measures when you don't know.
And you can do a manual measurement, which we can talk about, and you can actually check it, which is a better way to do it. But for whatever reason, they've just used this metric that nobody else uses.
And then they kind of measure it periodically when you don't know what's happening. And so the number you're just kind of getting in there, if you're not actively measuring it, is just kind of like, I don't know where it comes from.
So a couple of things that I remember from a AMA that I did on heart rate variability a couple of years ago, and we'll link to it here in the show notes so that people can go back if they want a real primer on HRV. The reason we did sort of an AMA on that was a lot of people had questions about it.
Frankly, I don't think we went into nearly this level of detail about it. We talked much more about the mortality data and things of that nature, but that was one of the first things that stood out.
Two things I remember more than anything, Joel. The first is there was a relationship between, in the research literature, what was measured as HRV, and we should talk about what that means, and all-cause mortality and even disease-specific mortality.
And the second thing that really stands out is a graph that I'll never forget that shows on the x-axis age, on the y-axis HRV, and what the curve looked like. And I couldn't

believe how steeply it declined, right? And I think what it was plotting, if I'm not mistaken,

was kind of mean or median HRV with a band of, call it the 80% or interquartile range or something

like that. But it was an unmistakable trend, which is like a 50-year-old's HRV is less than half of a 15-year-old's.
And it just keeps getting further and further crushed as we go down. I suppose that speaks to what you said earlier, which is one of the hallmarks of aging is this sort of lack of resilience.
And we see it on every level, but this is just a very notable example, which is even at the level of the autonomic nervous system, we lose the ability to recover from insult. And life is an insult.
Everything in life is an insult. The world around is this insult to insult time.
It's just we can respond much better to it as we're younger. Yeah.
Do you have a sense, by the way, of what it is physiologically at the cellular level that is resulting in this profound reduction in HRV as we age? They've looked at this and I don't know that we have a great answer for the exact physiological mechanism. We know it's tied to mitochondrial density, mitochondrial function.
We know it's tied to elements of the immune system. We know it's tied to hormonal status.
And we obviously see decreases in all those things as we age. You just have to wonder which ones are causal and which ones are the response.
I don't think we know that, but we definitely know that we can increase our age of year. We can at least prevent the decline most effectively through cardiovascular fitness.
We see people with higher VO2s have higher mitochondrial function. They have higher VO2 that leads to, or at least correlates with greater HRV.
So we know that cardiovascular fitness in general seems to be the most closely tied to average HRV. There's also a pretty strong genetic component, which we can't ignore.
We can talk about that. But yeah, if you look at the Hallmarks of Aging paper, which I'm sure you've seen, they kind of take these buckets of things, right? They say, oh, as you age, you get dysbiosis, you get deregulated nutrient sensing, you get senescent cells, you get stem cell exhaustion, you get mitochondria.
They list all these things that happen as we age, and they kind of look at this prism of what's the output. And if you read that, they say, okay, the output to the major things are loss of resilience to homeostasis and lack of a stress response that's appropriate, given the world around us.
So yeah, where that cause and effect and which one's causing the other is tricky to say, but I think fundamentally aging is this progressive loss of adaptability. And there's multiple pieces to that obviously, but we're measuring that as you've mentioned is one of the things that we want to gauge of HRV is how much of that resilience of that adaptability are we losing as we age.
And that's something we can influence through lifestyle and training and everything else that we're trying to do here to prevent that slowdown. One of the things in that AMA that I didn't get a great answer to was how much genetics played a role on this.
But from our patient population, because even though that's not a huge N, we've got years and years of seeing these data in patients where every single one of them is using some sort of device. By the way, it's even devices we haven't talked about.
If you look at really high-end things like mattress covers and things like that, like the Eight Sleep will now measure that quite accurately. From every form of wearable and out, you've got endless streams of data and there's an unmistakable difference between people.
There are some people who, and let's just talk about this in RMSSD. We should talk about the other numbers because you have to do this apples to apples.
But if we just talk RMSSD, I've got patients who live at 100 and a good day for them, a good day for them, quote unquote, they're at 120 and a bad day for them, they're at 85. But if you follow them for five years, their average HRV is going to be 100 milliseconds.
I've got other patients whose average HRV is 15 milliseconds and a good day for them is 25 to 30 and a bad day for them is 10. How could that be explained by something other than genes? It isn't.
I mean, I've looked at a bunch of this research just to understand, and it's all over the map, depending on what paper you're looking at, depending on which metrics they calculated. They say genetics is somewhere between like 15 and 70-something percent of HRV.
There's just such a wide range in the research of what you see. Where the exact number falls, I'm not sure, but you definitely see a very strong genetic component to it.
Why? I don't think we truly understand that. But as you mentioned, I see people who don't work out at all and they come into the gym or they, whatever, and you look at their numbers and you're like, you have a very high HRV that you would not expect because you clearly don't have a very high level of cardiovascular fitness.
But I'll say kind of as a whole, if you start talking to those people, they tend to have a healthier family history. They tend to have better health markers.
I think there's something to that and that higher HRE probably still correlates to a health benefit, even if it doesn't necessarily come from exercise-derived means. It's just a genetic thing that they have that probably confers in benefit.
Would you put HRV in a comparable bucket to VO2 max in terms of the following? Amount of it that is genetically determined, amount of it that is modifiable, and the role it might play in understanding overall health status. For VO2 max, I know the answers to all those questions, right? There is a genetic component.
It's not huge. It's probably closer to that 15% than 70%.
It's highly modifiable, but difficult. And the fact that it's highly modifiable, but difficult to modify is why I believe it is, you know, and you've probably heard me say this, the single greatest predictor we have of mortality.
And if there's a better one

out there, I'd like to hear it, but I haven't seen one. And I think that's because I always talk

about VO2 max is like the integrator of so much hard work. You can't cram for the test.
If your

VO2 max is in the top 1%, you weren't born there, you blood, sweat, and tears your way to that.

And all that work does so much good for you. Okay, so let's use that framework to evaluate HRV.
How genetic is it? How modifiable is it? And are the modifications you have to put into it then speak to, hey, if somebody improves their HRV by 50%, how confident are we that that moves the needle in terms of what actually matters, which is not the silly number, but actually the outcome of their life? No, I think it's more genetically based just from what I've seen and probably a bit less modifiable. I would say it's less predictive in the sense that if I have somebody who's got an HRV of 110, to use your example or whatever, and then I have someone who's got a VO2 max I know is, I don't know, 70.
I can pretty well know that person with a VO2 max of 70 is pretty aerobically fit and they've lived a pretty solid lifestyle and had done the work and the training to get that level. I'm more confident in that that person's longevity be fitted and affected from that, that I'm confident in somebody who has no workout history that just has a high HRV.
I don't know that I can say the same confidence at all, just because they have a higher HRV, that they would have the same prognostic value in all-cause mortality. So it's a metric that we aren't gauging output from.
We're just measuring this internal physiological state. And I think that confers benefits to someone who has higher HRV, but I can't necessarily just look in that number and say, oh, this person's really healthy or this person's really fit necessarily because you do see that much stronger genetic component.
Now, if I see a coupling, if I see someone with a higher VO2 and I see higher HRV, chances are that's a reflective of all the things we just talked about, a healthy lifestyle and a lot of hard training and the physiological changes that come as a result of that. And we're more confident that those numbers are going to line up with all-cause mortality.
So a nice way to interpret that, Joel, would be the following. As much as people are worrying about their HRV and people really do worry about it, you should worry more about your VO2 max because you have more control over it and it's a better predictor of all-cause mortality.
I think that what gets measured gets managed, right? And because HRV is so ubiquitous and it's so spit out, and basically you're at the point now where if you go get a Starbucks, they'll tell you your HRV, that they've somehow inferred from the pressure your lips put on the cup. I'm being facetious.
Everybody is inundated with these data and it is creating a lot of stress. Yeah.
I think we want to look at output measures. VO2 max is the best output measure.
We can look at something like heart rate and zone two. Heart rate recovery.
Heart rate recovery. We can look at actual output measures because at the end of the day, I fundamentally think that's what matters.
As we age, we need to be able to continue to move and we need to be able to continue to be able to respond to our environment around us. And output is where we can see those metrics.
What's the metabolic cost for us to move around? If we can maintain movement as we age, we can be highly active. If you look at people that you know around you, they're healthy and older.
A lot of them, they're very active. They move around.
They have hobbies. They have friends.
They're social. They do things they love.
And that's a big part of keeping them healthy and resilient. If we don't have the metabolic capacity to move, we've declined a lot faster.
And so again, VO2 max and heart rate at different speeds, that correlates the ability to move and maintain that as we age. That's far more predictive, I think, than just an internal metric that is important, but does not have the same predictive power.
Do you have kids? I don't. So anybody who's got kids, especially young kids will appreciate this comment, but I've become so much more cognizant of a metric I would love to introduce to the world that ties into what you're describing called spontaneous movement.
I'm an old guy, and even though I'm fit for my age, I don't waste a lot of movement. So I'm already at that stage in my life where I actually think of myself as quite lazy.
So I love to exercise, and obviously I'm not lazy when I'm doing that. But if I'm walking through the airport, I'm just walking.
I will use the stairs and not the escalator and all that stuff. I get it all.
But like, if you're with my kids and my two boys are six and nine, the amount of spontaneous explosive movement is something I don't remember doing as a kid, although I'm sure I did it too. But it's really a remarkable thing.
And we also have a puppy. So we have this puppy that also is bouncing off walls.
But when you see older dogs, that's done. A 14-year-old dog is not, even if it's in good health for its age, it's not bouncing off the walls.
Whereas that puppy can't stop moving. And the same thing, like when I look at my boys, like everywhere we go, they have to race.
Everything is a race. They're sprinting there.
So if we're walking somewhere, they're doing sprints to and from us the whole time. I just think a there's something's something beautiful about that, but I think it speaks to this idea of youth.
Youth is about movement. It is converting the chemical energy of our food into the electrical energy that powers muscles, and spontaneous locomotion seems to be this.
So, I don't know, at some point, I would love to know, is there a way to take that as another output metric, which is GPS on somebody exactly like what is the drive to spontaneously move for no apparent good reason? We talk about we lose HRV, right? But we also lose sympathetic drive to we lose some of that ability to turn that sympathetic dial up as we get older too. And probably it's as we've lost both of those capabilities, the ability to turn that sympathetic dial up and crank out more energy and produce adrenaline and cortisol.
Is that what you think explains the fall in maximum heart rate? Part of it is loss of contractility of the heart, loss of contractility of the musculoskeletal system, loss of hormonal release as a result of the sympathetics. I mean, you're just losing, again, this adaptability, this ability to turn those two dials as necessary to meet whatever demand you're placing the body we can't turn that sympathetic dial up as much we don't have that spontaneous energy that you just described to get up and sprint because that's that dial was way slower and it probably can't go up as high yeah so it's like we were born with a zero to ten rheostat or dial on both of them and as you age that, that 10 goes to a nine, eight, seven, six, five, and you can still move them, but you just can't move them as much.
Yeah, 100%. I would call it autonomic range.
And that really kind of represents what is our body capable of from an energetic standpoint? How quickly can we turn that dial up? And then conversely, how quickly can we turn that dial back down and crank up that perishympathetic side to homeostasis and get our bodies back to normal? And it's interesting if you look at, I've looked at a paper where they looked at different Navy divers that were going through this qualification school, which is kind of their equivalent of SEAL training and, you know, Hell Week and all that. And they tried to pick out what are the variables that separate the people that are really good at this and succeed and make it through versus the ones that don't.
And they measured HRV throughout the process. And essentially, they find what I just talked about is this autonomic range where they could really crank up the sympathetic system when they needed to, and then turn it off as soon as the stressor is over and respond in the other direction with a much higher parachempathetic response.
That ability to use those dials quickly and in the right combination seems to be a really key thing to, again, adaptability. And as we said, if you age, if both of those dials lose their range and they lose their coordination to some respect, then we have much less resilience, much less adaptability.
And we should mention too, as you pointed out, the vagus and the sympathetics, they do influence behavior in a lot of ways. There's a whole thing that's outside my lane in the psychosocial aspect of this.
And you can look up the polyvagal theory by Stephen Porges. But fundamentally, the brain regulates emotion through autonomic function in some capacity.
And the vagus is related to social behaviors. It's related to cognitive control in different scenarios.
It's related to all sorts of stuff. They call it fight, flight, freeze, all these things related to how our autonomic nervous system is influencing our emotions.
And if we don't have the autonomic range, we probably have less drive to get up and move around as a result of that, as those nerves in the autonomic system changes what it can and can't do. I don't think that should ever be underestimated or understated.
I think, again, just even looking at a sample size as small as our patient population, I think we see that a lot. I think there's a very clear association between an individual that, if you just look at them from a movement and exercise perspective, has a very difficult time relaxing.
And relaxing sounds like such a silly word, but I mean that in a sort of a clinical sense. If they can't let their rib cage down, if they can't properly generate intra-abdominal pressure, if they can't go through a sequence of movements that generates some amount of motor control and compensatory relaxation contraction, I think there seems to be very high association between that and emotional stress and psychological stress.
100%. And actually pain as well.
So I think we see chronic pain. And again, you could argue,

well, where's the chicken? Where's the egg? If you're in pain, does that lead to more emotional

stress? Does that lead to an inability to regulate relaxation within the body,

which further exacerbates pain? It's a very vicious cycle.

And you see lack of sleep. Older people need just as much sleep, but they have a harder time getting as much sleep.
And sleep is very much tied to that vagus nerve and the peristymic nervous system. So again, if we get worse quality sleep, we get less adaptability.
It is chicken and egg. But fundamentally, that's why we want to regulate ourselves correctly.
And that's where exercise, I think the biggest thing exercise does is improves our body's ability to regulate itself. It improves the use of those dials because we are exposing the body to the aerobic training that we know has some broad correlation to that.
And we're giving the body a stress it can adapt to in a positive way if we do it in the right amounts. And that's the caveat there.
Before we leave the measurement thing, I want to go on to another one or two of those measurement. At Morpheus, what do you guys use to measure? So we use RMSSD and then we use log natural transform and a multiplier.
That sounds like a lot of math, but essentially if you look at the data of RMSSD and you look at like a normal bell curve, it's skewed. It's non-normal.
It's all the way to the left. So you get these normal ranges of 20 to 80 or a hundred, like you said, but then you can get elite athletes, 180, 200, and see this big bunch of data on the far left-hand side.
It's kind of hard to interpret. So again, I'm not a statistician.
I didn't create the formula, but essentially to normalize this data and make it look more naturally distributed, more like a normal bell curve, you do this log natural transform, use a multiplier and morph it ends up on a scale that looks more like a hundred point scale. So people with lower HRV are going to be more like the 50, 60 people with more moderate 60, 70, higher 70, 80 elite athletes are going to be 90 to a hundred.
It's more of a scale that we have a more familiar relationship with, I would say. And the data is more normalized from a standpoint of a bell curve.
So it's just an easier to interpret, but that's the reason for it. So to most people, when they start using Morpheus and they're also using whatever other device they're using, that's just a purely RMSSD device, how much discordance are they typically seeing between them? It really depends on what they're using.
It can be a big difference between the device that they're using and the numbers they're getting, but the trends should generally line up.

If you're seeing Morpheus increase as a whole, you should see the other one increase as a

whole.

You should see the directional change matching, but the actual numbers will be somewhat different

depending on where you're at in that spectrum.

Let's now talk a little bit about Morpheus.

I've alluded to it a couple of times.

So it's a product I've been using for about a year and a half, maybe close to two years.

But before I talk about my experience with it and what... of times.
So it's a product I've been using for about a year and a half, maybe close to two years.

But before I talk about my experience with it and why I use it, everything I do, I do for a reason.

I'm a very deliberate human being. So there's a very particular use case that is pretty narrow for how I use it.
I know that I'm not using it to its full potential, but tell folks what this is

about, your involvement in this. And that's obviously how we got to know each other.

Yeah, I mean, when I started using the old system, I had to wait for people to come in the gym to measure them. And so I realized I was getting a pretty small snapshot of what their life story was because I might measure them two or three times a week.
Sometimes they come in the morning, sometimes they come in the afternoon. And I realized the limitations of that.
This is back in 2007 or eight. And so I wanted to create something that people could use their phones and that we could get way more data from.
And that was my first system bioforest HRV 2011. And that was really one of the earliest HRV apps out there where we could take your phone, you could do a recording and you could get your HRV on your own.
You didn't need to come into the gym. And one of the limitations of that was all I could look at was your HRV.
I didn't necessarily have any idea what else was being tied to that. And so I could look at the change and ask you a bunch of questions and maybe try to figure out what those changes were coming from.
But I wanted to create something that also tied in training and sleep and subjective markers and other metrics so that as a coach, I just had a more complete story of what was happening. And so that was really the genesis of Morpheus.
And I started that in 2016, 2017. So quite a few years ago.
And basically what we're doing is we're measuring HRV and then we're tracking activity, sleep, workouts, all that sort of stuff. You can use the Morpheus device for a lot of that, or you can use other devices.
So if you're using an Apple watch to track your activity, your sleep or Garmin, we'll pull that data in. But what we're trying to do is take that HRV.
This is something we should definitely talk about. There's a lot of apps that give you HRV.
And then you can either say, okay, I'm gonna interpret what this means myself and I can try to figure out what these changes are. It's a physiological metric.
Or you can say the apps are giving me a recovery or a readiness or some gauge that's based on that. Now, this comes back to every app's doing this completely differently.
We have a lack of standardization across not just the HRV measurement, but then how that information is interpreted to generate recovery or readiness or some sort of number that the person in the app is saying, oh, my recovery is 80% or my readiness is... These are just numbers that we are creating as a way to try to interpret the data.
And then some of those apps, I think, do a reasonable job with it. Some of them don't.
But I created Morpheus and this idea of the recovery score based on what I had seen using HRV for 20 years or maybe 15 years at that point. It's just a metric of what's appropriate for you on a given day.
What is your body more likely to benefit from? And so we should probably talk about again, what is recovery? What is readiness? Because those are metrics that Morpheus gives you and Ura gives you and Whoop gives you and Garmin gives you like a body battery or every kind of app has their own gauge of that. But then the question is how accurate is it? What does it really mean? And I think that's where a lot of confusion also comes in because we're trying to take metrics and turn them into something that's not a physiological measure, but something we try to create.
Yeah. I mean, look, I used an Oura ring for many years, probably haven't used it in a year, year and a half.
There's better devices I can use to track my sleep now. And the recovery score, as you said, even if you believe the score is accurate and there's no reason to believe it necessarily is, more importantly, it's not something you can act on.
Let's just say you believe the number and you say, okay, my recovery score is 80 today. I certainly believe that if it spits out a 90 versus a 70, your whoop or aura, there's probably a difference there.
You're probably better off on the day you're 90 than the day you're 60. But how do you operationalize that information?

And so when I was introduced to Morpheus, it was actually someone on my clinical team that said, we're having a hard time giving people real instruction around zone two, because most people don't want to do what you do, Peter. Nobody wants to check their lactate levels and go through this.
And I get it. I'd never fault somebody for not wanting to do a finger stick every time they do a workout.
And truthfully, for some people, just relying on RPE can be challenging. So this person said, hey, look, the Morpheus app, and we'll talk about how it works.
I also appreciate how the measurement is taken. The Morpheus app gives you target zones for heart rate every day.
And if you use the cutoff between what it's calling zone one and zone two, that's a pretty good proxy for what your zone two is on that day. So I bought the system and started using it and I should show you the data because I have recorded every single workout I have ever done for the last year and a half.
And I record the following. I record the heart rate predicted by Morpheus for what my zone two is, the heart rate I largely end up at by RPE, and sometimes they're close.
Usually they're quite close. Sometimes they're quite far.
So sometimes Morpheus tells me to be at 138, but I'm kind of gassed out at 131, and sometimes it's the reverse. Sometimes Morpheus says you should be at 133, but I feel fantastic.
And I go to 140. What the power was for the interval and what the lactate is.
And I have to tell you, Joel, I cannot put in words how impressed I am with that system and how remarkably accurate it is at predicting something that is very difficult to predict. So kudos to you for doing that.
What I find amazing are the days when, and I had one of these days a week ago, Morpheus said I should have been at 140 or 139 for zone two. I got on the bike and I did not feel great.
And I sort of said, I think Morpheus got it wrong. I'm going to ride to this wattage.
And my heart rate was about 132. And I checked my lactate and it was 1.1 millimole.
I was nowhere near my limit of where I could have been that day. Now, again, we could get in the weeds on, maybe that's fine.
Maybe that's all I needed that day. And maybe I should have just been following how I felt.
But if I'm really trying to get the right training effect, I was under training a little bit on that day. So I'll kind of pause there because I want to kind of let you sort of interpret what I'm saying.
And why is it about that? Because you spit out three zones, zone one, zone two, zone three. And I think you call them recovery and conditioning.
Yeah, it's just terminology, right? It's just a way to gauge low, moderate, high intensity, more or less. Does it surprise you? Because I haven't told you this story before in all of our communications.
We've never talked about this particular issue. Does it surprise you that the heart rate that is on the cusp between your first and second training zones happens to correspond to this lactate of two sweet spot? I mean, that was really the intent when I designed it.
And that's probably that's difference in Morbius, I would say, is when I designed it, it was as my experience as a coach for many years of testing lactate, of VO2 max testing, of HIV testing. I synthesized a lot of information that I gained and knowledge and insight I gained to create this structured system of low, moderate, high intensity.
You can call them whatever you want to call them. That's basically what those zones are.
And the biggest thing I realized is as people's autonomic nervous system changes, intensity and heart rate changes. And you learn this over time when you see today 140 is doing this and tomorrow 140 might be doing that based on changes in the autonomic nervous system.
And so when I created the algorithm, it was just based on a lot of data collected over a number of years of what I'd seen in the gym, what I'd measured, what I didn't look back at the data. And so that was the end result of Morpheus was trying to translate changes internally with how we can then turn that into smarter, more accurate and precise training.
And that's what you're seeing with Morpheus. So it's awesome to hear that it's accurate for you.
And some people, it's always going to be much more accurate than others. But as a whole, Morpheus is by far the best way to translate, again, changes internally with changes we should be doing in the gym.
Yeah. I mean, basically for our patients now, we almost never bother with them checking lactate.
It's basically RPE if you can manage it, if you really have a sense of what zone two feels like, great. But if you want some guidance, look, take the Maffetone formula 180 minus your age, great place to start.
Once you're getting a little more nuanced, if you want more guidance, use Morpheus and go to that heart rate. Again, tell folks how I get that number every morning.
How is it spitting out that number for me? I have to do a measurement, right? Yeah. I mean, you have to measure your HRV and then we're looking at other things that you've done in the past 24 hours if you're recording it.
And then based on your fitness level, so we ascertain your fitness level by looking at your resting heart rates, by looking at your average HRV, by looking at some of your heart rate trends when you're training. And we say, okay, Peter's roughly at this level of fitness.
Peter's autonomic nervous system is responding in this way, which again correlates to how it's going to react today. If I'm fatigued, then it's going to take more energy to produce the same level of power output.
And then we estimate, like you said, what for you is this cutoff between low intensity, moderate intensity, and high intensity. And a way that people can think about this, I would say, is muscle fiber recruitment.
So low intensity is primarily slow twitch muscle fibers doing the majority of the work. And specifically, if zone two, we're talking about where they're mostly oxidizing fat as much as possible, kind of this moderate intensity, we're starting to recruit some of those moderate threshold fibers.
And we can talk about what that means. But we're starting to recruit some of those faster twitch, higher threshold muscle fibers.
And then higher intensity, we're starting to really all the muscle fibers and the highest intensity muscle fibers and so as morpheus is looking at this it's basically saying okay roughly this heart rate we think this is a level of intensity that is going to correspond to these low medium and high and then it's giving the ability to just plug in morpheus and say i want to do zone two morpheus says okay based on what we've seen this is where we think your zone two is for you today. And so on the same thing.
Yeah. And again, I just want to reiterate, this is why it's very valuable.
It's actually giving me the prescription every single day. When I got it, I was a little surprised.
You know, I sort of bite at sight unseen. I was just kind of told it's valuable, but I didn't understand the nuance.
So the thing shows up and I realized, oh, every morning I need to do a two and a half minute lay down in bed before I get up, still test, measuring my heart rate. I guess you can do that.
Morpheus at the time came with a chest strap and an armband. I think now it's just a chest strap.
You put the chest strap on in bed. You lay there.
You answer a couple of questions. It wants to know how many hours did I sleep the night before? So I pull that data off my sleep tracker, my eight sleep.
What's the quality of my sleep? I'm pulling off that as well. And then I think it's saying, how sore am I subjectively and how good do I feel? Yep.
Just subjective markers. Those are actually reasonably validated markers for training performance.
They are. And then I measure, I lay there and just kind of do nothing, meditate usually.
And it measures my HRV and heart rate. And then it spits out, here's your HRV, here's your heart rate, here's your, basically your recovery score as a percent.
And then here are your target training zones, which then come up again when you train that day, it's already loaded into the app. So your training zones change every day.
So one of the things that surprised me, Joel, was like, wait a minute, I'm used to having to measure HRV over the course of a night. What is the difference between what my aura ring used to tell me by measuring over eight hours of sleep versus this thing that's telling me in two and a half minutes in the morning before I've gotten up.
This is probably the most important part of HIV because there is so much confusion in this. We look back historically at all the data that's been used, these all-cause mortality studies and all the different pieces of literature out there, 95% of them are from spot HV measurements that we are measuring at a specific time.
And you're doing this in standardized conditions as much as you can to get a baseline. Because we want to know where is your system? Same time every time.
Same time every day, the same conditions. Because what I want to know is last 24 hours, you did something yesterday, did lots of things, I assume.
You ate food, you maybe worked out, you maybe had alcohol or maybe you didn't. You did mental stress or maybe didn't.
You put your body in a situation where it had to respond for the majority of the day to do something. And then you went to bed.
And we want to see the result of that. We want to see this stress and recovery cycle that you went through yesterday, because that tells us where your body's at right now.
How is it responding? Because we'll look at changes over time and understand how your body is adapting to the world around you. And that's what most HRV has been built on is we measure in standard conditions.
We see where you're at today. And that informs us about what happened over the last 24 hours and maybe slightly beyond.
And the analogy is if I was going to weigh myself, I'd want to weigh myself first thing in the morning in standard conditions. I wouldn't want to have a meal and then go weigh myself.
I'd want to have very standard ways of measuring so I can see the changes because ultimately it's you changing against yourself that's the most informative. So we wake up, we measure HIV, we see where you are and we see where you were, what your averages have been, what your variations have been.
And that tells us where you are today. And that helps us make a decision about what are you ready to do right now? What's the most appropriate for you to do right now? One thing I'll say is, if your HIV is high or low, we can talk about what those mean.
It doesn't mean that you can't train hard. It just might mean that like, that might not be the most beneficial thing for you.
And there might be a cost associated with that. If I wake up, my HIV is way outside of normal.
You can't say, oh, I can't work out today. You can.
It's just a question of, is that what your body needs? Yeah. To be clear, I don't think I've, I mean, I don't think I have never once not exercised as a result of what that said.
And there have been days when I've had abysmal scores and it's told me like my heart rate range on what it has told me is never above about 141. There have been days it's been as low as 121, which for me, it means like my recovery was 35 or 40%.
That's a night when I didn't sleep and something was dramatically off. You'd still do the workout.
You just are aware of what the cost of that workout will be. You might make adjustments tomorrow or through your plan.
That's what we're getting when we're measuring at the end of sleep. The morning time we're seeing what was the result of our sleep, what was the result of our workout.
So yesterday, everything else we did, if we're measuring HRV overnight, HRV number one is always higher at night because the parasympathetic system is that dial is already turned up quite a bit because you're sleeping where it's the highest. Although for most people, Joel, they will see the reverse.
Likemssd hrv overnight is lower than the log normal transform i get out of morpheus yeah because morpheus if you look at the actual rmssd data you would see that you'd be higher and i know morpheus is different obviously and can we see that in the app you can't right now we've honestly when we first came out with bioforce and morpheus there weren't so many other apps to compare. So it wasn't as big a deal to not show the raw number.
So we chose not to, but now I think we probably will just because people do want to compare. But anyway, overnight, that dial of that parasympathetic system was already higher.
So we're getting less of a responsiveness to see what actually is changing at rest. We're not measuring at rest.
The second thing is if you have arrhythmias, if you're an athlete who has very high HRV, you don't have as much variability. We're not really gauging the true responsiveness of the 24 hours before.
We're measuring more of what's it doing during the recovery period, which has some correlation, obviously, but we're not really seeing where are you at the end of that recovery period? Where are you ready to go today for this next period of stress? And here's the biggest thing is if you do something, if you do a workout in the evening, if you have a few glasses of wine, if you're doing something very mentally challenging, the first part of your sleep, you're just responding to that. And so your HRV is not reflective of this whole process.
It's just reflective of, hey, you just did an evening workout and your HRV is still suppressed for the first half of your sleep responding to that workout. So we don't get a true picture of where am I at right now and how does that correlate to what I should be doing for the next 12 to 18 hours as I'm awake across the next day.
So I think we're just probably getting a much better gauge of sleep and how our body is responding during sleep, but we're not really getting this true picture of how did our body go through the whole process of life, sleep, recover, next. We don't see that picture as well because we're not measuring at the end of sleep, we're getting this average across it.
So I don't think it's telling us really the same thing and it doesn't have the same utility for telling us from a workout perspective, what's the most appropriate thing for us to do. Might be a silly question, but it occurred to me now as we were talking about this, the one fundamental difference from one day to another in that morning check for me is there are some mornings I wake up and I have to pee so badly.
And there are some mornings when I don't. And there's a part of me that's wondering as I'm laying there doing my test while needing to pee, is that putting a little more sympathetic tone into this? Am I getting a skewed measurement? Would I be better off going, peeing, coming back, waiting a few minutes? I'd go to the bathroom and get up.
It's not that big of an issue if you just go up, go to the bathroom, you come back and you reestablish. And part of that's actually measuring how well can you reestablish that.
If that significantly impacted your HRV, it probably was on the lower end to begin with. But it does bring up a point.
I should mention, people with really high HRVs, I don't think this becomes an issue, at least in morphine until you're in the 90s or resting heart rates in the low to mid 40s. Your HRV is already very, very high that laying down, you're taking some of the responsiveness away.
If you start getting to those categories, you probably want to take it seated. The challenge for most people seated, they get antsy, they move around, you introduce more motion artifacts, and it becomes more difficult.
But we really want to have as much range that dial available as possible because we want to see how the nervous system is turning that dial. So if you're very high, like I said, I would say someone who's resting heart rates.
Yeah. I'm never above the low eighties is as high as I get.
I think at that point laying down is still a good way to take it. But if you get up in the nineties, mid nineties, you really want to maximize that potential responsiveness.
And that's where a seated measurement makes more sense, but that's a fairly small percentage of the population that's going to be up in that ranges. RMSD, you're talking 120s, 130s, 150.
When you get up in those ranges, you probably want to take it seated. Okay.
When I bought the Morpheus a couple of years ago, you had an armband and a chest strap that came with it. So I still use the armband as my morning check.
That way I don't have to move them back and forth. It always sits right there.
And then I use my chest strap when I'm exercising. You've gone to just a chest strap.
Is that because you think you're going to get better data and it's just better to have people using the chest strap for both? And should I do the same? I mean, it's two things. I don't think the data, as long as you're measuring consistently and you have the chest or you have the armband placed correctly, that's not any less accurate.
I don't think the problem we ran into as people, as you know, are trying to use our armband to train because it's more convenient. Like, Oh, the armband is, it goes to my wrist and their workout data was just not as accurate.
The second thing is it looked like a watch, but it wasn't a watch. And so we had a bunch of confusion with people putting it on their wrist and not sure what to do with it.
It just created a lot of confusion. So at the end of the day, I said, look, the chest strap is giving us the best data.
It's unambiguous. If people really want to wear an arm device device because they just don't want to put the chest strap on, we work with the Scosche Rhythm 24 because it uses the exact same sensor that Morpheus used in our original armand that you have.
And so if they want to do that, they can measure it that way. But from an accuracy perspective, from both the HRV and the workout, it just made sense for us to standardize that, use the chest strap and make it as universal as possible rather than try and sell two devices, which people were ultimately somewhat unsure of.
Okay. So let's talk a little bit about the question that I'm sure is on everybody's mind, which is I've been doing this for a while and I get that at the individual for my data, I see my up and down level and I know that, hey, when it's higher, I'm generally going to perform better and I can push a little harder when it's lower.
I'm probably not going to perform as well and maybe need to make that a little bit more of a less hard day. But then you get this question of, hey, what can I be doing to improve the quality of my health in a way that is measured by this output of HRV? Sure.
I mean, this is where HRV is driven by genetics, fitness, primarily cardiovascular fitness is the biggest thing we see in quarterly and drive it. And then obviously lifestyle.
Doing things in your lifestyle that make that sympathetic dial come down when you don't need it and doing things that turn on that parasympathetic dial when you're not using this is going to put you in your highest level of your particular range from a lifestyle perspective. And that's where I think most people underestimate the lifestyle impact on HRV and training and everything else They don't realize if you're stressed out from work six, eight, 10 hours a day, you're running around chasing your kids, you're doing all these things and you know, your daily life, that's a pretty significant impact on your HRV because that sympathetic diet will be turned up for hours on end.
Maybe not the same degree, of course, as a workout, but hours on end. So a lot of it comes down to just the stuff we know in everyday life that makes us healthier.
Eating healthier foods, making sure we're getting enough sleep, managing our mental stress effectively, doing things that allow us to relax and turn that parasympathetic dial back up and that sympathetic dial back down, and then build VO2 max. So do you think it's more impacted by peak aerobic fitness or by base aerobic fitness? Would you say it's more impacted by a higher zone two or a higher VO2 max? I mean, they both contribute exactly how much, you know, I couldn't say.
We tend to measure aerobic fitness from a peak standpoint for the most part. So that's more standardized what we would look at.
But I think training frequency matters, which is where you get zone two, right? You can't do VO2 max training five, six days a week. We do a lot more zone two.
We do a lot more frequency and volume of that. And I think that translates more than likely into a higher HRV, even if you didn't go out and do a bunch of the zone two or the VO2 max type work.
Yeah. And then one of the advantages I think of those overnight tests, again, whether it's aura, whoop, eight sleep, any of these things is people have noticed how much of an impact alcohol has on overnight HRV.
It's probably one of the most profound changes you see in response to alcohol. And I would argue that a big part of the movement we're seeing around people drinking less can be attributed to those devices, which is giving people visibility into, oh my God, I didn't realize that alcohol could have such a profound impact on this.
I guess that would kind of be out of your system maybe the next day or would that still be there in the morning? It would depend in the sense of if you had alcohol close enough to bedtime, it's going to impact your sleep, which impacts your recovery, which will impact the morning measurements. You'll still see some remnants of it for sure.
But yeah, you'll see that more directly in the overnight stuff. I think as a whole, what we see is people become much more aware of things like alcohol, things like excessive stimulants, or God forbid, smoking, or massive amounts of chronic mental stress.
Those things impact much more than I think people realize. An example of this, we were measuring a college soccer team across a couple of seasons, and we would see that during finals week, they would look far worse than during tournaments,

even competitive playoffs, just because that stress of being in a finals week where you're

studying and you're not sleeping and you're stressed out.

Give me a sense of the range that you would see. Give me an average athlete where this would be their morning HRV under these circumstances.
This is what it looks like when they're over-trained. This is what it looks like when they're in the tournament.
This is what it looks like in finals. Yeah, again, there's a lot of variability there.
But from a college standpoint, most soccer athletes that we would see in these are female athletes would be in the low to mid 80s on a normal basis. And this again, this is Morpheus system.
You can't compare these to other numbers, but they'd be in the low to mid 80s kind of as a normal range. We should then drop into the 70s, sometimes down to 50s, which is in Morpheus.
That's the stress? Yeah, that was the stress of finals week. It's two, three, four days of not getting much sleep and studying a lot and just working out very less or very sporadically, probably compared to normal training sessions, you just see the impacts of life being very, very significant that people don't necessarily expect that because they feel like, oh, the workout's the most impactful thing.
Well, it is in a way, but it's also only an hour, maybe two hours. It's the rest of your life that also adds up to a huge amount of stress if you are very, very stressed.
And if you're going through your life in that kind of type A, I'm always turned on. I can't turn off my stress.
That has a very big impact. I think Sapolsky, who I know you've had on the show talks a lot about the mechanisms.
Like you see that play out pretty frequently when you look at HIV data. I don't utilize the Morpheus system fully because I only wear it during my zone two workouts.
So I don't wear it when I'm doing my VO2 max workouts because I'm already wearing that Polar system because it pairs with the Garmin and it pairs with the other power meters and all the other stuff I'm using. I guess I could double up.
Can you wear two chest straps? I mean, you could. The Polar should be able to connect to the Morpheus app directly while you're training.
But then it would have to pair to two apps. It should be able to if it's got two Bluetooth radios, which which it probably does.
You probably could do that. That would be good to know.
But I don't wear it when I'm strength training. So I realized that I'm failing to give it all of the data because that's another, I don't wear it when I'm rucking.
There's a lot of time I'm active, but I'm not wearing it. So how much am I missing out on in terms of the fidelity of what it might be telling me? And I want to, cause I want to talk about the algorithm.
One of the things you and I spend so much time on is I can't make sense of how it's coming up with the numbers, even though they end up being right. Most of the time, the more data you give it, obviously the better it's going to be exactly how much you're losing, and it's hard to say, but we're measuring the output

with that HRV change

and with the numbers

that you're putting into it.

We know the output of where you are.

We can't always ascertain

how you got there

if we don't have all that data

of the workout sort of things.

But as long as we have

that consistent HRV measurement

every morning

in standardized conditions,

you know, we're still able to

get the vast majority

of what we're trying to get, which is what are you most likely to do when you work out right now? How much is that going to impact you? So that is the most important thing. That's by far the most important thing.
To make sure that every day you see my heart rate, my heart rate variability, how long I slept, how sore I am, and my desire to train. Yeah, that's the vast majority of it.
Because again, it's telling us where you are right now. The readout state.
The readout. That's the output.
We know the output. This is where your body is at right now.
If we can reverse engineer that from the input, we can have some more insight into that. But you're not losing a bunch of accuracy because you didn't get that.
We want the output. We want that as standardized and accurate as possible.
So I would say as long as you're measuring consistently every morning, the same context, same conditions, it's going to be more than accurate enough for what you want to do. Okay, great.
And again, my use case is quite simple, which is mostly just predicting that zone two. But I have a feeling a lot of people listening to us will immediately resonate with that use case.
Because I think for many people, there's still a little bit of ambiguity on not the concept of what zone two feels like, but the day-to-day variation, which again, is really significant. And that speaks to the body's dynamic.
We can do a zone two test and look at lactate and all these things. If we just take one test, we don't realize how much the body changes on a daily basis.
And so if you just, okay, I took my lactate test six months ago, I'm just using the static zone two. You're missing that dynamic change that the body is going through on a daily basis.
The body is not static. I measure blood pressure.
I measure testosterone. All these numbers change constantly.
The body doesn't sit still. And I want to make another point, which is people, again, might be listening and saying, Peter, man, it's too much data, dude.
Just go out there and do it. I'll give you the counter argument to that.
When I was a competitive athlete and I was training 28 hours a week, I had the luxury of junk miles. I didn't always have to be perfect, but I'm not a competitive athlete.
I'm a competitive father. I'm running three businesses.
Like I don't have the time for nonsense. Every minute I'm training, I have to get the training stimulus right, or at least as close to right as possible.
So when I'm setting out to do zone two, I got to do it. And if I'm out there trucking along and my lactates 1.1 or 2.9, I'm missing the training effect I want.
So the more insight I can get to narrow that down, the better. I'm only going to give three hours a week or four hours a week to that training.
I'm not going to put 12 hours into it where if I do 12 hours and I screw up three of them, who cares? I still got nine. So that's why I know that there are people watching this saying, dude, you're a psycho.
And it's like, no, I'm just efficient with my time. And I don't want to waste my time.
I think what it comes down to is each person has a certain amount of training in a week. I think it's a weekly basis because that's kind of the cycle we live in.
There's an amount and a type and an intensity of training that you are individually going to respond the best to. And if you go above it, not so great things are going to happen.
If you go below it, you're not going to get the outpoints that you want. And that amount is not easy to find.
And it changes on a weekly basis. It's not the same week in, week out.
And so the more that you can hone in on that core, how much volume do I need and how much intensity do I need? If you can get that right week in and week out, you will see continual improvements and that work will turn into result. If you don't answer that correctly, bad things happen.
You either waste your time because you're not getting as much out of it as you could, or you do end up overtrained, in which case we see injuries and we see burnout and lots of things that are going to have negative health consequences. So I think ultimately what you said is I want to use information to make sure that I'm getting the most bang for my buck, the best result for the amount of work I'm putting in.
And that's where I think data can play a really powerful role is it's information that you can use to make much more granular decisions around rather than just guessing, oh, I should go do 40 minutes today. Should you? Or I should do 200 minutes this week.
Is there anything to support that other than just throwing stuff at the wall and seeing what sticks? And I think that's what intrigued me so much about HRV is it felt like I could open the black box and get some real answers other than like test, train for eight weeks, remeasure, see what happened. I don't want to wait eight weeks.
I don't want to potentially lose the gains I could have made across that time period. So for someone like yourself, that's again, wanting to get as much out of their time as they possibly can.
Yeah. Data can play a really strong role in that because it's going to answer questions that can't be answered otherwise.
And I think it only gets more significant as we age. 100%.
When I was 40, my recovery capacity was so much greater than now. Nevermind 30, 20, that's obvious.
But even the difference between 40 and 50 is significant. And I know there are a lot of people listening to us right now who can relate.
They're sort of like, hey, I'm getting a little bit older. I don't feel as great as I did.
It's a question of time and age. And I think the further we get along that, the more this type of system, for me, I can't say enough about it.
Age reduces your margin of error. Yeah, exactly.
I mean, I'm 44 and you can do a lot of things wrong in your 20s and maybe in 30s and you can still get a lot of benefit out of it because you're so resilient. Your metabolism will adapt.
But like you said, the older you get, the less you can do that. And so you have to be much more acutely aware of what your body can and can't do.
And that's part of what HIV can help you understand. You said something maybe 20, 30 minutes ago, and I jotted a note down because I didn't want to derail us at the time.
I'll come back to it now. So when I'm doing my VO2 max sets, the thing I monitor for every set is heart rate recovery.
So as soon as I get to the top, because I do those on a hill. So as soon as I go to the top of the hill, I hit the lap timer and I count how many beats does my heart rate go down in the first 60 seconds at the completion of the interval.
And that's a great proxy for how I'm doing. So I've got kind of my normal range should be 30 to 35 on a really good day.
I'm 40 to 45 a week ago or so. I had like one of the worst days I've ever had where I was like 19 to 21 in a minute.
That's all I could recover. I was smoked.
Now I didn't sleep the night before. I made an Instagram post about it because I thought it was just a great sort of illustrative teaching point.
You said something that made me wonder about another test. Would there be any utility in right after a VO2 max interval doing an heart rate variability test to see how much sympathetic tone can I dial down and how much parasympathetic tone can I dial up after what's probably a peak, you know, a very high sympathetic, low parasympathetic exercise.
You can do that, actually. I mean, it's very specific.
Like you can't move around if you want to get some standardization to it. So yeah, you could do a 10, 15 minute recovery period.
What if I just did it right at the top? Would that be too much? Probably. I think heart rate recovery is- Is far better.
Well, it's illustrative of what you wanted to get to because what we see is heart rate recovery is driven by what? The reactivation. The balance of those two.
It's turning the sympathetic down as quickly as possible and turning the vagus, the parasympathetic up as fast as possible. So heart rate recovery is already giving you that information without having to get as granular as pulling out the B2B.
You don't necessarily have to get that level of detail. You can just see the heart rate drop.
And that drop is being caused by the increase in heart rate variability. And what's really fascinating is they used to think, and this is pretty new research I was going through.
We used to have this idea that when your heart rate increased above 100 beats per minute, that there was really no vagus input. There was almost no parasympathetic.
And they figured that because they would look at acetylcholine as essentially they could block it into the heart. And they'd say, oh, we block acetylcholine from vagus and heart still pumps just fine during their exercise.
So exercise must not be vagusly driven at all. But what they found is that the vagus might actually be turned up a bit during exercise in some sense, because it can increase coronary blood flow by increasing vasodilation in the coronary artery and so hrv is probably not a part the vagus i should say is probably not completely inactive probably not completely off it's this ratio it could be turned up but the sympathetic system is turned up so much more and it's using a different mechanism we don't see the heart availability high obviously but it's probably more ready to turn that back up even further as soon as that sympathetic system starts turning down.
And we're dropping our adrenergic hormone levels or catecholamines, all these things are dropping pretty quickly. And the faster we can turn that parasympathetic up, the faster our heart rate comes down.
The other thing that's interesting is they've looked at heart recovery in terms of it represents to some extent the balance of the aerobic and anaerobic systems that contributed to that exercise. So the more aerobically driven something was, the faster our heart rate drops.
Because in a lot of ways, higher heart rates are driven by that sympathetic and by the anaerobic pieces of metabolism. So what do you see in young exceptional athletes? I mean, I wish I had tracked this metric when I was a teenager.
Like I wish I know how much my heart rate recovered then back when my peak heart rate was 205 to 210. What do you see in these young collegiate athletes? I mean, a really good number is 50, 60 from a near max.
So I trained combat athletes, UFC fighters, pride fighters for many, many years, and they have to go into the octagon or cage ring, depending on what they're doing. And they have to fight for three, five minute rounds, five, five minute rounds, probably just a 10 minute round, which is crazy.
So we would use heart rate recovery between rounds. That's a really good gauge.
Because it's one minute between rounds. It's one minute between rounds.
Yes, exactly. And they would sit down between rounds so we could standardize that.
And so I would use that drop as a very good gauge of how well conditioned is this athlete, how ready to go out there. Give me an example of what you would see on a fighter.
They would come out of the previous round at what? They come out 160, 180, depending. I mean, it could be.
Depends what the round was about. Depends what the round was like, right? And the round was slower.
It's going to be much lower. But most of the rounds are between like 160, 180, depending on their age or anything else.
You might see them spike up. And they could drop by 50 to 60.
I would want them to get to 130s between each round. We would simulate this in sparring rounds leading up to the fight.
We wouldn't measure it during a fight, obviously. But if they're doing a simulated fight round where it's three fives or five fives, I'd want them to be able to drop in the 130s between every round.
If we started seeing their first round, they weren't coming down below 150, 160. They're not in good enough shape.
They're not good enough shape. They were going to fatigue every time.
And that just told us they were having to rely so much on the anaerobic piece. They were going to fatigue because at a sport like this, you have to be really explosive, but you have to also have the endurance.
It's about the ratio of energy utilization that matters so much. If you don't have enough anaerobic, you're going to lack power and speed and ability to finish.
But if you have not enough aerobic, you're not going to sustain that explosive power for very long. And so it's really tricky to get that ratio right.
And you see the fastest, most explosive, hardest hitting athletes often fatigue the fastest because they're generating that from the anaerobic side and they're relying on that. And that's great if they can win and they can knock the person out or submit them.
But if they can't and you get in the later rounds, that's where they're going to really struggle versus somebody else who's more aerobically dominant. So that's a really hard part about that sport is getting that ratio correct and training the right side of it.
But the heart rate recovery was such a great way to see that. And so like I said, I would want to see, in sparring at least, you know, there are going to be higher heart rates during the competition from the psychological stress.
But we want to see them drop in the one thirties. Again, this is seated going from standing to seated, but they should be able to get the heart rate back in the one thirties between each round, ideally before they go for a fight.
If they could do that and they were fighting at a high level pace, you knew they were in pretty good condition and they'd be ready to go out and go. If they weren't doing that, especially if the early rounds, if they're like I said, round one, they're at one 50, one 60, you know, they better finish the fight quickly.
They're going to be in trouble. So interesting.
I want to go back to kind of what we were talking about on the trailing average of HRV data. So I'm glad to hear that my failure to utilize Morpheus in every moment of the day isn't really impeding its fidelity.
I kind of know that because,, as I said, it just, it's so damn accurate

in what it predicts. It's like a shaman.
But what amazes me, you have the patience of a saint, Joel, because I email you so much, it must be infuriating. But what amazes me is how sometimes the data I see, I don't believe it.
You're always like, yep, but you got to look back at what it did seven days ago and six days ago and five days ago. And so walk me through the arc of HRV over time and how the undulation of the HRV matters as much as the HRV on a given day.
This is the part that is totally news to me. And again, I think the proof is in the pudding because at least for me, this seems to really work.
Sure. Yeah.
I mean, again, we're looking at not just what is your number, but what is your number in relation to where you're usually at? And we're looking at how much does our number move today versus what's like a normal movement for you? And again, we're looking at just this manipulation of dials by the autonomic nervous system. So what Morphus is doing is looking at your seven days and seeing, okay, what's your normal baseline number itself, but also what's your normal level of variability across those different time periods.
And then we look at standard deviation. And so if we see big changes greater than one standard deviation away from your average, away from your baseline, we know that that's the odd number of your system responding to a greater input.
It's responding to more stress and it's having to make bigger dial adjustments. And that tells us that you've been paying a higher cost because you put your body under more stress.
If we were to probably illustrate to just isolate, our body's in kind of a normal rested state, let's say, and then we do a single workout and we allow it whatever necessary time needs to recover. During the workout, obviously the body turns up that sympathetic dial.
It turns down that parasympathetic dial. We produce more force, more energy, more power, blah, blah, blah.
And then after the workout, like we talked about, the sympathetic system starts to come down. The parasympathetic starts to come back up.
Now, depending on the workout you did, that could happen in very different timescales. And Steven Seiler, again, a really popularized polar training, he was just showing some stuff.
If you do like zone two and below aerobic work, that recovery happens pretty quickly. Within a few hours, we'll see that parasympathetic system turn on and it'll come up above your baseline to maybe 110, 120% of what your HIV was at rest.
So Morpheus, if you were, I don't know, a 70, if you were to theoretically remeasure it, you might be a 74, 75, you would see a noticeable uptick above baseline because our body has been able to shift very quickly into that restorative phase by that vagus nerve firing more forcefully and turning up the parasympathetic. So we see, again, suppression during the workout and the curve starting to come back up.
During lower intensity workouts, we'll see it pretty quickly come up above baseline. And then kind of as your body went through that complete cycle and restored homeostasis and did what it wanted to do, it was going to just kind of settle back down to where it started.
And so you'd see this curve, this very clear curve. Now, in a much higher intensity- But the amplitudes aren't as big.
The amplitudes aren't as big, exactly. In a much higher intensity, higher volume, even lower intensity, it's easier to do two, three hours of it in heat.
That's a much bigger stress. You'd see the same curve, but it would play out over a much longer timescale because it would take much longer for the body to restore back to where it was and then to get everything where you started with from an HRV standpoint.
So we'd see a much bigger depression, a much lower drop, and then we'd see a much longer timescale for it to come back up to normal. And then we might see it come up above normal for some period and then restore.
But I'll say there's a big difference in the individual as well. People with higher HRV and people that are more fit, they're more likely to see this increase above baseline.
Somebody who has less autonomic range, they can't quite turn that peristeme thick dial up as much. They might never get up above baseline.
They might just kind of spend time getting back to that baseline HRV and you never really see the peak above baseline and then the restored afterwards. So it's an individual thing based on fitness, but we should generally see suppression of HRV, an increase of HRV, and then kind of a back to normal HRV.
And it's that

process. Now, the tricky thing comes is we have so many other things that influence it.
Alcohol

influences it. Mental stress influences it.
Sleep influences it. So it's overlapping influences that

will get to where you're seeing, but that's the core thing of our body response to stress by dropping HRV and then by recovering HRV and then by coming back to whatever that normal range is. Yeah.
And that's why, again, I think it's not intuitive enough to just look at the HRV that given day. You can't just say my HRV was X today and there's a one-to-one map between what my HRV is on a given day and what my training output should be that day, because you need to know the first derivative, the second derivative, and frankly, even the arc that it's on.
It's an all-cause metric that's not just looking at one input, it's looking at everything. And so interpreting that output is not always the easiest thing in the world.
And again, if you kind of look at this like, oh, up is always one thing and down is always one thing. It's a little more nuanced than that because it's this responsiveness of, okay, it's going to drop after pure stress, then it's going to come back up.
It might come up way above baseline and then kind of drop back down to normal. This curve is not always the most intuitive thing to understand.
And that's part of the challenge, I think, with people just kind of looking at it and say, oh, it's this, I'm going to go do that. Yeah.
I mean, it's certainly not intuitive to me, which is why I annoy the hell out of you and pepper you with all these questions. I want to change gears to talk about something I've alluded to a couple of times in the past, which is a phenomenon that we see in patients taking this new class of drug.
I mean, it's not really a new class of drug. It's been around for a decade, but a class of drug that has gained a lot of popularity in the past probably two to three years, which is the GLP-1 agonists and the dual agonists with GIP as well.
And again, we don't have an enormous and overwhelming body of evidence on this. We don't have that many patients in our practice and we frankly don't have that many that take it.
But certainly over the past three years, have to think we've seen two dozen patients on these drugs. And again, in all cases, we have overnight information on heart rate and heart rate variability.
The unambiguous sign that we see is that resting heart rate is going up and it's going up an average of 10 beats per minute with a range of about eight to 12. And this is unmistakable.
It's not subtle. And when they come off the drug, usually within a month, it goes back to normal for patients who do indeed go off the drug.
We're also seeing a compression of heart rate variability. So we see heart rate variability come down, although that's less predictive.
But I now realize we're kind of using the standard, we're not using like a

Morpheus, we're using kind of the aura ring or whatever. And maybe those data just aren't as

accurate. My first question for you is, if there's something going on in a drug that is predictably

driving heart rate up, would you expect it is also driving heart rate variability down? Do those tend

to move in that direction? Generally speaking, yeah. Generally speaking, you'd see that.
Now,

just as you mentioned that, my thought would be it's a strong appetite suppressant. Correct.
The vagus is very tied to appetite. So if you think about this, if we were to turn up that sympathetic dial, our hunger gets turned down.
We don't really want to be hungry while we're in the middle of some stressor, right? But after that period of stressor is over, theoretically, we've burned energy, we need to restore and eat. And so the vagus is very connected to the gut and to hunger centers, and it feeds up into the medulla and it's controlled hypothalamus.
There's a very strong vagal relationship to hunger and a desire to eat. So I almost wonder if suppressing the vagus and decreasing HIV, increasing heart rate is a byproduct of how this is inhibiting appetite.
That would make sense. And so it's an interesting question because it then leads to another question, which is if I told you that I'm going to change you in a way that your heart rate is 10 beats higher and your HRV is 10 milliseconds lower, you would say, well, whatever you did was negative.
Sure. There's a cost to that, right? Do we think that that could be the case here? I mean, again, we're really wildly speculating.
You know, I get asked all the time, Peter, are these drugs safe? Are these drugs good? What do you think of them? And I'm always sort of the same thing, which is look, clearly for some people, whatever unknown exists around these drugs is worth it. If an individual goes from being 250 pounds to 200 pounds and having a hemoglobin A1c of 7% to 5.5%, that is so positive for them that I think it justifies whatever unknown exists around these drugs if there's no other way they're going to achieve that benefit.
But I'm really more interested in these marginal cases of people who don't have diabetes and want to lose 20 pounds, which by the way, might not really matter in their overall health. It's cosmetic.
And are they taking too big a risk? That's kind of the question I'm interested in. And that's why I keep coming back to if if it raises your heart rate that much and lowers your heart rate variability, are we picking up a signal that is just a niche representation of appetite suppression via the vagus nerve? Or is it actually playing a role in the parasympathetic sympathetic dials? I would imagine it's got to be, I mean, to move it that large, 10 beats is a fairly significant amount.
I can't imagine that's not having an actual effect on our ability to regulate ourselves effectively. We're probably in a more sympathetic state all the time, which is going to have a cost.
Now, if it's a few weeks or a month, maybe that cost is relatively small. I don't know.
But if it's weeks or months, they're living on this drug, I would suspect there's a real cost to that. And to your point, if it's the benefit is they lose a bunch of weight and all their blood markers improve and we see health outcomes, maybe it's certainly worth that cost.
But maybe somebody, like you said, who cosmetically wants to lose weight and they have an easier time on the drug doing that, is that a net benefit? I mean, it's hard to say because we don't have long-term studies on those drugs, but I would just kind of say in general that, yeah, if we see these noticeable decreases in HRV and these very noticeable increases in heart rate, that's a real sign that the body is, that autonomic nervous system is being adjusted in an artificial way. And that probably is not a good thing in the long run, specifically if it's for a long time.
Yeah. I don't know where the companies are at in terms of their post-surveillance, meaning post-marketing surveillance studies, and if this is a metric that they're tracking or interested in.
But again, given the popularity of these drugs, there's no shortage of opportunities to measure these things. Yeah.
It'd be interesting to see. Also, I'd be curious to see what happens when they come off.
Do we see a big rebound? Does their heart rate stay suppressed? How does it change? Our sample size is so small that I want to be very careful and note that everything I'm saying is it could be nothing. It could be that it's just a very small N and 25 people is not enough.
But the thing is, in the 25 people, I've never seen an exception. When you don't need statistics to measure things, you kind of need to pay a little closer attention to them.
It's pretty hard to modulate appetite that significantly without suppressing the vagus to some extent. Yeah.
It's so close to connect. But we do see everything come back to normal when people are off the drug.
And I'm trying to remember, it's been a while since I've looked. I feel like it's within a month, maybe even less.
It might be within two weeks. Everything is going to.
It's very long on those. So it would probably just take a few weeks to clear out.
And I don't think I have enough insight to contrast the two most popular drugs, semaglutide and terzepatide. But again, I don't think these drugs are going anywhere.
And I would love to better understand this. My guess is there are a number of people on these drugs that might not be aware of this because either they're just not tracking it or they are but they haven't noticed it some patients will say this after a few months and i realized they kind of forgot when i told them this in the first place but anyway wondering if you had seen anything about that or heard anything about it adhd medications for example you see a very suppressed hiv and a very elevated sympathetic heart rate you see in several of things like that, any sort of strong stimulants, obviously those are not stimulants, but people who live on caffeine and Red Bull and are constantly shoving coffee, like to constantly turn that sympathetic dial up is to me a kind of sign that the sympathetic system isn't working the way that it should by itself, probably because you've overstimulated to begin with through stress and the lack of ability to turn that off.
And we see people reach for stimulants and artificial ways of turning that sympathetic dial up once their body's not doing it the way that it should. And so we see people kind of self-medicate with stimulants to get that sympathetic response when if they had been able to manage stress more effectively, they probably would have a normal functioning sympathetic system that wouldn't need that artificial stimulus to turn it up.
Let's take a step back and now just talk about where you think HRV belongs in the hierarchy of health metrics. We've talked about so many different types of health metrics, and we've talked about how output metrics tend to be preferable.
We can sort of think of them as functional metrics. I like an oral glucose tolerance test more than a hemoglobin A1C.
One is kind of functional. It actually is a test.
It watches how you do something. VO2 max, strength, those are more functional tests than maybe resting heart rate or muscle mass.
Muscle mass is great. It's predictive as is resting heart rate.
But when you actually put the workout, HRV is obviously a readout state. Where do you think on the dashboard of health, longevity, where do you place it? I think it's important to monitor as you're going along, but I would say if all your other metrics are telling you you're healthy and you're going the right direction, nine times out of 10, we'd tell you the same thing.
The point where I would be more aware of it is where it's very low and you don't have a reason for that. You'd want to figure that out.
We've had people have arrhythmias they had no idea about and they go to the doctor and they have some serious heart condition that they need to be aware of. But I would just say long-term, it should line up with VO2.
It should line up with your metabolic market. It should line up with all of this stuff.
It's easier to track because we can measure it on a daily basis. I think that's probably the advantage I would say it has is you're not getting a VO2 max test every day, obviously, or every week, every month.
You're not doing lactate tests. You're not doing these markers that are more output-based that are really important frequently enough to get feedback of whether or not you're going the right direction.
So I think we can look at HRV in a more granular daily basis, just kind of say, am I going the right direction? And that's probably more of a utility than a great predictor of something. And we can look at those daily changes to help us make more informed decisions.
We can't do that with VO2 max or with more invasive tests. So it's a more narrow data point, but it gives us something we can use more actionably than these longer-term tests that I think are better actual measures of outcome.
And if we see our HIV trending down significantly, that is a warning sign. We're doing something wrong.
Our body is not adapting the way that it should be, and we need to make adjustments, whether it's training or lifestyle. So I think it's used differently.
We use VO2, and we use those sorts of output measures as, are we going the right direction? And we have some prognostic value specifically from them. We use HIV to say, are we more likely to be making improvements in the short term or are we heading the wrong direction where if we keep doing that for a long period of time, we're going to either see the benefit or the cost depending on which direction we're going.
So I think they're different. Is there a number, Joel, on the log normal transformation you're doing on the RMSSD, a number below which, if it's consistently there, I would want to inquire more? 50s, 40s.
I mean, those are pretty low numbers for a Morpheus user. Again, just for folks listening, that's not the RMSSD number.
The RMSSD number might be far, far lower than that. Yeah, exactly.
Yeah. So you really do have to be specific of what we're talking about the systems.
This is a, and a one, but I was at a guy, there was a guy named Mel Siff who you probably aren't familiar with, but he was a very well-known sports scientist. He wrote a book called super train.
I was at his house with the original HRV system I was using and I had all the metrics and his armist, he was like five and he just looked really bad. Then he had a heart attack.
And I said, Mel, this looks really concerning. He was, you know, he kind of brushed it off and he died of a heart attack a few months later.
And so, you know, if you're really seeing this super low arm SSD or Morpheus numbers, like it's definitely an indication that that autonomic nervous system is not responding well to the world around it. If it's really, really low, there could be a legitimate medical concern that's driving that.
So if your Morpheus 40s, 30s, and you're just not getting up, it's probably worth looking into, and it's something to definitely be concerned about. And do you see the opposite, where really high numbers or a sudden change from low to high can indicate an arrhythmia or something like that? Yeah, absolutely.
You definitely do see these weird numbers come out that could be arrhythmia, that could be medication, that could be who knows. You see some of these things jump around from anomalies that you just kind of like, that's an artifact.
I don't know what happened. And then sometimes you do see a medication or you see weird stuff with COVID and you definitely see some weird stuff in the data that you want to be aware of that you probably wouldn't pick up otherwise.
I would say HIV is more of a leading indicator and kind of how you feel and some of those symptoms can come days later. So you'll oftentimes pick up something that looks weird and then two days later you get a cold or you get flu or you get some sort of thing that explained it.
Good, good. Joel, this is awesome.
I feel like I know much more about this now than even after I did the AMA a couple of years ago and I learned a lot to sort of prepare for that. So appreciate it.
And again, I apologize because on some level, this for some of the listeners probably sounds like a bit of a Morpheus commercial at times, but obviously I have no affiliation with Morpheus at all, but I point to it because again, I'm a big consumer of data. I test every device out there extensively and I view it as the stickiest device I've ever found for this use case.
And so I do hope that people check it out. I think I just bought it online.
You buy it direct to consumer, right? I don't think you buy it on Amazon or whatever. So I would encourage people to, if they want to take this to another level, that they should check out Morpheus.
I appreciate the work you're doing, Joel. The curiosity and inquisition with

which you bring to this is fantastic. I benefit from it greatly.
And those are my patients who

use it also as well. So thank you for both all the work you're doing and obviously coming here

to talk about it. I appreciate being on here and being able to speak to your audience.
I think the

biggest thing I've learned after 20 plus user coaching is we're all different. And as much as

it may be easy or attractive to say, oh, this is what somebody else is doing. Let me just try that.

Let me just try that. Let me just do the same thing.
If you can spend time just copycatting someone else's workout and really dig into your own physiology, how you respond to training, how you respond to diet, how you respond to different food intakes, really learn how your physiology works, you will reap the reward of that in the long run. I think that's where tools like HRV and sleep monitors, they build awareness.
And whether you're using Morpheus or URA or whatever else, using that data to really be your own coach and really understand your own physiology and your own biology, that's the ultimate way to get better results and have the health outcomes you're looking for. So I appreciate the opportunity to talk about that.
Thanks, Joel. Thank you.
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