A Deep Dive Into HRV: The Myths & Truths of Heart Rate Variability Testing

Hey, it's Ben Greenfield here, and I hope you're ready to strap on your propeller hat, because today's podcast actually involves a pretty deep dive into something called heart rate variability. And I gotta be honest with you, I was a little bit afraid during about the first 20 minutes of this episode that this was just going to be extremely theoretical blue sky stuff. But especially towards the end of the episode, we got into some really interesting discussions about everything from how supplements and medications affect HRV to do it yourself, ECG monitoring. That's literally the same quality as you can get at a hospital to the concept of using something called metabolic breathing ladders. And it really turned into to a quite interesting, yet still very nerdy discussion. So, a couple of things. First of all, all of the show notes for this episode, because there's plenty of links to research articles, et cetera, are over@BenGreenfieldFitness.com AdvancedHRV and then second, I honestly do not expect you to understand much of this episode unless you have a basic understanding of heart rate variability and HRV going into listening to this. So if you don't have an understanding of HRV or heart rate variability, don't start here. There are other podcasts. Over at BenGreenfieldFitness.com, i'm going to link to the best three podcasts and the best two articles that I've ever had appear over on the website that you can use as a way to really learn everything that you need to know about HRV prior to taking this deep dive into hrv. So I'll put links to all of that stuff along with all of the shownotes for this episode over at BenGreenfieldFitness.com AdvancedHRV that's BenGreenfieldFitness.com advancedHRV and since it sounds like I have a burglar attacking my house with the amount of dogs barking in the background, I should probably go make sure that everything's okay and leave you to enjoy this episode. In this episode of the Ben Greenfield.

Fitness Podcast, there's an awful lot of people using hiv. There's still a really big knowledge gap between the center of the stuff that we know about how it works and what people are using it to do. Meditation, for instance. If you're the kind of person who is continually tense, if it's something that could be of great use to you individually, you may find a tremendous difference. But is that because specifically of the meditation or the outcome of the meditation? With the right magnification, amplification you can just get a webcam and turn the webcam on, then you can turn that into heart rate over time. For your recovery. When your heart rate goes too high, I would suggest breathing through your nose very slowly with your mouth closed, which is extremely tough to do.

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Hey folks, My guest today, Dr. James Heathers, is a pretty interesting dude. So on a professional level he's actually a PhD and an endeavor research fellow in electrocardiology at Poznan University of Medical Science where he researches stuff like heart rate and heart rate variability. And then on another level he actually has a pretty cool blog over@jamesheathers.com and at that blog he writes about health science, medicine, bioethics and he has articles on things like medical sensors embedded in tattoos and how drinking alcohol affects sleep quality and how peptides are used for doping by professional athletes and a lot of other really kind of like interesting fringe cutting edge topics. So today I thought it would be really interesting to get Dr. Heather's on to talk about heart rate variability because he actually is one of the leading thinkers when it comes to heart rate variability and hrv. He recently had a very interesting interview in one of the research digests that I subscribed to called the Examine Research Digest. And some of the stuff that he talked about in there was really cutting edge and things we haven't discussed on this show before. When it comes to HRV and, and heart rate variability, which as I've mentioned on other podcasts is one of really the only self quantification things that I do just about every day. So it's near and dear to my heart and I think it's near and dear to James heart too. So James, thanks for coming on the show.

You are most welcome.

Well, you were an experimental psychologist if I'm not mistaken. What happened? How did you go from being an experimental psychologist to being involved in something like HRV research?

That's actually an extremely good question. The short answer is that psychologists use HIV all the time and I had started to become interested in the work and it was a simple matter of pushing back against the way that I saw people in behavioral research using HRV to do experiments. I wasn't particularly satisfied with the outcomes that people got from experiments. I wanted to know what it actually meant when they said the things that they were saying. So I started looking more closely at the methodology of HRV and then eventually the signal analysis and cardiac environment sort of area where it's actually from, and very occasionally the cellular basis as well. So it was a path that started with wanting to know more how. Wanting to know more about how you could use it for macro level human research and then just pushing back against it really, really hard for four or five years. And now I work in electrocardiology proper.

I didn't know that HRV was actually used in psychology. What's an example of a way that it would have been used in psychology that would have turned your head back in the day when you were doing experimental psychology?

One of the first papers I saw was using it as an outcome for a placebo measure. When psychologists use placebos, they're not the same as the medical science placebo where you give someone the actual pill. You usually test a psychological placebo as trying to make the placebo effect rather than trying to control for it. So you give someone something inactive and you say that's a stimulant or that's a depressant or that's going to make you upset. Research that was doing that was using HIV to quantify the outcome of those experiments. But it's very widely used through, oh, attention and emotion. There's an awful lot of studies on different psychopathologies. Anxiety patients in particular have really bad HIV and they have even worse hiv. When it comes to stress challenges, some of my favorite research is on. Well, right now I should say some of my favorite research is on the cessation of attention. What immediately happens when you stress someone for a little while and then you stop? What happens in the period immediately after that? Which is a good question that hasn't been properly answered yet because obviously like sports science stuff, macro level changes to people and to the autonomic nervous system of people are relevant to how they behave. You can imagine being stressed out by something you don't have to move around. It can be something that's an entirely psychological phenomenon and you can measure stuff like that with hrv. Whether or not that research is any good is another question completely.

That's really interesting because most of what I've seen when it comes to HRV has not really been in experimental psychology or psychological research or research into anxiety and stress and depression. Probably because I'm in more in exercise physiology and working as a fitness coach. And so most of what I see is from, you know, European soccer teams and the NFL using things like heart rate variability. So that's interesting that it was such a staple of something like psychological research prior to kind of taking the fitness world by storm, which it seems like it's doing now. So in your opinion, from what you've studied so far in terms of hrv, what are some of the more interesting uses of it that you think either fly under the radar or that people kind of aren't aware of when it comes to hrv? Or some of some of the more intriguing ways that HRV is being used, whether in both research or kind of in the field?

I'm quite happy with the current attention that HRV is getting in athletic monitoring because it's pretty good. So we'll put that to one side. There's two in particular that I think are going to be a lot bigger in the next five years because they're very definitely got relationships between HRV that you can legitimately actually measure and behavioral sorts of outcomes. And those two things are as adjuncts to computer games and to immersive environments. And the other is as an adjunct to an attentional state which related to what people who aren't scientists generally call flow. At least that's the easiest way I've got of conceptualizing them. The reason for both of these things is relatively similar. It's the fact that we are pretty sure we have actually some of the earliest research in HIV in the 70s was on this. But it's one of those things that's been curiously under researched. Even though it's really very obvious when you are paying attention to something and you are continually on task, so you are watching something that you have to respond to and it's not cognitively challenging. It's a very easy thing to do. So an example would be a task where there's a dot that comes up on the screen and all you have to do is respond to it every now and then, every couple of seconds. So you have to pay continuous attention. But it's not cognitively difficult. Tasks like that seem to have their own concomitant HIV state that's characterized by very regular breathing and HIV that's constrained to that breathing and the changes, a change in the blood pressure fluctuations that are buffered into the heart rate and that goes equally for time on task, sorts of things. So writing, paying attention to something, monitoring tasks, and computer games as well. The reason that computer games are particularly interesting is because we're now starting to get the collective normalization of virtual and ostensibly 2, 5D and 3D environments. So I've played around with this a little. It's very easy to make an immersive task where you naturally pay attention to it more than actually doing something on a computer.

Interesting.

And there are monitoring methods that no one's tried yet of sewing the two things together. And people, obviously there's research to these sorts of things. Human factors research largely covers the attentional monitoring sorts of experiments. And there's a separate human computer interface stream of research that covers the computer game stuff, but none of its particular advanced. It's interesting as well. This happens with sports science as well, and exercise physiology and sports management, fatigue management, etc. There's an awful lot of people using HRV and none of them do formal physiology or electrocardiology stuff. There's still a really big knowledge gap between the center of the stuff that we know about how it works and what people are using it to do.

What do you mean when you say, like formal physiology or electrocardiology being used in conjunction with hrv? What would be an example of that?

Something that I would find particularly interesting about people who deal essentially with the research topic of how HRV works and what it is, rather than using it to compare to a separate outcome. So if you have, like you said before, research out of Europe, there's a bunch of people, they've got a soccer team, I can call it that here. I don't have to say football. They've got a soccer team. They're using it to. Using HIV to manage fatigue over time, and they're taking measurements of it. That's making a series of assumptions about what HRV does, what it can represent, etc. It's being operationalized as this is a measurement of fatigue. The sort of stuff that I do is usually concerned with what is hrv, how can we measure it, what do we do? So we do things like what's called graded tilt or orthostatic tilt, where you have someone who's lying down on a table that goes all the way from completely flat to vertical. And you look at the different responses between blood pressure and respiration and the heart rate through different environments that you change by changing essentially the. The direction of the gravitational axis of the person. So we're pushing them essentially in the completely same position from lying down to standing up. And we're looking at the differences in a variety of contexts between the different measurements and the different angles. No other reason than the fact that we want to know more about how HIV works. Now, there's plenty of people doing research on this stuff, a lot of whom I've met, and they're all. It's a very good environment. It's quite a positive research environment. It's a nice one where you write emails to people and they write back. And people have a great deal of knowledge, usually about the specifics of how cardiological factors work and the specifics of how the signal analytical factors work. So how should we understand a series of heartbeats over time and turn that into information? So that's a very long winded way of me saying that there's two research traditions when it comes to this stuff and people who do applied research a lot of the time shut down a bit when it comes to the finer details of what they do. That's perfectly normal and it happens in all sorts of research areas. But it does mean that there can be gaps.

And where are you doing most of your research? Where is this? Poznan University.

I'm just about to go there. That's. I had to do an updated bio. That's why I was at the consulate today getting things sorted. Poznan is in western Poland and the Australian government were kind enough to give me a sack of cash to go to Poznan and work at the hospital with some really excellent electrocardiologists whose work I've been reading for ages. And I'm specifically working on the problem of the fact that when we have high frequency heart rate variability, it is the variability in the heart that's modulated by respiration by breathing. Now, we measure that generally by doing spectral analysis by breaking it down into a series of sine waves and saying there's information present at certain frequencies, like the frequency of breathing. Obviously the interesting thing about it is they're not actually sine waves. The inspiration breathing in and expiration breathing out have different shaped responses. So your actual HRV is not a wave, it's actually a sort of a hunchbacked wave. And the hunchbacked wave, if anyone wants to look this up. But I sincerely hope that there isn't anyone out there who's. Who's so interested enough in it that they really want to try this. But if you want to look for it, it's called heart rate symmetry.

Sorry, I said you'd be surprised.

Oh, well, that's. It's all perfectly okay.

A lot of propeller hats listening in.

Nice to have more people in the field. Heart rate asymmetry. We're looking at some different factors in heart rate asymmetry and it probably has Something to do with how the response in the pressure receptors in the lung are actually modulated over time. I'm also particularly interested in the fact that you don't. In any normal ECG that you get, when you're taking a measurement of the electrical activity of the heart over time, you actually have a breathing signal that's hidden in that, because the shape of the ECG changes with the respiratory cycle, because the direction of the current on the heart is moving in the chest. I'm not sure I can explain any simpler than that because I haven't done the research yet and I don't quite know what I'm talking about. But we're looking at ways of getting the respiration signal out of the heart rate signal, which is something that's been tried a few different times, but I've got my own methods for doing it and we're going to see if they're any good trying them out in a proper laboratory.

So when you're getting the breathing signal out of the heart rate variability signal, all that you're doing is eliminating the potential influence of any type of special breathing protocol that someone might be doing and the effect of that on their parasympathetic nervous system.

We wouldn't necessarily be trying to pull it out in this particular context. If we're trying to measure HIV in the normal way, I'd be trying to match up the respiratory signal that's there, the amount of HIV that it actually gives us. This becomes conceptually quite sticky because most of the time when we're talking about high frequency hrv, it's because it's an approximation of the respiratory modulated heart rate in the first place. But the problem becomes a problem of language. There is that people start to refer to them as the same thing, even though they're not the same thing. So sometimes you see it called respiratory sinus arrhythmia, which is technically what it is, respiratory as in breathing, sinus as in sinus node, the bit on the top of the heart that makes the cardiac cycle start, and arrhythmia as being not particularly rhythmic over time, as having a fluctuation, accelerations and decelerations, et cetera. I don't know if that's a very good answer, Ben. Yeah, yeah, I very rarely explain this out loud. It's an interesting experience.

So what you're basically saying is that when it comes to the relationship between someone's respiration and their heartbeat, that it's not like a simple linear relationship, not at all. And so the heart is going to decelerate and accelerate separately from breathing. But a lot of the current heart rate variability apps or algorithms or research make the assumption that breathing and HRV are a little bit more linearly related.

Here we get into an issue of measurement. I don't have a problem with the way that most applications, most general applications of hiv, especially for athletic training, are fine. And the reason for that is because we're talking about two different types of measurement fidelity. The kind of stuff that I normally deal with is fine grained and a little bit. It doesn't necessarily have practical significance. But here's the nice thing. Really heavy duty deadlift workouts and half marathons and cluster sets of chin ups have an absolutely massive effect on your body. As you're probably well aware, these things really slam you. And when you're actually properly over trained in the short term, you can see a very obvious difference in HIV that's much bigger than the measurement questions that we have to deal with when we're talking about the fine grained details. If you slam yourself, it doesn't matter whether or not the measurement is absolutely perfect. It just needs to be good enough. You need to be able to say, I'm in less good condition today than I was yesterday. That's your important piece of information.

Gotcha. Okay, I want to kind of use that as a segue into asking about what a lot of these things in the current self quantification industry are actually measuring. Because there are claims out there with all these different apps and HRV tools that they can measure things like the strength of your sympathetic versus your parasympathetic nervous system, or your approximate blood lactic acid levels, or your readiness or lack thereof to train. So when it comes to what the folks in the self quantification industry who are putting out all these apps and stuff for quantifying heart rate variability, like does HRV actually measure all of these things or is that like blue sky thinking in your opinion?

There's two answers to that. The first answer is the only thing that I'm really comfortable saying that HIV definitely does is it's a good measurement of the modulation of cardiac parasympathetic. So if you are entirely at rest and entirely calm, you should be seeing a certain sort of signal. And when you're not, in the absence of that, you should be seeing another signal. The interesting part there is that this question doesn't come up in research at all and it comes up in device design and wearable computing and app stuff for the simple reason that it's easy to measure heart rate stuff. But your three examples there were parasympathetic to sympathetic balance, Right, Right.

That and a couple of those I've seen. Yeah. Blood lactate and then, like, readiness to train. Right. Like green light versus yellow light versus red light. Take an easy day.

I understand the third one, but my answer to the first two is substantially less positive. The whole idea of parasympathetic to sympathetic outflow is built on a piece of theory from the early 90s by a group of Italian cardiologists who I had a fight with a couple of years ago because they're wrong and they never really admitted it publicly. It's. It's something that's been noted by people who are much more senior researchers than me. The whole idea of using spectral HIV to measure autonomic balance is just. It is just not supportable anymore. There's no particularly good evidence for it, and it doesn't work very well. Blood lactate. I'm very surprised that anyone would try that for the simple reason that we've already got very good ways of measuring blood lactate. You take a finger prick and you use a blood lactate method monitor that have been portable for the last 10 to 15 years. I have one.

Yeah, but you still have to bleed, right?

Yes, but you don't have to bleed very much.

But there's no research that you're aware of that draws a direct corollary between lactic acid levels and hrv.

I think that's a very long boater draw. I don't think I'm turning over ways in my head that that might actually be possible. The two alternatives. That is decidedly ambitious. Or there's someone out there who knows a lot more than me about what they're doing. I don't think blood lactate is. I don't think that's feasible from an HIV measurement. And blood lactate can be a bit finicky.

Yeah. I think it was a study in the Journal of Strength Conditioning Research where they claimed that HRV indexes were associated with blood lactate levels. And I don't have the exact research study on hand, but that's a. It's a journal that I read, and I remember coming across that and thought it was kind of interesting and just curious what you thought about the relationship between, like, HRV and blood lactate. But ultimately, like, the bigger question here, James, is would you, as a lot of people are doing, based on what you know about hrv, like, wake up in the morning and do an HRV measurement? And use that measurement to give you input about the type of activities that you should or should not be engaged in that day. Specifically regarding like hard training versus easy training or your potential for being in an overreached or an overtrained state.

Oh, as a model for self monitoring, if I was training harder than I was right now, which is not particularly hard. Yes. The idea that at any point in time you can put a good finger on exactly how hard should I perform structured physical activity today is not. I don't know, I'm 5050 on that. But that's a separate question too. Have I woken up really seriously insufficiently recovered from what I've done the day before? I think it's much more important that you pick up signals that you're absolutely in the can than how should I go sort of medium versus extremely hard today? Because there's plenty of research on this and I've seen it in myself. It's particularly straightforward. If you are under slept and over trained and you wake up, you will see a good solid difference in your waking hrv.

Interesting. So is a high HRV always a good thing? Because you see a lot of people with, with HRV levels of like 95, 100, oftentimes even higher. In your opinion, is that exclusively good across the board, 95 or 100? What you mean for most of the current HRV apps, Right. They're kicking out a score that's based off of a smoothing of the. I believe it's the root mean squared number where they're, they're creating like a, like a scale of 0 to 100 for HRV. And most of the time what the prevailing thought is is that the higher the hrv, the better, the more prepared you are to train or the lower amount of stress that you're under.

Okay, I just wanted to know what the number was. Rmssd, incidentally, is pretty good. Really. It probably has the best properties of being easy to calculate versus actually being meaningful. I quite like that as a measurement and I'm glad that applications in general are using it because it's the easiest way of solving a complicated problem. But to answer your question, the vast majority of the time when people are healthy, it's a good thing. There are plenty of situations where it isn't, but you're very unlikely to encounter them on a normal athletic training basis. So if you are seriously properly over trained and you. Have you heard of Addisonic overtraining? They used to call it that because it has the same presentation as Addison's disease.

Yeah, like really Getting near to complete adrenal fatigue.

Yeah, yeah. Basically your whole endocrine system is shut down. It's pretty much not there for you. Yeah, you'll have very low waking heart rate and a reasonable, reasonably high waking hiv. It doesn't mean you're in good condition at all, but I think that's extremely uncommon. There's lots of people claiming to be overtrained that really aren't. You're far more likely to have less than more.

So if you had a really, really high HRV consistently on a daily basis and you weren't feeling good, it may be beneficial to go out and do something like an adrenal stress index and look at your, your cortisol and your DHEA levels, that type of thing.

Yeah, I would, I would definitely see an endocrinologist. If you train really, really hard for very long periods of time and you skip sleep, I don't think you really see over training like that in people who aren't poorly monitored, professional athletes or people who have physical jobs and training on top of that, or some other concomitant sort of condition. It's pretty uncommon, but it does, it does happen. It's probably more common in heavy duty endurance sports as well than it is in.

Yeah, yeah, but it would need to be accompanied by symptoms like just having a consistently high HRV and having no other symptoms. Typically. That doesn't indicate that you have something like Addison's or adrenal fatigue or something like that. No.

Look, if you have something like that, you will have many, many other fine symptoms. It won't simply be the fact that you have particularly high HIV in isolation.

Now, what about supplements? There are some supplements that are actually touted as being things that can increase hrv. In your opinion, when it comes to things like supplements or medications, is there any research out there in terms of what may or may not increase or affect hrv?

That question confuses hrv. The thing that we measure with the outcome of why you'd want to take the supplement in the first place. The idea of something that can increase your HRV because HRV is just a good thing isn't really tenable. The idea of something that means that you recover better from what you're doing, that could increase hiv. I might be willing to accept that that could work.

Right, okay. So basically indirectly. Well, let me give you some context too. Like the reason I ask, for example, is as I mentioned earlier, I monitor HRV every day and I have found extreme suppression of HRV by like, you know, and typically I'm around like 90, 95 and I've measured it in the 60s to the 70s after using like, like a Benadryl or, or Nyquil type of supplement. Right. Like an antihistamine. I've found that that significantly decreases hrv and I was just curious if you had, you know, thoughts about, about chemical substances that, that can affect HRV like that and how something like that could actually.

That is interesting. I don't actually know. I'm Australian, in case anyone has not managed to pick that up. Does Nyquil contain pseudoephedrine by any chance?

But why do you ask? And by the way, yes, it does contain pseudoephedrine.

There you go. Well, pseudoephedrine is. It's a sympathomimetic.

So it would increase your sympathetic nervous system drive and therefore decrease hrv.

Yeah. Interestingly enough, the stuff that. Because people make amphetamines out of it traditionally, so they've pulled it off the market in a lot of places and replaced it with something else called phenylephrine. Phenylephrine, interestingly enough, will transiently increase your hrv. Completely different method of action thing. But that's. Yeah, look, that's simply related to. You've. This is. This, this is, this is quite difficult to explain. Let me, let me, let me try and get this right.

All right?

You're measuring your HIV in the first instance because you are or are not recovered from what you're doing. You're stressed or you're not, your body is in the tank or it isn't when you take different sorts of drugs directly interfering with the process of how the HIV is produced as an outcome of the system that it's from. So increasing or decreasing your HIV doesn't really mean anything in terms of what you're using the HIV to originally measure. Does that make sense?

It does make sense. It sounds to me like what you're saying is, for example, when we look at something like, say, meditation and the effect that that has on hrv, all that we know once we've meditated is that that in like an acute state is affecting HRV while you're measuring hrv. And it doesn't necessarily mean that it's having like a, like a lasting effect on your nervous system per se.

Yeah, yeah. The whole idea of something having a direct effect on your nervous system, these concepts get smashed together all the time and people aren't particularly well concerned whether or not they make any sense. Meditation, for instance, if you're the kind of person who is continually Tense and not particularly mindful. If it's something that could be of great use to you individually, you may find a tremendous difference in your hrb. But is that because specifically of the meditation or the outcome of the meditation, which is interfering with your ability to make yourself anxious?

Yeah, I hear you. And for example, I've said this before, that if you wake up and you take your morning heart rate variability and you notice that it's low and right there, while you're lying there, you figure out that if you do something like meditation or box breathing or alternate nostril breathing or just relaxation, that you can increase your hrv. All it shows is that you're good at increasing your HRV in that specific situation when you're lying in bed, quantifying it, but it doesn't necessarily mean that it's affecting your stress levels the rest of the day.

Yes.

However, what I would say is that, and this is how I would use something like this, James, would be if I am able to see that something like alternate nostril breathing. Breathing in through my right nose, out through my left nose, and then in through my left nose and out through my right. I only have one nose in through my left nostril and out through my right nostril. If I find that affects my HRV acutely while I'm measuring HRV and that it's decreasing stress, then I know that even when I'm not measuring hrv, like at a later point during the day, right, when the. When the lion is jumping out from the email inbox in my computer or my children are annoying me, I can engage in that same practice. And I know that it's probably having an acute effect on my nervous system. Right? We could safely say that. Right?

Yeah, you can. The problem with the idea of breathing to increase HIV in general is that when you breathe slowly, there's an awful lot of things that make you breathe more slowly. Meditation is just one of them. When you breathe more slowly than usual, you don't have normal respiratory sinus arrhythmia. If you remember from before the normal modulation of the heart rate by breathing, when you slow it down, you get much, much more hiv. I mean, lots, lots more. If you look at the two spectrograms side by side of someone breathing normally and relatively quickly and someone breathing slowly, there's absolutely no comparison whatsoever. That is simply because you are lining up your normal ability to buffer changes in your blood pressure that happen normally via what's called, or the baroreflex, which is the blood Pressure management system of the whole body. You're aligning, your respiratory changes up with your blood pressure changes. So the colossal amount of HRV that you get when you breathe slowly is what we call an epiphenomenon. It's something that happens because of something else basically in this scenario. And it doesn't really mean anything by itself. So if you've got perfectly heart, works perfectly normally, everything's perfectly okay, and then you slow your breathing down and you get a colossal amount of hiv. It doesn't mean that you're twice as healthy or twice as calm. It just means you're breathing slowly.

Yeah, yeah.

What it does on top of that, I mean, when it comes to acute stress management stuff, that's. You gave a very good example there. There's been a ton of research of people, people in different situations where they're saying, if you're particularly stressed at this point in time, if you can control your breathing at the point in time that you're actually stressed, is there going to be a relationship between you doing that and changing your autonomic environment coming through to your behavior? And a lot of the times the answer to that has been yes in a number of different contexts. But why that's the case is actually quite a thorny question. Is it the fact that you're making people aware of what's happening to them? Is it the fact that you're knocking off the cycle where you hyperventilate and you freak out and you start to feel upset and you're removing people's ability to react to their own internal cues? Or is it something more interesting where you're modulating your autonomic environment over time? Simple. They're not easy questions. There's lots and lots of stuff that's wrapped up in the answer to any individual question like this. Yeah, I don't mean to sound boring about it.

No, it makes sense. It sounds like, though, based on the research that you're planning on doing, that once we figure out a way to be able to separate something like the respiratory signal from the HRV signal, we'll never truly know how much of an effect something like breathing is having directly on the nervous system versus how much of an effect breathing is just having on the effect of a change in respiration on hrv. Right.

Well, you're right in the fact that being able to separate them gives you a lot more information. Obviously, right now we can measure respiration via other methods, but then we run into a completely different problem again. And that's the fact that Respiration is surprisingly irritating to monitor. You can either put a mask on someone which is not a particularly pleasant experience if you've ever worn one. You can put a mask on someone which changes their respiratory mechanics and makes them look weird and feel a bit silly, or you can have all these sort of half measures of looking at the size of their chest at any individual point in time, which is isn't the amount of air that's going into them at all. There are a lot of measurement issues that come crunching up against each other when we start looking at the details of these things. And that's specifically why we're looking for respiratory information straight out of the recorded cardiac cycle on an ECG is because it's a very useful thing to have.

Got it. What are you using when you measure HRV in your research? Because there's everything from the fingertip measurements to the Bluetooth enabled heart rate monitors that send a signal to the app, like in a research, in a clinical research setting, what is being used?

If it's a clinical research kind of setting, we use a laboratory ecg, which is all wonderfully accurate and expensive.

That's an electrocardiogram.

Yes, exactly. But I've used, actually I think there's a place for just about everything because my primary ECG that I was using through the end of my PhD, that's set up in the lab that we had at Sydney, it cost about the same as a compact car does in America. It's not a cheap piece of equipment, but there are lots of other things that are a lot cheaper and a lot simpler. And the problem that we have when we're talking about the differences between psychological constructs especially and HRV is the fact that both measurements are messy. HRV is a fairly messy measurement. And when you have something like a personality measure, you're trying to measure someone's neuroticism or their openness or how they react to new experiences. The measures that you take, you accept the fact that they're not very good. And when you have measures that are not very good, one of the best ways of addressing what you do is to have as many people as humanly possible in your system study, because your study runs the risk of being underpowered. It doesn't have enough people to make realistic, statistically meaningful decisions about what you're actually trying to measure. So if it's the case that I can use a fingertip smartphone mediated heart rate measurement, and I accept the fact that there's a couple of percent inaccuracy if I can get 20 times as many people. That's a better idea than using the lab equipment.

Right.

It's, it's a trade off between your access to the sample that you're using versus how many people you're going to get in the sample. So I'm, I've done a bunch of research using the, the finger clip from the athlete monitor. Do you know the athlete monitor?

Yeah, I'm familiar with the athlete.

Yeah. I've worked with Simon, the guy that owns the company and designed it, et cetera, and we made a research version of the app and I've got a few studies where with hundreds, thousands of people taking HIV measurements at the same time. Now you could never do that with a laboratory ecg. It's not the fact that it's impossible, it's the fact that I don't have half a million dollars to run the study.

Yeah. Now in your article that you were interviewed in for the Examine Research Digest, you did talk about a few new monitors or monitoring environments that are being developed, like some cool kind of cutting edge technologies for either analyzing HRV or portable electrocardiogram, stuff like that. Can you talk about a few of the ones that you're excited about or that you think the self quantification community will find really interesting?

Would it be silly if I asked you which one? Because stuff like that changes.

Well, some of the ones that I thought were interesting. So for example, there's one that can pull your heart rate straight out of a webcam picture.

Ah, yeah. That's actually a couple of years old. Now this is a bunch of genius. People at MIT realize that if you take the redshift off of video and you point it at someone's face, you can see their blood moving through the microvasculature in their skin. And what it means is that the normal measurement that we might get off a fingertip where we shine some light in and we get a reflection off the amount of blood that's inside and we use that to measure the heartbeat over time. You can do that straight out of a video.

Interesting.

So with the right magnification amplification, you can just get a webcam and turn the webcam on and then you can turn that into heart rate over time. Now it's probably not accurate in the way that I've played with it. It's probably not accurate enough to get good hrv.

That's kind of cool though. You can use your webcam as at least a way to measure that.

Well, it's a couple of years Old now people use their smartphone cameras to do exactly the same thing.

Oh yeah? Yeah. I guess if you could do it with a webcam, you could do it with a smartphone cam. Huh.

It's exactly the same principle, it's just a different way of getting it. You've got your finger right over the top of the camera and it's being illuminated by the light in the back of the smartphone. And the red shift that's changing as your pulse is propagating through your finger is the thing, it's going into the camera and it's turning it into the amount of red present basically. And that becomes the vasculature signal and it chops that into heartbeats. It's extremely clever. I wish I thought of it.

That's kind of cool. What about this thing called the Sim band? What is that?

Sim band.

It's like this thing from Samsung that's a platform for developing software applications, I believe, that are associated with hrv. Do you know what I'm talking about?

Yes, yes, absolutely, of course. Sorry. You had me there for a second. The Sim band is a developer kit that Samsung make. And instead of, if you're looking to do a biomedical wearable kind of build putting hardware stuff, and there's lots and lots of little companies that are trying to do that, it is basically a one size fits all measurement system for doing that. So you can, you can add different peripherals, you can add different measurements to the environment. It's basically a test bed or a test kit for doing all sorts of biometric measurements. And they're all, they're all knocked together. It is for people who are developing sensor technology from scratch. So you might have measures of PPG and then you've got a normal ecg so you've got an electrical thing and a blood volume sort of thing or a light thing, a skin conductance sort of thing. It's an environment for, it's an environment for the development of new senses.

Right, right. Yeah, I think that one's pretty cool too. And I'll put a link to this stuff in the show notes, by the way, if you go to BenGreenfieldFitness.com AdvancedHRV I've got a lot of show notes about some of the things that we're discussing. The last one I wanted to ask you about, James and I know we're coming up on time here so I want to respect your time, but there was also this, this research grade ECG machine that apparently you can buy for like a few hundred bucks. This. How's it pronounced the Bitalino?

Yes.

How's that work?

Lovely guys. A bunch of electrical engineers from Europe. Basically, it's simply the fact that your access to sensor tech stuff and PCBs and the general environment of how you get hardware built to measure physical things is now accessible enough that there's a little open source company that will make you research grade.

Everything.

There's an ECG and an EMG that measures muscle activity and a GSR and an accelerometer, et cetera, et cetera. And you have all of the these different sensor environments and they come in a little kit that you can break apart and you can stick together yourself so you don't have to do any of the hardware development yourself. If I'd had one of these at the start of my PhD, I feel like I would have got a lot more done.

That sounds like something cool to just have around your office to test different things like EMG and muscle activity and even a home gym or a workout environment or you know, ECG while you're, while you're at work during the day just to kind of do a little bit of self quantification and see what kind of things in your daily regimen affect you.

If I was a serious quantified self kind of person, that is the first thing that would be on my shopping.

List because it's pretty cool. It's, it's, it's on my radar now for sure. Yeah.

I mean, more the fact that it's fascinating that it's possible now than anything else. I've had all that equipment for years, but it was not €120 or whatever. The hardware cost is substantially more than that. It's the fact now that the access to these things is absolutely huge compared to how it used to be. It's not just stuff for researchers anymore, it's stuff for everyone. And that is a very good thing.

Well, obviously there are all sorts of different ways that we could go with this in terms of all the different things that you're researching, but I think that we probably already are making people's heads hurt. So if you're listening in and you want to look at the show notes and look at some of the stuff that James and I talk about, you can go to BenGreenfieldFitness.com AdvancedHRV James, I have one last question for you and that is, is this something that you personally measure frequently on yourself using like an app or a smartphone or something like that? The HRV in terms of self quantification? Or are there other things that you find to be more important when it comes to quantification, or do you just ignore quantification altogether?

The interesting thing about doing a PhD in this stuff is it leaves you with a great knowledge of it and not enough time to train sufficiently hard that you might want to monitor too much.

But even, even not just for training, but just for like, you know, monitoring stress in general.

I have, I have about half a dozen different things, things that do this in my house. Simply the stuff that I've acquired over the years. I've had an idea for a while about something which, something which works quite well. And it's the fact that immediately post exercise you have a very interesting period where you go from having pretty much no parasympathetic activity whatsoever because you've been working hard through to absolutely no sympathetic activity whatsoever because you're not working at all. So imagine me on a treadmill, I'm running, and then I stop dead. The heart rate response after that is a very, very good measurement environment that's been more or less ignored by all the people who do commercial measurement stuff. Now if I'm measuring my response to exercise, that's the thing that I actually use because it's specific to the gym and it's something that you've got control over. The relevant change that happens is something that you've done. You're not just waking up and hoping that all of the different factors that affect your HIV are lined up correctly. You go out and you make sure you've got no HIV whatsoever by doing a bunch of exercise and then you stop dead and you measure your recovery. That's my little personal experiment thing. And as far as I'm aware, no one makes a commercial product for that yet. But that's the one. If I'm not convinced that I'm 100%, that's the thing I measure in myself and I have to kind of hack that together from equipment that I've got around. But for me, not very hard. That's my job.

And so what is it exactly, just one more time that you're actually measuring with that?

If there's, if there's research on that, it's called hrr, which is heart rate recovery.

Okay, Heart rate recovery. Got it. Yeah.

It's mostly related to HIV without being exactly the same thing.

Yeah, got it. I'm familiar with that. That's actually a test that I occasionally do. I call it the five minute burpee test, where you do as many burpees as you can. In five minutes, with the exception that you have to stop if your heart rate exceeds 80% of your maximum heart rate. And then you can start up your burpees again once your heart rate has dropped down to that level. And so what you're measuring is your ability to not only do exercise while controlling your heart rate, but also the ability of your heart rate to recover quickly from hard exercise. So you can jump back into it as soon as possible again once you've stopped.

Assuming you keep your pacing strategy the same, that seems like a pretty good idea for your recovery. When your heart rate goes too high, I would suggest breathing through your nose very slowly with your mouth closed, which.

Is tough to do when you're gassed.

Which is extremely tough to do. But have you heard of breathing ladders?

Breathing ladders?

Breathing ladders?

No.

Absolutely fascinating thing. Very simple, very simple kind of concept. You do one particular movement of one particular exercise. So a kettlebell snatch or deadlift, a fairly light one, something like that. And then you take one breath and then you do two movements and then two breaths and then three movements and then three breaths, etc. And you load it. So doing 20 of these things would be particularly interesting. You don't open your mouth at all the entire time, really, and you breathe. You breathe entirely through your nose. And your recovery and rest is entirely dictated by how much you can slow your breathing down while it's not actually during the exercise itself. So if you take, say we've done five, if you take five breaths very, very fast, you're going to be back to doing the exercise straight away. But if you take them really slowly, you have plenty of time to recover. What it teaches you to do. This is, from my perspective, someone who does sort of mind body research and breathing, heart rate research. This is like the holy grail of interesting phenomena being smashed together. What happens is extremely strange. You get very, very calm when you do it right because you end up decoupling your perception of what's happening to you. Your chest is breathing, you hurt, you want to open your mouth and gasp, but you don't let yourself. When you do that for long enough, you end up starting to ignore the physical symptoms that you have of sympathetic distress. And you find that your ability to control the recovery that happens after the cessation of exercise gets really, really good. I have done these in a lot of different contexts, and the way that it feels is I'm 100% convinced of this. I don't quite understand what's going on with it yet, even though this is the stuff I do research into. There is something extremely unusual going on during breathing bladders.

Sounds really interesting.

If you've got any ideas, or if anyone else has got any ideas, I'd be more than happy to hear them. But it's a fascinating mashup of normal exercise and the kind of stuff I research.

Yeah, so it's basically like a high volume workload that you do at a relatively low level of intensity where you're focusing on like deep nasal breathing throughout.

That's it. The moment you open and the moment you open your mouth, either during, during the exercise or during the respiratory period, you're done, it's over.

That's really interesting. I actually did an entire workout like this a few days ago when I was feeling really beat up and I was at the gym. But I wanted to do something. I told myself I was going to do the weight training circuit, but I did the entire circuit with the caveat that I was lifting at a slow, controlled intensity and couldn't breathe through my mouth. And when I finished, I felt this deep sense of relaxation, just as if I'd done like a yoga session, although I lifted weights for a full hour. But I think it's the combination of perhaps, I don't know if it's parasympathetic nervous system activation being coupled to that breathing, like the deep nasal breathing, or the fact that, you know, baroreceptors in your chest can detect shallow chest breathing and cause like a cortisol release that's been shown in research. You know, maybe it's just like lower cortisol, less sympathetic activation, that type of thing. It's really interesting.

I. Look, your speculation is literally as good as mine on this, but I have absolutely no idea. What I do know is that the state of mind that you've just described is totally 100% the same as my experience with doing these.

Well, if I can find any research on it.

It's a very unusual state of mind that you get and I wish I understood more about it. It's one of those things that's very high on my list of stuff to find out when I have my own laboratory.

Yeah, if I can find any research on it, I'll put it in the show notes for folks listening in. But in the meantime, we should probably wrap. So first of all, if you're listening, go to BenGreenfieldFitness.com advanced HRV where you can see everything from a very nerdy picture of James. It looks like some kind of like a. Like what's it called when they take your photo after you've committed a crime?

Mug shot.

Yeah, it looks like a mug shot. Along with all the articles that we've referred to, some of the research, some of these cool things like the Bitalino for measuring your ECG and your emg, some research on the effects of fish oil on hrv. I'll link to that research article on HRV and blood lactic acid and and some other things. So check all that out over at BenGreenfieldFitness.com AdvancedHRV and also leave your questions, your comments and your feedback over there. I'll also link to some of the easier previous podcasts and articles we've done on hrv. In case this stuff is really making your head hurt, you need some of the more elementary information before being able to understand some of the stuff James and I have talked about. But James, thanks for coming on the show, man.

You're most welcome.

All right, folks. Well, this is Dr. James Heathers and his website is James Heathers.com and Ben Greenfield from BenGreenfieldFitness.com signing out. Have a healthy week.

Visit BenGreenfieldFitness.com for even more cutting edge fitness, nutrition and performance advice. Sam.