Join me, Dr. Mike T. Nelson, as I sit down with Simon Wegerif, the visionary founder of iThlete and a pioneer in heart rate variability (HRV) technology. In this episode, we revisit Simon’s journey from creating the very first HRV app for iOS to his latest work at Lifelight, where they’re breaking new ground in measuring blood pressure and heart rate with cutting-edge technology. We’ll dive into the practical applications of HRV for training, hear Simon’s inspiring story about a health scare that changed his outlook, and discuss game-changers like sleep hygiene, deep breathing, cold water immersion, and mental health for improving HRV. If you’re as fascinated by HRV, performance optimization, and health tech as I am, you won’t want to miss this episode! Sponsors: Tecton Life Ketone drink! https://tectonlife.com/ DRMIKE to save 20% LMNT electrolyte drink mix: miketnelsonlmnt.com HRV Education Course: https://miket.me/hrv/ Enter code hrv100 at checkout for $100 off
Join me, Dr. Mike T. Nelson, as I sit down with Simon Wegerif, the visionary founder of iThlete and a pioneer in heart rate variability (HRV) technology. In this episode, we revisit Simon’s journey from creating the very first HRV app for iOS to his latest work at Lifelight, where they’re breaking new ground in measuring blood pressure and heart rate with cutting-edge technology.
We’ll dive into the practical applications of HRV for training, hear Simon’s inspiring story about a health scare that changed his outlook, and discuss game-changers like sleep hygiene, deep breathing, cold water immersion, and mental health for improving HRV. If you’re as fascinated by HRV, performance optimization, and health tech as I am, you won’t want to miss this episode!
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[00:00:00] Welcome back to the podcast. I'm your host Dr. Mike T. Nelson. On this podcast we talk about all things to increase performance, add muscle, improve body composition, do all of it in a flexible framework without destroying your health in the process. Today on the program we've got Simon from iFleet, which does heart rate variability.
So we're going to do a deep dive on all things heart rate variability. Simon was one of the first people with an actual app going back, oh man, almost, I think we talked about this 14 years now that I've been using the app. For listeners who already know, my PhD was on metabolic flexibility and also heart rate variability.
So I did a lot of measurements on HRV in the lab, and it was nice to actually have an app to do HRV. Which makes it [00:01:00] really practical. So we talk all about that, along with some health scare that Simon had, and what he's doing now. He has another job and some very cool technology that I think you will enjoy.
And if you want to learn more about heart rate variability and other things, you can get on to my daily newsletter. So go to the link down here below. I also do have a course the heart rate variability education course, we'll put a link to that down below also. That I did in conjunction with iFleet.
But you can really use it for any heart rate variability program. I wanted to try to make it so you can understand it. You don't have to know a lot of math. We talk a little bit about math here. But the key was I wanted to create a program that make it understandable and also actionable. Our other sponsor is Element.
I've been drinking some more Element today, once again. My favorite today is the [00:02:00] raspberry. I usually put about one packet in my little hydro flask here that's one liter. Works really well. If you're looking for tasty electrolytes for training and just general life, check them out. And then also check out my friends at Tekton.
For ketone esters, I will be in Colorado briefly doing some work with 'em, filming a bunch of content coming up. And if you're looking for a ketone ether that tastes pretty good, check them out. Most of ketone esters, if you've ever had them taste pretty darn horrible. And the reason you probably need a ketone ester you can get some elevation of ketones with the ketone salts.
But to get higher elevations of actual ketone bodies, the ketones in your bloodstream that do all the work, you're probably going to need an ester, which is just a different type of chemical structure. The downside is most of those taste really [00:03:00] bad. This one tastes good. You've got 10 grams of ketone esters per can currently.
So I'm a scientific advisor to them and an ambassador, so full disclosure on that. But they've got some really, really cool stuff coming out that I can't talk about yet. As soon as I can, I definitely will share it with all of you here. Go to the link below, use my code to save some dinero. And enjoy this podcast with Simon from iFleet, all about the science practicality of heart rate variability.
Welcome to the podcast. How are you today, Simon? I'm very good. Thank you, Mike. Good to see you again. Yeah. Thank you so much for being here. We haven't chatted in a while. I know you've been busy, obviously, we're, we still use the iFleet app, and I originally met you online Man, what was it, like, is it 11?
Is it over 11 years ago now? 10 years?
Simon Wegerif: It was actually [00:04:00] June 2010 when you got in touch. Oh, Jesus! It's been over 15 years, man.
Dr Mike T Nelson: That's wild. And that was I think right when you had the iFleet app was being developed, is that correct?
Simon Wegerif: Well, yeah, I think the the iOS version was available that time, and I think it was iOS 2.
2 or something like that. Yeah, it was very early. It was, it was very early. In fact, I think it was the first heart rate monitor of any kind on, on, on the App Store. So, to go straight from So, you know, to go from nothing essentially to measuring heart rate variability using a strap and a little plug in dongle which captured the radio waves that all the polar type straps gave out in those days.
That preceded Bluetooth, obviously. But Yeah, your first inquiry was relating to whether or not we're going to be able to get the app on Android, which we did manage a couple of years later, took us a little bit longer, but and we started talking about metrics and, and HRV [00:05:00] and how you could use it in training.
And you were kind of wrapping up your PhD at that stage. Yeah, a lot of a lot of data and results you were looking at as well. And we, we bought in a, a very talented mutual friend, Dr. James Heathers. That's right. Yeah, he was there. He did some, he did some good pioneering testing, in fact, on iFleet in the early days as well by looking at that.
Accuracy of all of the interbeat RR intervals, because there were a couple of people around that time who were like really curious about whether or not a consumer product could actually measure HRV accurately, but also with a sort of a healthy scientific skepticism, I think would be fair to say. So, James was one and Andrew Flatt was one of the pioneers.
Dr Mike T Nelson: Yeah, because at the time I was I was pretty doubtful because I, you know, I was measuring it in the lab and we had had probably 20 grand of [00:06:00] used equipment just to measure HRV in the lab. We had to have subjects come in. We had to, you know, hook them up to the EKG. And then you had the, the thing to get the measurements.
And then you had to get the RR intervals. You had to pull that off. And I had to write a freaking. Matlab program to convert some of the crap and and you're like, yeah, we can do this through your phone. I'm like what? I don't know like that'd be amazing. But I have my doubts and I remember talking to dr Heather's about it and he was like, yeah, I looked at it and you know, it's pretty legit and I'm like, hmm And he generally hates everything.
So for him to say like it was good. I was like That's, I'm impressed. I'm interested .
Simon Wegerif: Yeah. So that was good. No, I, I, I became, you know, I, I, I, I guess I became fascinated by the potential for HRV in, it was probably about 2007 and I dug it out in preparation for today. It was an article in a UK Sports Science Digest called Peak Performance, which is a very good little [00:07:00] newsletter actually.
Mm. There was an article in there by coach and Physiologist. Eddie Fletcher, who was a physiologist behind some of the tests. Done in what bike? I dunno whether he is still working. Oh, sure. Yeah, yeah. But yeah, he was, he, he was there at the beginning of what bike, and he had been, he, he wrote a couple of articles actually about using high-end polar watches to transfer RR intervals to a laptop via an infrared.
An infrared link. Yeah. And then once you've got the RR intervals into a CSV file, you could download that, then you could upload it into Excel, and you could start to do, like, you could, you could start to look at trends by using rolling averages, and you could calculate standard deviations and other indications of variance, and, and that, like, reduced variability was associated with progressive loading stress of all kinds on the body and that I found that fascinating from the start and I thought, well, I'd love to be able to do that for myself.
But clearly this methodology is [00:08:00] you know, the novelty of that is going to wear thin fairly quickly. So I started thinking about how you could implement that really quickly. And initially, because I've, I've been employed by Phillips for many years in the U S as well as the UK. I was thinking about a consumer product to do that.
And I was thinking how on earth, you know, am I going to raise all the money needed to make a, you know, a consumer product, like a watch or something like this, right. And then I was at the dentist and I was explaining to my dentist. It was this big South African guy who was like. Interested in all matters engineering.
He used to design Porsche turbochargers. Oh, wow. And I explained to him what I wanted to do. And he said, no, don't do it with a, you know, don't build a special device, just make an adapter for these, for these new iPhone things. And I think it was just about on the iPhone three at that time. And that's what I decided to do.
And I got some help from some friends on, on writing the software, but it was the kind of help whereby I was basically. Yeah, I was [00:09:00] learning during that time and this was the early days of, of coding for iOS and, and it wasn't that difficult really yeah, to create the first version of the product and then, you know, got, got a few very helpful people, you know, including yourself and there was an ex GB Jew athlete as well.
Did some early testing on it and he happened to be a journalist. So he wrote some articles. And, you know, just I look back on it and I think how lucky I was to have, you know, a number of a number of credible people around to give feedback and to test it and to and and to help as well. So that's not also not forgetting.
Yeah, some, some physiologists at the University of Essex and yeah, a few other people as well. Quite a few other people.
Dr Mike T Nelson: Because I think your background at Philips was primarily in DSP, right? Digital signal processing and that type of thing. Because my criticism of people trying to do it was a lot of times it was just the [00:10:00] physiologist trying to figure it out.
And I'm like, most physiologists just don't have a background in the things you would need to, to translate it like they could understand the data and they could tell you all about what the data meant, but they weren't the best people to design something to get the data.
Simon Wegerif: Well, that's certainly true, although a physiologist I've known for a long time, Professor Alison McConnell, who's helped me with some really, really key insights on how the sort of the, the respiratory physiology interacts with, with heart rate and the pressure changes in the chest and all that kind of stuff, which is, which is really fascinating from the evolutionary point of view.
But she had actually, she's actually written a number of lab view programs, but, but probably consumer products, but yeah, so yeah.
Dr Mike T Nelson: And what was the biggest challenge? I mean, my, my guess in looking at some of the early data would be just getting. A clean signal and trying to get the peak of the [00:11:00] R wave.
So for listeners who are not super familiar, one of the main things you have to do is we have the little QRS, which is the depolarization of electricity across the heart, especially the ventricles and that little top pointy spiky R wave. You're grabbing the peak of that to the next peak, which is how you determine heart rate.
But with HRV, you have to be accurate down to like milliseconds. So like super, super accurate and you can't interpret like someone moves a strap or you get noise, you know, as one of these intervals, you want to make sure that it's one accurate to where it is and two, it actually is the heart. It's not some other noise that just got injected into the system.
Simon Wegerif: Yeah, and that certainly is one of the one of the one of the harder aspects of it. And, you know, there's a few ways you can tell and you're absolutely right that, you know, if the, you know, the mean, the mean interval differences. One seconds. That's 1000 [00:12:00] milliseconds. You certainly want to be able to measure that difference of the, you know, to the order of like five milliseconds.
Maybe, you know, so that's that's well under one. That's well under 1%. That's quite like point. 0. 5 percent or so. So you, you certainly do need to be accurate. And you can tell artifacts in a couple of different ways. I mean and, and a lot of it requires just knowledge, first of all, of what the spike should look like, whether it's a spike on an ECG or whether it's the spike on a, on a pulse sensor.
So later on, when we develop the eye feet finger sensor you do also get a, a, a spike there that looks a little bit like an ECG trace as well. It's got this sort of regular. pattern to it, but you need to be able to detect what we call the fiducial point there as well. And that's your sort of your timing reference point.
And those are very, very susceptible to motion artifacts changes in lighting conditions, all kinds of things like that. But they do have a character. One, one thing is they have a characteristic shape and [00:13:00] amplitude. So you can say. You know, if it's not this shape and it's not within this sort of range of heights that we're expecting, if it's kind of much bigger than that, quite commonly, if it's a, if it's a noise spike or an artifact, or if one's missing then, you know, you, you, you reject that when you do HRV analysis you're often, yeah, I mean, you are dealing with, with variation and with RMSSD, which is a commonly used measure you're dealing with variation from One beat to the next beat.
So you've got to make sure that your your beats are in order because if you're skipping one in the middle, because you've said that it's it's an artifact, then you can't compare the two that are either side, they need to be adjacent beats that you're comparing. So you have to make sure that you're Rejecting a pair each time something goes wrong and there's a bit of sort of Sort of a bit of maths and and data cleansing that you have to be involved with there And another thing is just the plausibility of the change between one pulse and the next So if somebody's got a mean pulse rate of make [00:14:00] the calculations easy 60 beats per minute That means that on average the beat is going to be one second, right?
Because that's Yeah, 60 beats per minute is one per second. So that's the mean and you can have a variation there, but it's not going to be half a second. You know, it's it's going to be at least 0. 8 of a second and not more than about 1. 2 seconds. So you can look at, you know, absolute values. And you can also look at these changes, which are the bits you're trying to characterize.
And you can say, Well, that really needs to be within this range, and that can be a range, which is that's normally a range which is indexed by the mean heart rate. So as long as you can do a reasonable estimate of the mean heart rate, which you pretty much always can, then you can use that in order to, you know, calibrate your acceptance criteria for a particular beat in the sequence and for and for adjacent beats as well.
And those are real challenges that, you know, smartwatch manufacturers and and And any situation where there's where there's motion going on. So if [00:15:00] you're trying to measure HRV during exercise or when people are moving or even when they're asleep in bed, Which you know that there are definitely smart watches that characterize your HRV in in deep sleep And if you just even get let a couple of artifacts through you will with HRV you always exaggerate the the the the variation so The, the, the kind of the, you will always make the HRV appear bigger than it really is.
And in that case, that makes your system kind of less sensitive to you know, changes where stress is increasing because where stress is increasing, heart rate variability is decreasing because slightly counterintuitively variation in, in beat to beat timing is normally indicative of a healthy. You know responsive cardiovascular system and, and, and that, that in an evolutionary context is something that's really useful because that allows the body to, you know, adapt to the most [00:16:00] energetically efficient state no matter what it is that you're doing at the time.
And a lot of that variation is then It's then created and modulated by the vagus the, that's the parasympathetic, the rest and, and digest system. So you don't want to, you know, if you're trying, if you're trying to make a system that's sensitive to increasing load, increasing stresses of the different, different kinds of stress then In general, you don't want your HRV values to be exaggerated, and that, that, that certainly is something that, that can and does happen.
So you want to be able to ensure you reject all, as many artifacts as possible so you can, you can reflect the true, often low level of HRV that, that you want to then take action over.
Dr Mike T Nelson: Yeah, because when I was doing it in the lab, I had to manually review every single one. I didn't trust the noise, and we had the raw data, we had the RRs, so you had to sit there and stare at the EKG, look at [00:17:00] the RRs, and then, it was pretty clear when you would find ones, like, you know, what didn't fit.
It wasn't really much of a discrepancy, but, oh boy, that's not very exciting to do for hours on end.
Simon Wegerif: That is what they used to do. Yeah. The history of the HRV goes back to the Reverend Stephen Hales in the, in the 18th century. It's about 1730 or so that he, he was someone who, who did a lot of work on trying to understand the human circulation cardiovascular system.
And he noticed that the pulse got more rapid when people breathe in. which was a good observation, right? That's kind of fundamental, really. So when you breathe in, what actually happens is that you create a negative pressure inside your chest. That's what makes the air flow in down your, down your trachea into the lungs because your, your diaphragm is, is contracting and, and decreasing the pressure in, in your chest, but that also increases what's known as [00:18:00] venous return.
So when that decreased pressure happens inside the chest cavity, it stimulates more blood to be returned to the to the, to the atria of the heart. Into the right atrium and more blood coming in. Actually, it kind of necessitates that the heart beats faster because you've got more blood coming in.
So what's the heart going to do? Is it going to, you know, back up for several seconds or is it going to deal with it? And it deals with it by having sensors in the right atrium. So it senses this increased flow, slightly increased pressure and says, okay, I need to beat faster. And, and, and That's, you know, that's how it responds to those those pressure changes.
Dr Mike T Nelson: Is that then governed via direct connection to the SA node then? Is that how it's making the changes in, if I remember correctly?
Simon Wegerif: Yeah, it is. It is. So you've got these, yeah, you've got stretch sensors basically on the, on the you know, the, the, the junctions in fact of the the, the vena cava as the, as they're [00:19:00] known into the right atrium.
So it, it kind of senses that additional stress and that additional stretch and that stimulates the the, the heartbeat to increase. That's in a, that's in a healthy cardiovascular system.
Dr Mike T Nelson: And that's why on the app, you actually do, you went with what they call paced breathing. So if people haven't done the app, you're looking at it, you're breathing in and breathing out to a set timing.
Simon Wegerif: Yeah, that's right. That was something,
Dr Mike T Nelson: which was debatable at that time. There was a lot of literature I read, because I was even debating, do I do that in my study or not? And there was Yeah,
Simon Wegerif: I'm, I'm still happy with the choice of providing a breathing pacer. I mean, you can ignore it if you want to. And I know that Dr.
Andrew Flatt in a lot of his studies, he, he was just looking for purely spontaneous breathing. Sure. I think that if you've got a mechanism in the body which is dependent on breathing, I don't think nobody would argue [00:20:00] that HRV doesn't depend on breathing rate and depth, right? Anybody who's studied the subject would agree to that.
The question then becomes You know, are you going to are you going to create additional stress by making mental stress by making people follow an animation as opposed to just having them relax and do it all kind of smoothly? And what I found is that people who are used to doing breathing exercises, generally they don't, they don't have any problem with the breathing pacer and it helps you just sort of.
You're only asking people to do it for a minute. So there's not, hopefully there's not much chance of them hyperventilating. Have a nice, a nice slow pace. And in fact, the pace I chose for the pace that came out of a study, which looked at the mean. breathing rate of a group of group of club standard runners, basically.
And that breathing rate of about seven and a half breaths per minute is about half of that of the general [00:21:00] population. And that shows you that athletic people, you know, that they have some. some really good adaptations, one of which is that, you know, their oxygen exchange and their lung capacity are just much better than the average population.
So they don't need to breathe at 15 breaths a minute. You know, they breathe at seven, seven or eight breaths a minute.
Yeah. Which is crazy low. Like, I mean, I've looked at
Simon Wegerif: it is, you know,
got hundreds of data on aura now through just my own practice and through doing work for a rapid health optimization and even on some of their high end athletes.
I think the lowest I've seen during sleep is 11, I think. But it's. It's wild how you'll see some, not always the case, but you will find these outliers who have a high VO2 max, are pretty well trained, and their respiratory rate at night is 16, 17, 18 breaths a minute, which is pretty crazy.
Simon Wegerif: That is, yeah, yeah.
And [00:22:00] perhaps not what you'd, perhaps not what you'd expect. Definitely not what you'd want. No, that's not, no, that's not what I expect. And, and six breaths per minute is a special rate in in meditation. Because at that rate you then synchronize the, I mean, it's, it's kind of, Breathing is one of the very few mechanisms in the body which runs autonomously, but you can consciously override.
So, you know, you can choose your breathing rate, but 99 percent of the time, you're not thinking about it at all. And it continues. So six breaths per minute is, is a special rate because that brings your breathing the changes in blood pressure that occur because of this, this effect whereby you're changing your pressure inside the chest with, with breathing that then co is coincides with.
A compensatory mechanism, which is called the baroreflex and the baroreflex in most people works at about 0. 1 hertz, which is, which is six breaths per minute. [00:23:00] So what you can do then is you can actually deliberately create big peaks and troughs in your blood pressure at a rate of. You know, once every 10 seconds, basically, for the peaks and troughs.
And that is supposed to have a a beneficial effect. Not only just transiently, but, but over the longer term as well to help. Help relieve, you know, potential hypertension and sensations of anxiety as well. So it's, it's, you know, it's a meditative breathing rate and I think the reason why that works is because it accentuates these peaks and troughs and may act as a kind of reset.
to the body's sensing systems, the baroreflect baroreceptors, which are located in the, in the neck, in the carotid arteries, in the, the aortic arch and perhaps other parts of the system as well. But I'm sure you probably know more about that than I do, but
Dr Mike T Nelson: yeah. And on that, what is your thoughts? You, if you have an even bias to inhale, [00:24:00] exhale would be five seconds in, five seconds out.
Would you bias the exhale at that point to try to bias more of the parasympathetic system like a four second in, six second exhale, or what are your thoughts on that?
Simon Wegerif: Yeah, my friend and colleague Professor McConnell, who's, who's, who's done a lot of consulting work with on cardio respiratory interactions in any of the experiments I've done with her.
She, she specifies an equal inhale, exhale, and not really any pauses in between either. It's just sort of a constant in and out. In and out. Yeah. I, I've certainly read I've, I've seen it put down as an argument that you should extend the exhale because that will mean then that at the end of the exhalation, you kind of have a lower heart rate and perhaps might bias the heart rate lower overall, but I haven't seen any experiments versus, you know, equal inhale [00:25:00] and exhale that conclusively make the case for that, that you end up with a lower mean heart rate at the end of the exercise.
Dr Mike T Nelson: No, it's Is that similar to what kind of the heart math people do, it's related to the coherence effect then, correct?
Simon Wegerif: Yeah, that's what, yeah, that's what people refer to as coherence is when the, the, the deliberate sort of blood pressure waves that you're introducing with your paced breathing coincide then with the resonance of your baroreflex.
And you can get some pretty big peaks and troughs in your blood pressure there. I don't remember the figures off that. The top of my head, but I would, I would expect it to be more than 20 to 30 millimeters of mercury difference between the peaks and troughs.
Dr Mike T Nelson: Yeah. And that kind of fits my general theory of what I just call HDR or human dynamic range, like what are things you can do to increase the range, the low end, the high end, and then kind of the variability in between, right?
So if you [00:26:00] can do something that's not let's say exercise related, obviously exercise can, you know, massively push up the high end of blood pressure. You know, but just by altering and playing with breathing, you can basically create the, a bigger range at rest. I think is probably going to be beneficial because a lot of people over time, whether it's temperature, exposure, heart rate, sympathetic, parasympathetic.
Metabolic flexibility, carbohydrates, fats, like they just get kind of crushed on both ends of these, these systems. And when that happens, it variability goes out the window and then all these systems like just start falling apart.
Simon Wegerif: Yeah. So, so kind of helping them to reset their end stops rather than just letting them, you know, sort of fur up somewhere in the middle is, is quite,
Dr Mike T Nelson: I
Simon Wegerif: think, you know.
Very
Dr Mike T Nelson: cool. And then if we fast forward to today, oh, the last part I was going to make too is that I think you were the first people to say [00:27:00] you can get away with 60 seconds of data acquisition. Obviously you published work on that, where I think even the MegaWay people were doing at least three minutes or five minutes, like a lot of the clinical measurements were, you know, several minutes or even longer.
And I thought that was like super cool, because Even with that, compliance is always going to be an issue when you're requiring someone to do a dedicated measurement. So if you can get that measurement to be accurate in representation of what's going on in a shorter time frame, I thought that was super cool because A lot of the research stuff was like, well, we don't care because people are going to come in the lab and we're going to watch them for five, 10 minutes, whatever.
But I think you understood that when you release it as a consumer device, most consumers are not going to sit there for 10 minutes every morning just to get a measurement.
Simon Wegerif: No, they're not. So I always had a minute in mind as a target, but I was, I was super happy. I will admit when I'm working with. Well, these physiologists at Essex [00:28:00] University, Dr.
Gavin Sandercock he, he pointed me to research which showed that with the measurement, the measure I was proposing this RMSSD, which is subsequently become really, really popular the. We could certainly get by with 30 to 40 seconds of good quality data. So I thought if I make the measurement just under a minute, then even if there is some corrupted data in there, I can still get 30 to 40 seconds of good stuff out of it.
Dr Mike T Nelson: Yeah, that's super cool. And why did you pick RMSSD? Which, my bias, and again, looking back in history, I would say that was the the correct one. Obviously, I've been more biased towards these time domain ones. But, what made you pick that measurement? Because, even back then, like when I did my research, I ran it through Kubios, there's, you know, you could pick time domain, frequency domain, there's non linear domains, there's all sorts of stuff.
What made you kind of pick that one?
Simon Wegerif: I, I think a couple of reasons. I did have a look at different [00:29:00] metrics. I didn't think it was going to be practical in the capabilities of the phone at that time to do a frequency domain analysis, which the other main option that I was looking at. Also, I think it might have been James Heathers pointed me to some of the controversies about the interpretation of the in particular, the frequency domain ratios people talked about.
F divided by LF and we don't really know what LF is. So why just dividing something that you might understand by something isn't understood, you know, why does that produce a sense of numbers though?
Dr Mike T Nelson: So it must be cool.
Simon Wegerif: And I thought I was going to be a bit complicated to implement and it would really require people to do the pace breathing as well.
So I wanted to make the pace breathing, you know a useful prompt, but not a mandatory. I, I also knew that SDNN which was the, which was the first kind of medically deployed HRV measure. That is the one that people, you, you, you made reference [00:30:00] to sort of looking at ECG traces and sort of marking valid versus invalid beats and what they did to calculate SDNN was they would, they would simply use a ruler on the, on the ECG trace and they would measure the.
The differences between the adjacent our wave peaks, and then they would simply calculate the standard deviation of all of the good ones. And that was the first that was the first HRV measure. And. It was shown in research that that was a very sensitive indicator when people were brought into hospital with having had a heart attack.
It was a very good independent prognostic indicator for how, how likely they were to survive the first 24 hours. I mean, it sounds rather dramatic, doesn't it? But HRV was used for that in the 1980s, I think, or maybe even a little bit earlier, maybe 1970s. So that was another candidate. But I wanted something that was more sensitive to the parasympathetic nervous system rather than the all [00:31:00] encompassing SDNN.
And that meant that I had to be able to sense the changes that were induced by breathing and RMSSD was in the literature as a way really of looking at the adjacent beat interval differences. And that essentially acts for us engineering types as a high pass filter. So that was going to separate out the the, the respiratory component from the baroreflex and other very low frequency effects that you get from like thermoregulation and various other mechanisms that are going on the body.
So RMSSD was the simplest calculation, which would actually quantify the effect I was looking for. I think that's probably the. The short answer, but
Dr Mike T Nelson: yeah, and I think with the available computing power was relatively easy to do the math from a processor standpoint, correct?
Simon Wegerif: It was, but the problem with RMSSD as a rule measure is that it has some.
It has some good properties. We just [00:32:00] mentioned it's, it's able to separate out the effects of the parasympathetic nervous system and breathing. But it's not a good measure because it's it in human beings, it's highly asymmetrical. So it's what you call a positively skewed distribution. So if the population mean for our MSSD is about, I can't remember what it is, 25 something like that, then you haven't got.
to go in the negative direction before you kind of get close to zero. If you get below 10, then, you know, that, that's not a healthy system by any, you know, that's not a healthy vascular system. Right. But on the high end to Ironman. triathletes, you can get 150 or even 200. So you've got a really big asymmetry in the distribution.
So you've got lots of variation on the positive side and rather little variation on the negative side. So the thing to do then is to take Start with the natural log and see if you get a more symmetrical distribution, which we did [00:33:00] and, and that was great. But then you end up with a scale that's not very intuitively interpretable.
So you get something that will like go from, I don't know, 2.5 to to 4.8 or something like that. And you think for consumer product, that's .
Dr Mike T Nelson: Good luck with all that. It's not gonna, that's just not
Simon Wegerif: exciting as a consumer scale, is it? So let's multiply it by. 20. Okay, so we multiply it by 20 and that then gave an intuitively interpretable scale, which went from like below 50 on the low end.
So I had a, I had a a boy's curry night recently with some some cyclists that I've known for a long time. And a couple of them were, we were reminiscing over early days of iFleet HRV measures. And both of them, in fact, had had, really bad flus, this predated Covid, so they'd had like swine flu, one of them, and another one had really other bad flu.
And they would normally have an eye sleep measurement of 80, 85, they were quite aerobically healthy guys. [00:34:00] And, and they went down to like in the 30s. morning and they said they knew just from that HRV measurement that they were they were getting quite sick. And in one case, one of them was in hospital within a few hours after that got so sick.
So the the intuitive interpretability of the scale was really important. So You know, a lot of people are in the like 60s, 70s, maybe low 80s or so, if you're quite athletic, quite aerobically fit. We certainly have seen values of 100 and some people think there's a hard stop at 100 on the i3 scale.
There isn't, it can go over that. I, I, I think the highest ever was something like 112 and that's an aboriginal Aussie rules professional football player. So never seen a, never seen one higher than that. And on the low side, like I say, people who are really quite sick will be in the thirties. And I remember I did a couple of consumer electronics shows actually at in Las Vegas.
We had a stand there and, and I had [00:35:00] a journalist come over who wanted to write about iFleet. And I think this is, I don't know, maybe 2014, something like that. And he was, he was quite overweight. And he had diabetes and he took his measurement and it was like 38 and he just without me telling him about the scale, he immediately started apologizing about his lifestyle.
And I thought, okay, well, this scale works, right? This guy. He needs to he needs to do something about this health condition. Yeah. So anyway, so that's where the 20 times the natural log of RMSSD came from. And I was pretty happy about that also for another reason. And that's because one unit was basically 5%, a 5 percent change.
And that was about the. I don't know whether smallest worthwhile change is a, is a, is a, is a concept that's worth talking about it in much depth, but it's, it's quite often used in sports science. So, you know, we didn't need to go to decimal points and one point, you know, [00:36:00] was worth, you know, worth, worth some kind of appreciation.
Dr Mike T Nelson: Yeah. And I thought that was actually extremely useful because. When I was doing research, trying to explain HRV to people was a freaking nightmare because it was, the concept was new. So they didn't really quite grasp the concept. And then it was, if someone did know about it, it's like, Oh, what measurement did you do?
Now the scales are different. Now the numbers actually mean something different. Now there's the argument about like, you know, James Heathers and those guys about frequency domain. And what does it actually really measure? Is it really useful? And it seemed like. The rush was to get all these measurements into an app and some of the other ones I looked at had good intentions, but in terms of useful to consumers who are not hardcore researchers, I, I kept testing out a bunch of them and all they did was drive me batshit crazy because even if they were valid, now I had to explain to a customer [00:37:00] of, well, okay, so your time domain actually changed a little bit here, but the high frequency domain didn't move as much as the low frequency domain.
And it was just a nightmare. It was so nice to have. One number that was relatively intuitive. Okay, when your number is higher, you're more parasympathetic. When your number is lower, you're more sympathetic. And that was nice to, and then also have the qualitative indicators on there. And nothing else. Like, that was, to me, and still is.
The best for someone actually having to use the device with people who are not HRV experts. I don't expect my athletes to be HRV experts when they're, when they're doing it.
Simon Wegerif: No, and that, that was always the, the aim from my point of view was to, was to have something, a tool that was easy to use, easy to interpret, hopefully easy.
for coaches to use as well. We did a team system and we did a coach system and it was popular with team sports for a while. But yeah, I mean, there's so many sort of politics and dynamics in the, in, in professional teams. [00:38:00] Yeah. An HRV reading, you know, isn't going to be used in practice to make many decisions, unfortunately.
So it is, it is useful, but it's, you know, it's not going to be not going to be as acted on as if an individual athlete, a pro athlete or or, you know, amateurs are using it. And we've had plenty of people use it for, You know, wellness and recovery from conditions as well as as, as athletes training my, my initial interest was from the point of view of trying to improve my own training.
And I'd always, I, I've, I've always had the tendency to want to train with people who are better than me, which is, which is good on one level, but if you do the same volume and intensity who are better than you, then there's only one certain outcome. You're going to get sick or injured. Yeah, so I kind of HRV was my tool that told me when to back off.
Dr Mike T Nelson: And then if we fast forward [00:39:00] to today is the HRV app still being supported? Like, what is kind of the status of where we're at right now?
Simon Wegerif: Yeah, so the HRV app is still available on the app stores. For sort of a couple of different reasons, really, I've decided to close down the web service, iSleep Pro.
One of them was that the hosting was getting super expensive and, and costly to maintain as well. We needed to do a major database upgrade, which was going to cost a lot of money. So that was one reason. Another reason was that I've got a bigger So, Yeah, I've got a day job now, which is four solid days a week, which, which perhaps we'll come on to in a moment.
And the third one was that I, I had a bit of a, well, sort of significant health scare, really, I got diagnosed at the end of 2023 with prostate cancer, which was starting to spread, which is a little bit scary. I ended up having robotic surgery in January last year, so we're coming up to the end of this.
Oh, wow. And, and, and I [00:40:00] cannot, I cannot sing the praises of the Southampton University Hospital Urology Department loudly enough. They've been absolutely amazing the whole way through. But the symptoms that I had for it were really quite mild, Mike. So I was feeling a bit more tired than usual.
And my partner, Julie, noticed that I was eating more than usual but not exercising more than usual and losing about a kilo a month. So that, that little constellation of my, my HRV wasn't, it wasn't down in the dumps, but it wasn't kind of at its normal level, but, you know, I thought there could be several reasons for that.
So it, it was, you know, HRV is sensitive, but not specific, I suppose. Right. . You know, I went to the GP, you know, had the a small battery of immune tests, which came back. Absolutely fine. Other blood tests, fine. And then she sort of called me up and said, Hmm, you're nearly 60. We better give you a PSA test just to be sure.
So I had a PSA test and sure enough, that was Like two or [00:41:00] three times what it's supposed to be Yeah, but but recovery i'm just gonna show this on the on the screen So this is this is a year's worth of of data just on the screen there. I don't know whether that's
Dr Mike T Nelson: Oh, yeah, well, it looks like it's definitely gone up over time.
Simon Wegerif: It has gone up over time. So Yeah, I mean that that's charted my That's charted my recovery in HRV and I have to say that I, I would say how I feel and how energetic I am has corresponded pretty well with that upward curve. So yeah, so, so that's good. But, but nowadays I'm the, I'm the chief scientist for a company called Zim, which has been developing a product called Lifelight, which Which the, the aim of it, and we're pretty close to realizing it now, is to be able to measure blood pressure and heart rate by just having you look at a camera on a phone or a, or a tablet for for 40 seconds.
So this does use the similar [00:42:00] principles to what I first explored with the finger sensor, which is known as PPG, photoplethysmography. But this uses remote PPG, so it actually senses a phenomenon that we sometimes refer to as micro blushing. So although we can't see it when we're looking at each other now, the blood flow in our cheeks is also, you know, the capillaries in our, in our skin everywhere, and in the cheeks in particular, is being modulated by the heart rate.
And not only can we measure heart rate from that, but we can also look at the morphology and HRV and other things of that. And we can then use AI tools to to estimate and predict somebody's blood pressure. So we're on the verge of having that. Having that certified as a as a class two medical device.
So that's that's quite exciting So I'm giving a lot, you know, a lot of my time and energy to to running the running the science for that And we've done a load of clinical studies and Yeah, I'm continuing to do more specialized studies with it. In fact into We were [00:43:00] just starting one in a In a neonatal ICU we're starting to do one with patients with atrial fibrillation as well.
To help them sort of better understand their condition.
Dr Mike T Nelson: Are you able to pick HRV off of that then also, it sounds like you said?
Simon Wegerif: Yeah. So, I mean, you've got some more technical challenges to doing it. Yeah. The signal is, is much weaker than you get from a dedicated sensor. But we, we've, you know, a lot of our, A lot of our work has been on signal processing to clean up the signal and we've found all kinds of ways to clean it up and make it look like a nice pulse, so, and to have the properties of the pulse.
One of the good things about sensing signals on the cheek is that it's actually quite, it's directed fairly you know, fairly closely to the output of the heart, the aorta. So you're, you're, you're sort of sensing without too much distance and obviously without putting needles and [00:44:00] catheters and cannulas inside people you're, you're kind of sensing their central blood pressure waveform, which is the best place to sense it.
It's better than the arm or the wrist. It's, it's kind of a purer version of what's going on.
Dr Mike T Nelson: And I would imagine there's other Applications for that in terms of, I don't know, the one place my brain goes to is. I just think about all the, the zoom conferences and everything like that. Or even just if I'm doing an assessment on an athlete remotely, like maybe in the future, there'll be little, everyone will have their little biometric below their thing that shows changing heart rate and HRV and stuff like that.
I don't know.
Simon Wegerif: Well, yeah, that's, that is possible. That is definitely possible. I mean, our, our applications are initially you know, population health screening in particular to help identify undiagnosed hypertension because, you know, hypertension is often referred to as [00:45:00] the silent killer because you won't necessarily get symptoms until, until something pops and you definitely don't want that to happen.
And also to, you know, Helping people to track their, their blood pressure at home. So, you know, to help reinforce good behavior patterns, whether that's taking the medication on time, or whether it's exercise, reducing alcohol, you know, the other, the other kind of things that we hope people will do by measuring their HRV frequently is also, you know, also true of their blood pressure.
So yeah, life flights are useful. Hopefully going to be used in lots of places on lots of phones. Very
Dr Mike T Nelson: cool.
Simon Wegerif: And as any
camera can grab that data, right? Just a computer, phone, anything that you've got a high
Simon Wegerif: quality camera. It can. You need to have good low level control over the camera. So at the moment, you know, that's that's, you know, using the full API's programming interfaces that are available in iOS for Apple devices and Android.
As well, the camera control [00:46:00] APIs, because we need to be able to control the frame rate and make sure that that's accurate, because that determines all of our sampling intervals. Sure. And construct the waveform. Afterwards also exposure is very important. So, you know, a lot of the time selfie cameras are, you know, continuously adjusting for the best aesthetic effect.
And that's not necessarily what you want from a, from a sensor, you know, that they'll be adjusting to. You know, give an exposure, which looks, you know, makes your skin look smooth and night color and healthy and things. So there's lots of increasing amounts of aesthetic image enhancement software that go into a camera.
So you've got to make sure you get the signal out before, before those have had a chance to yeah, to distort it in a way that's not helpful when you want to, when you, when you just want to sense, sense what's going on.
Dr Mike T Nelson: Is that true of all cameras now? I was talking to my tattoo artist and he was saying when he was trying to take photos of certain things that [00:47:00] a lot of the new phones now are just auto correcting or trying to run auto correct on everything just as the norm in the background now.
Simon Wegerif: Yeah, that's true. Yeah, and the more you pay for your phone, then the more of that software
you
Simon Wegerif: get, which makes you look great on, on Insta. But yeah,
Dr Mike T Nelson: that's kind of wild. And it's so funny that it's like, until I talked to him about it, even having this conversation with you, like. I would have never thought of that.
And the fact that it's kind of done for you running in the background. I don't know if a lot of people would, would know that. And I don't know. It's kind of creepy to me.
Simon Wegerif: Yeah, but you, you do kind of know, or you do find out if you're not naturally a good photographer when you start using like a a little digital SLR camera that doesn't have all of this image compensation, you think.
You, you think you're going to take better pictures with it than your phone. Well, that's not necessarily, you [00:48:00] know, you're going to find you've overexposed some areas and then you're underexposed others. And, and in fact, for, for most people, most of the time, the image processing software in the phone is, is what allows them to get good pictures.
And you have to work pretty hard with a, with a, with a, you know, with a camera that doesn't have that software in it to, to, to get good effects.
Dr Mike T Nelson: And having a health care like that, did, I would say, I assume it made you kind of re evaluate some different things, like do you mind sharing like that process?
Simon Wegerif: Yeah, I mean, it's, it's quite scary initially, no doubt about it. It certainly, and, and me getting diagnosed with that made my brother immediately go to his GP and get a test, and sure enough, he, he had, a high PSA level two. He actually chose a slightly different treatment route. He went he went with radiotherapy, which I don't think it was [00:49:00] really an option for me.
Everybody was saying, you know, you're, you're, you know, you're, you're healthy, you're fit. Go for the. You know, go for the surgery option. And, you know, historically, prostate cancer surgery has been a pretty scary thing right? Back in the 1970s. Yeah. Eighties. I think the, you know, the, the, the 50% survival time was about five years or so, you know, following.
Oh, wow. Yeah. And now with robotic surgery. I mean, it is incredible. You know, I can't help it as somebody who's interested in medical engineering, just admiring the, you know, the process and how much that is advanced and you just have a I think it's about five or six you know, small holes in the abdomen, all of which have like completely, you can't even find them now for the, for the various arms.
Dr Mike T Nelson: Yeah.
Simon Wegerif: Laparoscopic tools. And, and they do all of their, all of their stuff inside and recovery is. You know, is, is, is quite [00:50:00] quick, really. Well, it's, it's quite quick for, I would say, for the initial you know, the initial wounds and things like that, but, you know, there are side effects from that kind of surgery, and they can take weeks and months for you to get over.
And, you know, your whole system has been disturbed, and I think that's why we kind of see that. that HRV was sort of bumped, bumped down a few weeks after surgery and then since May last year. So that would have been, that was effectively three to four months after surgery. It's just kind of kicked up and the, the whole time, the whole time since, but I w I was certainly worried that I would never be able to get back on a bike again.
I'd never be able to sit on a bicycle saddle again. And that. You know, it's that that's been fine. I read lots of online articles from people, you know, who were keen cyclists who'd had this kind of surgery. Does it cause you to reevaluate? I think it kind of, it does, obviously that you think, you know, you've had a condition.
And, and with you know, the recent diagnosis [00:51:00] of of, of Chris Hoy, the, you know, the, the, the Olympic cyclist he had stage four prostate cancer. I was only like one half a level below that, but his aurorae stones and, and you think, well, that's lucky. So I definitely have, you know, Julie to thank for making me go along to the, you know, the, the, the primary care practice and, and get.
Get some tests done because I'd left it another few months, you know, it could have been worse So that's an advice for all those men out there who are perhaps in their late 40s early 50s You know, if you've got any history of prostate cancer in the in the family then, you know, do get a PSA test done because You know, you definitely it is something that can can grow and and linger inside you without you having any strong symptoms, you may not, you may not realize that you've got it.
And then once it starts spreading to the bones and the bowels and other places, then it's, it can't be cured at that at that point can only be managed so [00:52:00] I just feel. Really grateful for great care. Yeah, I mean, both people close to me and people, you know, never met me before in the, in the urology department, but, you know, always caring and quite often with, with some good little dose of humor thrown in.
Oh,
Dr Mike T Nelson: that's good. Yeah. I, for a while I started looking at blood work on clients like many, many years ago in the past, and then I, I kind of stopped in all honesty because I wasn't really sure what I was looking at. And I was like, eh, it's kind of a legal liability. I'm not trying to replace their doctor.
I'm just using it for performance stuff. And then starting probably like five or six years ago, I started doing it again because I realized this is usually more men than women, but sometimes women too. I would ask guys, I'm like, okay, you're, you know, 47 now. When's the last time you just had a basic blood panel?
And most of the time, although it has gotten better lately, they have no idea. Like, if you can't remember, it's [00:53:00] been way too long. And you're like, okay, go to your dog, whatever. And it's like, do you even know who your doctor is? No, I have no idea. I'm just like, ah. So that even if I can just get them to do something, even if it's through a direct lab thing, they can run it on their own, at least if there is something wacky, then we have data to be like, yes, you definitely need to go to your physician, like now, because, you know, there's not something I'm going to help you with.
There's something you need a physician to deal with. But it's crazy how even just basic stuff like that, just still, even now is I think very underappreciated and not done.
Simon Wegerif: Yeah. I mean, get, get some objective data because you know, your, your body may not be giving you. You know enough feedback for you to identify that thinking back on it, though, I, I did have some unexplained kind of poor I don't know what's poor endurance performance.
So I've always regarded myself as an endurance [00:54:00] athlete, somebody who can like do these semi competitive cycle rides around like the Island of Mallorca, 300, you know, 200 miles, do that. And Oh, wow. Great. And I've done that several times and, and I'd done the, what's called the Etape du Tour, which is the stage of the Tour de France that amateurs can do.
And it's all kind of organized. It's about 10, 000 enthusiastic amateurs do one, usually one of the most challenging stages of the Tour de France for that year. And I did that in 2023 in the summer and it was up to. Kind of resort called Mausine in the Alps. And I remember getting, it was a hot day.
It was like 41 degrees centigrade. I don't know what that is in Fahrenheit anymore. It's like a hundred. It's hot. It's hot. Properly hot. And there were like people sitting by the side of the road with their, with their heads in their hands. Cause just, you know, they were, they were early stages of, of heat, heat exhaustion.
Yeah. And I made it to the, to the top of the resort, but I, you know, I, I, I got, [00:55:00] you know, tunnel vision and, and luckily when I got to the top of the, top of the last climb one of the, one of the helpers or one of the, you know, the race kind of helpers said to me, you know, in French, which luckily I can speak, she said, she said, don't cycle down yet.
Please give yourself 10 minutes, have a sit down. Before you go down to the, you know, to the finish line and that's, that's kind of a hard advice to take, but I knew somehow she was right. I lay down on the ground and I was just out. I was asleep for about 15 minutes. Oh, wow. Yeah. I mean, from lying down, you know, I just went out like a light and then I woke up 15 minutes later and You know, everything sort of came back into focus.
I got back on the bike, went, went down, did the descent, which was quite a dangerous descent. And it was very hot. And I was, I was very glad I'd done that. But I thought afterwards that that, that performance was not, you know, I couldn't really explain why I had felt so tired. And, and I, I [00:56:00] spoke later to the, you know, the urology specialist and they said the stage.
Of tumor that I had had been growing for a long time. So it probably was probably already taking a toll on my system when I was doing that. So, so sort of unexplained underperformance, I think would be the coaching term for it.
Dr Mike T Nelson: Yeah. And those are always so hard to figure out even on yourself. Yeah. You know, because you look at all, I mean, I've had this happen multiple times.
And even, even kind of now I'm thinking like, yeah, do I need to zap my scars or something weird going on? Cause like training performance is pretty good. Sleep is good. Nutrition is pretty good. But my HRV is still much lower than what it normally is. So then you always wonder, okay, is it work stress? Is it additional things?
Is it, and it's always hard to even pin down what's actually going on too.
Simon Wegerif: Well, I mean, one of the, one of the consistent sort of benefits, I think of people [00:57:00] using ithlete and probably HR, other HRV apps and, and, and wearables as well. Is that, you know, even if you think that you're a pretty dedicated sports person or athlete, the biggest, the biggest source of stress is your daily like, you know, life stress from work.
mental stress, financial, you know, emotional worries, that that is the stuff that really dominates a lot of people's, you know, HRV and their ability to recover as well, because your body sort of sums up all of the stresses together. So it kind of adds up the effects of the mental stress. Chemical stress and and training stress.
And you know, what you experience what you see via HRV is the consequence of all of those stresses added together. And although you think you might work pretty hard in a workout, that doesn't that doesn't normally dominate your your your average stress that's really dominated by mental emotional work stress.
Dr Mike T Nelson: Yeah, that's [00:58:00] My sort of goal, if I was only doing performance and, you know, didn't have to work and have a job, you know, there's stuff, whatever, or it could, you know, reduce some of that stuff is to actually have training be like the number one stressor that changes my HRV, you know? Cause like, if that's one of my red flags with an athlete of if we just pound your nose into the ground multiple days and your HRV isn't changing much, and it was already kind of on the lower side to begin with.
Okay, that's telling me something's going on in your outside life that's very stressful. Even if your nutrition is good. Even if your sleep is good. Like there's something else going on there where the athletes who have that more intact, like you can definitely see how their training and stress is directly changing their HRV, which to me is a good thing because one that's more controllable till we can adjust that.
And three, that's telling me your outside life in terms of stress level is, is pretty good. Like that's a good thing.
Simon Wegerif: Yeah, yeah. But I think that's a, that's a luxury [00:59:00] for the minority of athletes. Oh, a hundred percent. Training stress dominates their HRV, yeah.
Yeah, when I first started looking at it, I thought, Oh, if they're a professional athlete, then, you know, it's, their training stress is always going to be the number one thing.
And in some cases, that's true, right? They don't have anything else to do, air quotes. But in some cases, it was. It was almost worse, you know, if they've got contract obligations, they've got, you know, other things they have to do, they've got multiple day practices, maybe they're in season and you then realize that, oh, wow, like this may be their only job, but it has so many other sub components that are still pulling at them, even though they're professional athlete and don't have to go to a, you know, air quotes like day job.
Simon Wegerif: Yeah. Yeah. And, you know, they've got pressures to perform as well, haven't they? You know, it's not, it's not a happy position often being a, you know, being a professional sports person. It's a limited duration of [01:00:00] career and, you know, you want to make the most of it. So,
Dr Mike T Nelson: yeah. And last question as we wrap up, I get this question a lot, so I'm super curious on what your thoughts are. If, what would be your top four things for someone who comes to you that says, Hey, I'm bought into HRV, I like using the device, I measure it each morning, we're doing all the good, you know, ways to measure it. But my HRV is still kind of low.
What would be like your top four things to increase your HRV?
Simon Wegerif: Hmm. Yeah, I I think there's a few things which are you know, fairly well proven to help here. And probably the number one is like I mean, not only sleep duration, but sleep hygiene, sleep quality. So try to get solid restful sleep, try to avoid the temptation of that, you know, that extra beer or extra glass of wine close to bedtime, because although you may get to sleep more quickly, it will.
definitely interfere. And one of the, you know, one of the comments I've most [01:01:00] frequently had back is, you know, I didn't realize until now, you know, how much, how much, you know, that, that would impact my recovery, having that extra extra glass before. I've even
Dr Mike T Nelson: seen the type of alcohol, obviously the dose matters, but I've even seen the type of alcohol make a difference too, which is crazy.
Simon Wegerif: Yeah, I can certainly imagine that. Another one would be, Breathing, so, so deep breathing I think is very helpful. And I, I was amazed when I first did this is going back quite a few years when I first did my own Little Coherence app which basically sensed the changes which were happening in HRV due to the barrow reflex in my body.
And then. It generated the breathing stimulus from that, so it sensed the direction of the change and created the, you know, basically made the animation move either in or out to make my breathing quickly augment that [01:02:00] pattern. And I was really surprised at how much my HRV jumped up from doing that. And it wasn't a temporary thing.
It was like something that was kind of locked in for the long term. So that was. That was good. And it might have, you know, what we discussed earlier about, you know sort of pressure sensor resetting mechanism that might have been. You know, what was going on there. Is that app available? Because I know everyone is going to ask.
Yeah, no it's not. I never made it. I never made it commercially available. No, I didn't. So, no. I don't know. I might dig it out sometime. Rebuild it. I think it's probably, I'm sure it's expired, but it could be a useful thing, yeah. I think cold water immersion is something that I'm quite fond of, and I think it's, it's really quite therapeutic, not only for your HRV, but for your immune system as well.
There's some really nice data on how just even simple things like turning your shower to fully cold at the end [01:03:00] of your shower, it makes you sort of zing with energy and, and, and, you know, my experience that helps boost your HRV as well. And I, I guess there's probably, there's probably a lot around mental health, meditation, not beating yourself up too much, spending time with friends, all of those ways which help to relieve the, the buildup of, of daily mental and emotional stress, which, you know, we were just discussing tends to dominate.
So whatever works for you in terms of making you feel good, making you feel happy, that, that is gonna, HIV as well.
Dr Mike T Nelson: Awesome. Any other tidbits of HRV? My last question I had is, is there anything really you think is kind of out there or things you suspect may be true, but we just, we just don't have any research on it yet since you've been in the HRV space now for, you know, decade and a half longer than that when you first [01:04:00] started coming up on two decades.
Simon Wegerif: So something I've been intrigued by for a long time, at least one of those decades, is whether or not by measuring the change in HRV during exercise, we can accurately detect People's thresholds. So they're, you know, they're, they're respiratory threshold, their lactate threshold. There is some evidence to support that, but there's not, you know, the studies haven't been done on enough people and precisely enough to then be able to say that, you know, we can definitely measure.
And, and if you're, if you're an endurance athlete, you want to know those thresholds very precisely. And the only way that you can really get that done is by you know, going to a proper sports performance evaluation lab and, you know, sitting on an ergometer or running on a treadmill and, and looking at your, your, you know, your respiratory quotient.
Dr Mike T Nelson: Metabolic heart data.
Simon Wegerif: [01:05:00] Yeah. Yeah. Metabolic heart data. I'd like to think that by using, you know, a good quality chest strap And looking at HRV, and I don't know what measures would tell us that exactly, you know, it would be, whether it be detrended fluctuation analysis, something to do with you know, a reduction in entropy maybe just simple, a calibration of threshold values of RMSSD, I've seen, I've seen evidence that all of those can be used, but they're not, they're not currently, you know thought of as being precise enough to replace metabolic heart testing.
Dr Mike T Nelson: Yeah, my, my thoughts on that would be if someone's listening and they want to contact us, like having a non invasive with zone 2 being all the rage now, and my guess from, I'm not completely up to date on that literature, but from looking at it briefly, I think that may be the easier one to detect out of all the zones.
And just having a zone two [01:06:00] detector where you just have your heart rate strap on. You've got maybe another little app, a little, like a temperature gauge that fluctuates up and down that says when you've crossed it or when you're getting close to it, because we know that that can change also on a day by day basis.
You're probably not going to go all out Peter Atiyah and, you know, prick your finger for lactate all the time, which definitely useful, but most people are probably not going to do that. You're not going to be a weirdo like me and buy your own frigging metabolic heart to do your own testing, but just non invasive way of doing that and have that measurement give you feedback while you're doing it, I think would be super useful.
Simon Wegerif: Yeah, I totally agree with that. And seeing that progress over time with your training can help to reinforce the, you know, the good discipline that's required to do the Zone 2 training efficiently.
Dr Mike T Nelson: Yeah, and it could just give you simple, you
Simon Wegerif: go over the line, right? I mean, you, you need to do, need to do lots of volume just, just below the line.
Dr Mike T Nelson: Yep. And I think it would just give you simple metrics of [01:07:00] percentage of time, you know, in zone two, you know, percentage, you went over your total duration in the zone, and then you know, your average heart rate in the zone over time, right? So now you can confirm you were doing true zone two training.
You know, 95 percent of the time, Ooh, my average heart rate before for 60 minutes was 117 beats per minute. You know, now eight weeks later, it's 113 beats per minute or whatever. Right. You can, cause I think that's the hard part with zone two is that, yeah, you can look at power output and stuff like that, but most people don't have a lot of those complex metrics on their bike.
So now you can take very simple stuff and see progress actually over time, which I think is always the hardest for like the zone to work. No, I would agree with that.
Simon Wegerif: But it's a really good investment in your body. You know, I think one of the reasons why I recovered quite well after surgery is that I'd just done so many hours of zone two in the bank and, you know, that gives you, hopefully it gives you [01:08:00] some good metabolic efficiency and flexibility and that can serve you well when you need it later on.
Dr Mike T Nelson: Yeah, the last question that you brought up zone two real quick is do you think you should do zone two stuff? Fasted and if someone let's say argue is really in zone two What about duration like what are your thoughts on? Duration they should be trying to hit per week. Hmm
Simon Wegerif: Well, I asked a question pretty similar to that at the science and cycling conference, which a lot of the top coaches go Oh, yeah Yeah, the couple of days before the actual Tour de France.
Oh, nice. And that was in the time when, you know sort of keto exercise was, was being talked about a lot. And I basically, you know, asked that a similar question. And and I got, I got shot down rather heavily. Really? Yeah, I did. Yeah. Why? Well, the, the, You know, they thought it really didn't make [01:09:00] much sense to, to do zone two training fasted.
But I suspect that, that was in the context of high training volumes and wanting to ensure that the athletes can do those, I mean, it's, it's like in Chris Froome's case was like six to eight hours of zone two training day after day, right?
Dr Mike T Nelson: Yeah, because all those high level cyclists are psychos. They
Simon Wegerif: are.
They are. They
Dr Mike T Nelson: are! They
Simon Wegerif: are. They are. So, yeah. I don't know. It's certainly something that I've done a bit of. I know that if I go out fasted in the morning, doesn't matter what I've eaten the night before that at pretty much exactly 90 minutes, my performance will fall off a cliff. So that's, that's, and that hasn't changed much over the years, to be honest.
Interesting. Yeah. But I don't know. What are your thoughts?
Dr Mike T Nelson: The short answer is I really want to see a study done because a lot of the [01:10:00] data, you know, from like San Diego Milan, who's done a lot of awesome work. Like I love his stuff. He was testing that shit. I used to send people to have metabolic flexibility testing in his lab, freaking 12 years ago.
He's the only person who was like, yeah, that sounds like a good idea and was actually testing people. But so I love all this stuff, but. A lot of, I think there's an over interpretation of Zone 2 data from high end cyclists. And is it beneficial in that population? I think of course it is. But I want to see a study in high end cyclists where maybe they did only 6 hours of Zone 2 and one other group did 2 hours of Zone 2.
Was there any difference? Because you know, working with high level cyclists, the only way to get them to not do high intensity stuff is to tell them to do zone two stuff because left to their own devices, like all their, they're just going to err on the high end all the time, at least in my limited experience.
So by having them do zone two, you're actually titrating down the mile of high intensity work they can do on purpose. And I'd love to see that compared to [01:11:00] bro, just go for a walk or something, which again. High end cyclists are never going to do this study. I don't even know if it'll ever get done. But my guess is, the high numbers of hours Zone 2 has done in that group is beneficial because they're not doing high intensity stuff.
Now if you take someone who's not very well trained, their VO2 max is barely 30, telling them to do 3 hours or 4 hours of Zone 2, I think there's benefit to it, but I don't know if that's That's the best starting point because there's such poor leverage. I think if you've hit a plateau, you're in the middle, your VO2 max is maybe a high forties, low fifties.
You've done all the intelligent training and you can't get past a certain point. Then yes, I have had those people go back, do two, three hours of zone two stuff, do it faster, do it for eight hours religiously. Now we'll start adding back VO2 max work and high intensity stuff. And then they seem to be able to handle that volume better.
I don't know. That's my bias right now.
Simon Wegerif: Yeah, no, that [01:12:00] sounds sensible to me. And I think for time crunched athletes that want to do some zone two, but they also want to get some intensity in, I think it was, and he goes to my line that said, you know, if you're doing like a, an hour and a half workout, then do, you know, the first Yeah, 80 minutes or so in well controlled in zone two, then really go for it the last 10 minutes of the ride, you can still like, you know, you could you can pack something off higher intensity in right at the end.
I've also got a friend I rode with last weekend who'd recently been on a, on a training camp with pro cyclists and he said he was amazed at just how polarized. The, the training regime they'd been under was it was hours and hours of zone two, and then they'd be, they'd do like six 32nd sprints, you know, all out sprints at an incredibly high intensity, you know, like a thousand Watts or so.
Yeah. Just
Dr Mike T Nelson: insane output.
Simon Wegerif: Yeah, but for very short periods of time, very, very, very well controlled.
Dr Mike T Nelson: Yeah. Yeah, no, that's [01:13:00] good. I, I don't know. Cause I always get lots of hate mail about zone to yay or nay. It just seems like the group that's saying they need more zone to training. At least in the fitness world, from my biased opinion is the group that I probably would not have do zone two training.
The group that's already doing it, the high end athletes, they've already been doing it. They've been doing it for tons of years. It's just such a hard sell to get someone who's not doing any aerobic training. To be like, bro, I want you on a bike for three hours this week. They're like, screw you. What are you talking about?
And again, if their VO2 max is like 30, I just don't think that's the best use of their time to start. I don't think it's bad. I just think that's a really hard sell because you don't really see a big output at the end of that eight weeks either. And
Simon Wegerif: that's a mistake I made. You could be going really slowly as well.
You're not, you're not going to, it's not going to be a very exciting journey if you're, if you're. Oh no. If you've only got like 30 mils per kilogram per minute. Yeah.
Dr Mike T Nelson: Yeah. [01:14:00] Awesome. Well, where can people find out more about you if you want to be found and tell us about the new company and everything else?
Simon Wegerif: Yeah, well, I mean, I'm on, I'm on LinkedIn Simon Weger from LinkedIn and the, I think website is, is still up as well. So if anybody wants to email me directly, it's simon at myathlete. com. So yeah, look forward to that. I've really enjoyed, really enjoyed catching up. It's been great.
Yeah. Thank you so much for being on here.
And thank you so much for, you know, all your work over the years and especially for. Developing the app because I mean, it being able to measure HRV daily with clients, especially starting back 14 years ago, that was a. A huge game changer, because when doing it in the lab within that short period of time, I didn't foresee that we would be able to do it at home at a reasonable cost.
I mean, there were some other systems like a mega wave who did a good job, but the cost was just out of range for, you know, 99 percent of people. So to have it be inexpensive and something they can do at home [01:15:00] in a short period of time and accurate, that was, that was like actually a true game changer, which I know that phrase gets overused, but that actually was.
Simon Wegerif: Yeah, no, I'm, I'm, I'm pretty happy with what we did. Didn't, didn't get mega rich out of it, but hopefully hopefully helped a few people to understand their bodies a bit better. Yeah.
Dr Mike T Nelson: Awesome. Well, thank you so much. I really appreciate it. All right.
Simon Wegerif: Cheers, Mike.
Dr Mike T Nelson: Thank you.
Thank you so much for listening to the podcast here. I really appreciate it. A big thanks to Simon for all the support over many, many years. Being the first person to put out an app for heart rate variability that I've been using with my private online clients literally for 14 years straight. I do some work with heart rate variability, a little bit with the guys over at Rapid Health Optimization.
Primarily using Aura for that and also primarily looking at sleep. So I do a sleep analysis on all of the clients that come through their way. And yeah. So huge thanks to Simon. [01:16:00] Hope you enjoyed the discussion. If you want more super geeky information, make sure to sign up to my daily newsletter, which is free.
You can go to the link down below here and you'll be able to get on it and just say hi. I'll send you a free gift also if you do that. So just hit reply once you're on there. And then we've got the Heart Rate Variability Education course. We'll put a link to that down below if you really want to take a deep dive on heart rate variability without having to go back to get an engineering or a mathematics degree.
No need necessary. And then when you're in the course, you can actually email me if you have any particular questions. I'm more than happy to help you out there. And if you're looking for other things to test, check out my friends at Element for electrolytes. And then also tecton for ketone esters that are tasty.
So thank you so much for listening to the podcast. Really, really appreciate it. And as always, if you find someone who may enjoy this podcast, please [01:17:00] forward it to them. And appreciate all of you hit the link, subscribe, download all that kind of cool stuff to help the old algorithms. Thank you so much. We really appreciate it.
Talk to all of you next week.
I wish they had done that differently. How would you want them to do it? Better.
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