Today we’re looking at HRV- endurance training, adrenal fatigue, and future app developments.

If you didn’t listen to it, in Episode 1 we primarily looked at resistance training, or weight training.

Today we also look at some scenarios where the HRV metric can be confounded where an increase in it is not good, how it can be used to identify possible adrenal fatigue and how to improve its accuracy by combining it with Resting Heart Rate and qualitative measures.

Today’s guest is Simon Wegerif who founded ithlete, the first HRV app company, which appeared 5 years ago in 2009. In comparison to Andrew Flatt, whose focus was resistance training, Simon has a background in primarily endurance training and it was for this he originally became interested in HRV.

Since 2009, through working with its client base including a range of pro and amateur athletes and everyday gym goers, and now universities in connection with studies, ithlete has evolved its app to cater for specific scenarios like adrenal fatigue and understanding how individual factors are impacting training. Simon has been diligent in staying up to date with the research and adapting the ithlete app to take advantage of it as it evolves.

The show notes, biomarkers, and links to the apps, devices and labs and everything else mentioned are below. Enjoy the show and let me know what you think in the comments!

itunes quantified body

Show Notes

  • The status of research on Heart Rate Variability and some of the issues to overcome such as standardisation.
  • HRV as a predictor of endurance performance – now as effective as running times?
  • Using “Active Recovery” to recover quicker from endurance and resistance training.
  • True overtraining vs. non-functional overreaching – how to improve training results by understanding how HRV indicates these two .
  • How to diagnose potential adrenal fatigue with a combination of HRV and RHR (resting heart rate) metrics.
  • The one situation where you don’t want your parasympathetic to become dominant (or your HRV to be high).
  • The need for HRV benchmarks to be established in order to compare your “health future” to others and as a proxy for aging.
  • The Palo Alto Prize spurring on new investment in research to improving longevity based on using HRV as a feedback mechanism for experiments.
  • Using yoga breathing (Pranayama) to increase Heart Rate Variability by up to 5 points within a few days.
  • The biomarkers Simon tracks on a routine basis to monitor and improve his health, longevity and performance.
  • Simon’s one biggest recommendation on using body data to improve your health, longevity and performance.

Give some love to Simon on Twitter to thank him for this interview.
Click Here to let him know you enjoyed the show!

The Tracking


  • Heart Rate Variability (HRV): Measures how your heart rate varies over time. Research studies link HRV to recovery status, stress and other aspects of human physiology.
  • Resting Heart Rate (RHR): Measure of your heart rate at rest (typically measured upon waking).
  • Calories: We discussed the merits of measuring calories in and out, the current hype cycle around ‘calorie counting’ apps and devices, and its relationship with weightloss.

Apps and Devices

  • ithlete HRV App: The app Simon developed which includes some of the RHR and adrenal fatigue functionality discussed during this episode.
  • Polar H7 Bluetooth Smart Heart Rate Sensor: A chest strap heart rate sensor that works with the ithlete and other HRV apps (Damien uses this one).

Simon Wegerif and ithlete

  • ithlete: Simon’s company and the HRV app with the same name.
  • You can also connect with Simon on twitter @SimonWegerif.

Other People, Books and Resources



Full Interview Transcript

Transcript - Click Here to Read
[Damien Blenkinsopp]: Hi, Simon. Thank you very much for making time today to come on the show.

[Simon Wegerif]: No problem, Damien. Really good to talk to you.

[Damien Blenkinsopp]: What I thought we would first do is quickly, where does ithlete fit in with the world of HRV apps and development, from your perspective?

[Simon Wegerif]: Okay, well, ithlete was the first HRV app available, and when I first started getting really interested in HRV, which was early 2009, I decided it was so interesting to me as an engineer by background, but also a keen recreational endurance athlete, trying to make the most of my own somewhat limited abilities, that the iPhone was just being launched early in 2009, and talking to a couple of people, I was looking for ways to realize my hopeful invention of a convenient, simple-to-use, but accurate HRV measuring device. And people said, you know, why don’t you do it as an app in the iPhone? So I started thinking about that, and I made that my target during 2009, and got the prototypes all done on an iPod Touch, and at that time, I think it was IOS version 2 was just coming out, so we were easily the first to bring even accurate heart rate measurement onto the iPhone, let alone HRV. So we’ve been doing this for a little while now, and the product, I think the current version of the app is relatively mature because of that.

It’s also — being the first gives you some advantages in the early — doctors in research started looking at it quite early on, and we’ve now got some good quality validation studies that have been done that show, in fact, the ithlete measurement to have an almost perfect correlation with the gold standard of ECG, which we’re very happy about. The ithlete finger sensor has also been validated.

[Damien Blenkinsopp]: Great, great. Well, you have three sensors. You’re using the finger sensor, the Bluetooth heart rate chest straps, and isn’t there another one?

[Simon Wegerif]: Yeah, the other one was actually the original one, Damien, so in the early days of the iPhone, there wasn’t any convenient and reliable way of getting a heart rate signal into the phone, so I designed a little adapter, a plug-in adapter which would go into the headset socket, which I still think was a good choice, because headset sockets are available, you know, on pretty much every phone, and the way they’re connected has remained standard, now, for three or four years. So it’s a little device which users can take from one phone to the next, be that iPhone, Android, or even Windows phones, if we do an app version for that. And that little receiver picks up the signal from the Polar type of chest strap, and, of course, that Polar transmission system has been around since the early 1980s, so there’s an awful lot of products in the market that support that.

In fact, although Bluetooth [Smarties 00:05:56] is, in many ways, the state of the art, and the finger sensor is the most convenient, we still sell a lot of the — what we call the little ECG receivers because of the massive installed base of Polar type straps and systems.

[Damien Blenkinsopp]: Okay, great. So I know you stay up-to-date with the research, and you’ve been following this since 2009 or before, so could you give us a bit of an overview, from your perspective, of the research? How much is there related to HRV? Where are the strongest areas, and, you know, how you look at it?

[Simon Wegerif]: Yeah, I think if you were to put heart rate variability into PubMed, which is the — you know, the recognized research database of peer-reviewed papers, I think you’d probably get about 14,000 hits. So there’s an awful lot of peer-reviewed research which has been done on HRV.

[Damien Blenkinsopp]: Do you mean 14,000 papers, separate papers?

[Simon Wegerif]: Yes, 14,000 separate papers, yeah.

[Damien Blenkinsopp]: Great, great.

[Simon Wegerif]: Which is quite a high volume. A lot of that is focused on disease state, so looking at autonomic dysfunction, for instance, in diabetes, cardiovascular diseases, cancer, and a lot of other disease states like that, but there is a fair body of research studies on sports performance and health as well. During my preparation for designing the ithlete app, I read about 500 papers during 2009, and I’ve now got about 1,000 in the collection, my collection that I’ve read.

Some of the papers have got some strikingly good methodologies and breakthroughs, and others are a bit weaker. I think one of areas where heart rate variability research has not done itself any favors is not standardizing in units or protocols. For instance, things like the duration of the measurement, the units that are going to be used, the position of the subjects, whether they’re lying down, walking around, standing, sitting, what are they doing. There hasn’t been much standardization there, I think partly because a standards document was never adopted in the industry.

[Damien Blenkinsopp]: So one thing I noticed about your ithlete app when I was playing around with it was that when you’re taking the reading, it’s got the breathing timer. It’s got this circle that moves up, in and out, with your breathing, which I thought was great to try and standardize that aspect a bit better in terms of how you’re breathing and just keep more rhythmic and controlled every time you’re doing it, instead of different. Is that why you put it in there, or?

[Simon Wegerif]: Yes. Breathing has a very important impact on heart rate variability, so when we talk about HRV, particularly in sports performance and everyday health use, we nearly always mean parasympathetic HRV, and parasympathetic HRV is primarily dependent on breathing. In fact, the HRV is caused as part of the breathing feedback loop with the brain. So as you breathe in, your heart rate gets faster; as you breathe out, your heart rate gets slower. And it always seemed to me, as an engineer, that unless you’re controlling your breathing in some way, that your HRV measurement process is going to be somewhat unpredictable, if you’re just relying on a breathing pattern which is uncontrolled. So controlling that breathing, but without creating stress, hopefully, in the user is the objective here, because everyone who knows much about HRV will know that stress lowers your HRV. So we don’t want to stress the person during the measurement, but we do want them to have a constant breathing pattern, and hopefully the ithlete breathing pattern is something that’s evolved over three generations of the app now, and we hope that people find it peaceful and relaxing to use.

[Damien Blenkinsopp]: Yeah, it’s kind of like this pulsing heart thing. I found it relaxing, and it’s just nice to have an indicator. Because I’ve used other apps, and, you know, they don’t have that. So every time you’re probably breathing a little bit differently, but you don’t notice it. So I thought it was a nice touch. Thanks for that overview.

So, you’ve done a lot of work in the endurance and aerobic areas. We haven’t looked at that yet on the show, so that’s what I’d like to explore a bit more with you. Any idiosyncrasies or differences compared to weight training, which we’ve looked at quite a lot with Andrew Flatt in the past. How would you say that it differs from weight training in the way HRV relates to endurance?

[Simon Wegerif]: Well, one thing, as a segue or a link from the body of research on HRV, Damien, is that a lot of the studies in the sports performance area have actually been done with endurance sports. So they’ve been done with running, cycling, rowing, cross country skiing, because, of course, Finland and the Nordic area has been one that has done a lot of adoption and research into HRV. So there is — the body of research in endurance sports is strong. It’s also something that I’ve been personally interested in, because one of the reasons I created the app originally was to improve my own performance, originally, in triathlon, but lately in long distance cycling.

And so HRV, interestingly, has been something which is really quite well proven and quite well applied to endurance sports. And one of the things about some of the research that’s come out in the past couple of years has been the very good correlations between changes in HRV and changes in performance. So there have been studies done at the national level on French swimmers where they measured their HRV before doing a weekly 400-meter pool time trial, and they found the correlation was so good between the individual’s change in HRV and their variation in performance on the Thursday time trial, that they said one or the other is good enough here. So if we measure their HRV, they don’t need to do the weekly time trial to assess performance improvement.

And a key researcher in this field also, Martin Buchheit, also found when club runners were training to improve their performance in 10K races, that only the runners that improved their HRV during — I think it was an 8-week training program. Only the ones that improved their HRV, improved their running times. The ones whose HRV didn’t improve, their running times didn’t improve, either.

So there’s been some very clear findings in the endurance area. And I think training guided by HRV is becoming more and more practical for endurance sports as a way of maximizing performance with the training time that’s available, but without risking overtraining.

[Damien Blenkinsopp]: Right, right. I know with respect to endurance, we’ve touched on this a bit with Andrew Flatt, he was talking about basically how he would be doing weight training, and his HRV would go down, but if he did a bit of aerobic as well, he would limit how far his HRV would drop the next day. How do you explain that? What’s going on there?

[Simon Wegerif]: Yeah, there’s been a pretty important study that came out, I think it was late last year from a couple of researchers in the University of Queensland in Australia, and again with Martin Buchheit involved, that built on work done by researcher Stephen Seiler, who’s been looking at the way, for instance, marathon, long distance runners have trained in Kenya for many years. And what he observed there is that they tend to follow a polarized approach to training. So the majority of their volume, say 80% of their training time, is conducted at what appears, to many athletes and coaches, to be really quite moderate paces, fully aerobic work. And in fact precisely defined, it’s a level of aerobic work below the first lactate threshold.

So essentially the lactate level in the blood is close to the athlete’s ordinary baseline. And recovery from that kind of aerobic work, although athletes can do habitually quite high volumes of that, you know, many hours a week, is very quick. And that’s reflected in HRV. But when you go above that threshold, then recovery takes much longer to achieve.

So in Andrew’s case, I think what he’s really enforcing is the fact that aerobic exercise really allows rapid recovery, and the fact that the metabolism is accelerated is helping to process the byproducts from the high intensity sessions and perform, essentially, what we call active recovery. Active recovery actually gets you back to baseline more quickly.

[Damien Blenkinsopp]: Does that reduce the stress, the stimulus to improve your body in any way? We’ve also spoken to, like, Doug McGuff of Body By Science. He talks about inroads, so, you know, one of the things about heavy weight training is you want to create a large enough stimulus to improve strength. So is this in any way — it sounds like it’s reducing, in a way, the stressor. Is that a correct way to look at it? I’m just wondering if that has an impact on how your body tries to compensate.

[Simon Wegerif]: Yeah, it does seem to be having that effect by stimulating the parasympathetic nervous system. And the parasympathetic nervous system is good for reducing inflammation, for rebuilding energy stores, glycogen in the liver, for ensuring that oxidative stress is reduced. And the really useful thing about long slow distance or aerobic training in endurance athletes is that it provides a good level of stimulus for mitochondria to adapt. So one of the things you want as an endurance athlete is an efficient metabolism with lots of mitochondria in the muscles, which are able to process fuels and turn those into energy. And what you also want is a metabolism that’s able to use fats as fuels. You know, your store of fats in any body, even thin people, is many, many thousands of calories, and fat is a very efficient way to store fuel. You know, it’s 9 calories per gram. Whereas, carbohydrate is 4.2 calories per gram, and carbohydrate is usually associated with quite a lot of water retained in the body as well. So if you can use fats as fuels, that’s a big advantage.

If you’re running a marathon, then you’ve only got enough glycogen for about — you’ve probably got about 800 grams. You know, you’ve probably got — your total body store is about 3,000 calories, of which your body will probably only allow you to use a couple of thousand, so your ability to supplement that glycogen fuel with fat stores is something that your body learns to do and learns to adapt to when you spend time training aerobically.

[Damien Blenkinsopp]: Yeah, we discussed this with Jimmy Moore. He’s done a lot of work with other people in keto diets and so on involved with training. So, yeah, it’s good for you to make that connection and bring that up in this context.

Okay, so kind of round off the impact — so you’re saying it helps recovery — it helps accelerate recovery by stimulating the parasympathetic system.

[Simon Wegerif]: That’s right, as well as building — building the cardiovascular system and energy stores and energy system to make you — make you efficient, really, and be able to go for a long time.

[Damien Blenkinsopp]: Are there any cases where we shouldn’t be doing this? If we’re just focused on HRV, it’s like, oh, well, it leads to a higher HRV, so — if we’re always just aiming to increase the HRV, which is part of the discussion I wanted to have today, so should we always be doing that? So if we’re weight training and we can do a little bit of aerobic to increase our HRV, so everyone be doing this?

[Simon Wegerif]: I think everybody should be doing a certain amount of it, but it’s not going to lead to good race pace performance unless it’s also complimented by some high intensity stuff. And the general adaptation syndrome of Selye, which was, you know, written a very long time ago, basically talks about stressing the system and then allowing time for it to recover, and when it recovers, it supercompensates, so the body is stronger than it was before. And high intensity work is a very good way of stressing the body sufficiently that it is stimulated to adapt and supercompensate compared to where it was before. And that’s a necessary component of high performance athletics.

[Damien Blenkinsopp]: Okay, okay. So it sounds like everyone — although it’s not going to lead to a higher baseline, by the sounds of it. If we think of we’re trying to increase our HRV over time in terms of kind of aggregate, rather than the ups and down adjustment cycle of just trying to time our training properly, doing a little bit of aerobic with our strength training probably isn’t going to increase the baseline. It just may help us to get back to another workout sooner than later in terms of recovering quicker. Is that a fair assumption?

[Simon Wegerif]: Yeah.

[Damien Blenkinsopp]: Or would that be, actually, kind of biasing the result, and it would be better to — I guess this area isn’t 100% clear as yet.

[Simon Wegerif]: It isn’t 100% clear. I’m trying to recall my own experience of doing a lot — because I’ve prepared for a pretty long cycling event across the Alps this summer, and I did a lot of hours of fully aerobic training, so I was very careful to keep my heart rate and intensity level below the first lactate threshold, and I accumulated a lot of hours, basically, about 15, 17 hours a week for about four or five weeks of this. I didn’t actually see my HRV baseline rise much. What I did notice was my resting heart rate went down during that period, though, and that was a very clear trend.

[Damien Blenkinsopp]: Okay, so let’s talk about that, because I know that’s something very important to ithlete. You track the HR, the resting heart rate, as well, and you use that in your assessment. And you see it as an important part. So what is the HR for you? What is it doing in terms of tracking and helping you to understand performance and recovery and so on?

[Simon Wegerif]: Well, resting heart rate, most people who do training and even people who know about health would recognize that a lower heart rate — a lower resting heart rate is very often a good thing. And most of the time, that it true, because it’s actually the ratio of your maximum heart rate to your resting heart rate that determines your VO2 max. So there is, for instance, a ready reckoner for VO2 max, which is your maximum heart rate divided by your resting heart rate times 15. So, you know, as your resting heart rate decreases, provided your maximum heart rate stays the same or only decreases a very little bit, then your VO2 max will increase.

Now, there are also situations, which can be due to either non-functional overreaching, so some states of overtraining, or even —

[Damien Blenkinsopp]: When we say non-functional overreaching, what does that mean?

[Simon Wegerif]: Well, non-functional overreaching is basically what you might think of as the third stage in progression of training load and recovery imbalance. So the first stage is shock, also known as the alarm stage, which is the body’s healthy response to a new stressor. And during that stage — so you do something intensive, your body is temporarily stressed. It reacts with an increased sympathetic tone, increased output of central stress hormones, increased adrenaline, norepinephrine, cortisol, and if you then allow time for the body to recover, then it supercompensates, and you actually end up you are a little bit fitter than you were before the stressor had been applied.

Now, overreaching is a deliberate imbalance of training and recovery, usually over a short period of time within a periodized block. So a lot of endurance training programs are periodized into a month or a 5-week block whereby you have a progressive overload, then, you know, ending up with a taper or a recovery week. And that is called functional overreaching, because you deliberately continue to stress the body, and then in the last week, you taper, and you supercompensate, and, you know, the benefits of training are imbedded in your system.

If the balance of training and recovery is such that, you know, your body really — it can’t cope with the amount of load that’s being applied, and that can include environmental conditions as well, so that can include bad diet, lack of sleep, all these other things which are, in fact, stressors to your body as well as training, then if, you know, after a short taper period you don’t recover and supercompensate, but you stay in the hole, as it were, then that’s non-functional overreach.

[Damien Blenkinsopp]: Uh-huh, okay.

[Simon Wegerif]: But people do even go beyond that. It is — yes, it is really — the way I would define non-functional overreaching is that when you take the training load away, you don’t see recovery or supercompensation within a few days or a week.

[Damien Blenkinsopp]: And does it take much longer, or would you have potentially basically lowered your baseline by overstressing the body?

[Simon Wegerif]: Yeah, and it can take weeks to recover from non-functional overreaching. And non-functional overreaching is still not as bad as true overtraining. True overtraining is really quite a serious condition, and it’s not that common, but it can takes months or even years to recover from. It can —

[Damien Blenkinsopp]: How would you differentiate the two?

[Simon Wegerif]: Yeah, true overtraining, again, is an extension of the states of overreaching, whereby you take away the training altogether, and the individual really remains in a chronically stressed state. I think it is quite rare, although certainly we’ve been contacted on a number of occasions by athletes and coaches who know that they are overtrained. And this is also known as the exhaustion phase in the General Adaptation Syndrome. And the body is basically continually failing to adapt to the chronic stress. And the chronic stress also starts to burn out the adrenal system, so the central nervous system starts to shut down production of central stress hormones. The adrenal glands themselves desensitize.

A sympathetic response is normally quite healthy.You know, when a person needs to have a fight or flight response, they want to be able to turn it on and turn it off again quickly. When somebody’s overtrained, that response is pretty much absent, to be honest.

[Damien Blenkinsopp]: Right. We talk a lot about the importance of parasympathetic. In one of our previous interviews, we talked about the fact that most people are sympathetic dominant, mostly because of lifestyle reasons today, and so on. So in the HRV Sense app, for instance, Ronda Collier, she noted that most people have a very high sympathetic in their LF, and their HF tends to be much lower. And over time, they can, you know, look at that for stress and so on. But now we’re talking about also that overdominance of parasympathetic can be a problem? Is that associated with adrenal fatigue?

[Simon Wegerif]: Yes, indeed. Once the body gets itself into this state whereby the sympathetic response is essentially impaired, then — it’s interesting. I mean, that’s a pretty bad state, right? I mean, that’s also a state where protein synthesis becomes impaired, so, you know, muscle damage becomes much more likely. Decreased testosterone and other anabolic markers, increased baseline cortisol, so basically, you know, the body is in quite a stressed state, although it’s sensitivity to the adrenal family of hormones has been reduced. And then, you know, parasympathetic becomes essentially dominant. You swing to a high HRV, which if you weren’t looking at heart rate, you might say that that’s a good state, right?

[Damien Blenkinsopp]: Right, right, right. So let’s be clear. What would the heart rate be doing that’s different to show that this is a negative HRV despite the fact that it’s high?

[Simon Wegerif]: Yeah, so what actually happens is that the resting heart rate decreases pretty significantly compared to your normal range. So all of the ithlete measures are based on solid statistics and smallest worthwhile change and things like that, so we’re always tracking rolling means and rolling standard deviations. We can look at the heart rate and see if that all of a sudden — you know, if that over a short period of time goes much lower than it should do normally, and coupled together with an unusually high HRV, then that is quite characteristic of parasympathetic dominant sympathetic burn out state.

[Damien Blenkinsopp]: Right, right. Have you come across many cases of this?

[Simon Wegerif]: Yeah, I’ve certainly see it in myself. We first came across it, because it’s not that well documented, so most of the textbook stuff on overtraining tends to talk about sympathetic dominance, and indeed that is the case through functional and non-functional overreaching. But then, you know, when people keep going, and there are some very motivated type A individuals that keep on going, and they get themselves further into this — into this truly overtrained state, the first time we —

[Damien Blenkinsopp]: Right. So would it be correct to say that your HRV would go down for a while, and if you ignore that, then you might get to this situation?

[Simon Wegerif]: Yes, absolutely. That is exactly what we see.

[Damien Blenkinsopp]: Right, right.

[Simon Wegerif]: The first time we noticed this, in fact, was in the beta testing of the original ithlete app in 2009, when we gave it to a national standard runner and triathlete, and he did a three-day running event in Southern England over the South Downs, and he said, ‘Hey, you know what, guys? My HRV was really high this morning, and I’m completely knackered. You know, what’s going on?’ And we started to look into it and talking to some researchers and developed this test, basically, out of that.

And we certainly have seen it a few — you know, a few times. I’ve seen it a couple of times myself. In fact, the day after I finished the Haute Route Alps, which was 1,000 kilometers in seven days across the Alps, I was six hours a day on the bike working quite hard, the day after that, the Sunday, my HRV all of a sudden swung from low, which had been progressively decreasing during the week, and it swung very high, associated with a much lower than normal resting heart rate, and ithlete went — gave me a straight red.

[Damien Blenkinsopp]: Right.

[Simon Wegerif]: So ithlete doesn’t mess about in that situation. It gives your a red card straight away.

[Damien Blenkinsopp]: It’s nice that it does that, ‘cause, you know, often I imagine most of the apps don’t pick that up, that scenario. So in terms of a swing of HRV, do you remember your — just to give people an idea, where did it kind of start from baseline, and it lowered steadily to what, and then it jumped up one day?

[Simon Wegerif]: Yeah, I can’t remember the numbers right now. I did do a blog post about it, in fact, so it’s on — yeah,, I did a blog post about my HRV before, during and after this actual event. I think you can go look at that.

[Damien Blenkinsopp]: That’s good. So we’ll put a link in the show notes to help people. Okay, so this final thing on adrenal fatigue, is adrenal fatigue is a widely discussed topic today, because a lot of people, not just people who are training, but often it’s the weekend warriors, the people who are working during the week, and they got out and have pretty stressful jobs, and then they’re training at the weekends, or they’re doing triathletics and all these other things at the weekends. And there’s this question of when they start getting more and more tired is the adrenal fatigue. Doctors and clinicians argue about this and how to test for it. And many of the tests are considered not ideally accurate, there is saliva test, there is blood tests, and there’s a bit of discussion there. So I’m just wondering whether you think this would be a relevant biomarker, and if you’ve seen anyone try to compare it to some of those other adrenal fatigue tests?

[Simon Wegerif]: I haven’t. A practical test I could recommend for people, though, is if you suspect you might be starting to get adrenal fatigue, then the likelihood is that you won’t be able to manage high intensity exercise. You know, you simply — you hear comments like, ‘I was unable to get my heart rate or my power up into the right zone.’ You will notice that. And it is literally impossible. You just cannot manage the effort levels, no matter how hard you try. So your perceived exertion would go right up, but your metabolism and your body wouldn’t respond to the workload and energy levels that are required.

[Damien Blenkinsopp]: Yeah, yeah. So I noticed, also, that when you were talking about how to notice this, you know, you spoke about an athlete who came to you and said, ‘Look, my HRV’s really high, but I’m feeling terrible. I’m feeling really tired.’ So in ithlete, you have a bunch of indicators that you track whenever you track your HRV for training, in the morning you have sleep, fatigue, muscle, and stress, and mood, and diet. Do these filter into some kind of algorithm, or how are you using these to help people make decisions?

[Simon Wegerif]: They are going to. I mean, at the moment, these are quite widely used subjective metrics, and they are quite useful for tracking overall health and wellness, as well. So at the moment, it’s great for people to record those every morning, and on the ithlete, if they rotate the dashboard around to the landscape chart, they can visually for themselves see correlations between any one of those variables and their HRV, and in my case, I’m really not very good, if I’m lacking sleep, quality or quantity. So, you know, my HRV normally shows quite a good relationship with my sleep score. Other people —

[Damien Blenkinsopp]: Right. Is that the same for everyone, or do people have different weaknesses? You know, the high leverage weakness you’ve got to kind of avoid. So yours is sleep. Mine is probably sleep, too.

[Simon Wegerif]: No, I think people absolutely do have individual characteristics there. It could be stress for some people, or it could be diet in others, if they have particular dietary sensitivities. But what we are just starting to do, right now, in fact, is a cooperation with a UK university on some advanced statistical algorithms which will look for relationships between those individual subjective variables and the HRV over a period of time. So what we hope to be able to do within the next six to eight months or so is to be able to give users feedback and insight into their own data.

I — you know, for me, HRV has always been a journey of personal discovery. I’ve found out things about myself, what my body and my brain likes as assessed by HRV, and, you know, I’ve been able to keep my HRV sort of steadily trending upwards over the five years that I’ve been doing this; whereas, normally it would decline with age. But, yeah, what we want — what we aim to be able to do is to give users insights, exactly as you say, Damien, telling people, you know, over the past month, sleep was the most important factor for you, perhaps again, and diet was the second, and it seems like you’ve been having a lot of stress recently, and that’s been affecting you as well.

So I think there’s potential for this to go quite a long way, including things like, perhaps, looking at all the relationships between everything people are capturing, and then saying with some statistical confidence all of this stuff that you’re capturing isn’t explaining all the variation we’re seeing in your HRV, is there something else? Is there, for instance, travel?

You know, one of our — one of the members of our team just noticed that driving for periods above three hours was causing a big drop in his HRV the next day. So potentially we can also alert people to things that they’re not capturing or not trying to understand right now, but which nonetheless are affecting their health.

[Damien Blenkinsopp]: Yeah, yeah. So, yeah, just to be clear, because I didn’t bring this up before, but these ratings you enter into your app are basically from, you say sleep quality, and you just give a rating from weak — it’s kind of like 0 to 10, right?

[Simon Wegerif]: Yes.

[Damien Blenkinsopp]: Or you can put very strong, and that’s for each of them. So they’re qualitative measures, but as you say, you’re finding correlations with them, and you’re going to be looking into more of that.

[Simon Wegerif]: Yeah. We turn the position of the slider into a number, like you say, between 1 to 10, and I think that’s a technique — I think that’s called a visual analogue scale or something like that, and the statistics will be using those numbers to determine relations and give people feedback.

[Damien Blenkinsopp]: Right, great. Well, [00:35:23] we’ve explore a bunch of new topics and interesting scenarios that we hadn’t come up with before, because you’ve got this user base which is using ithlete. I think what would be interesting is, like, what do you see people mostly using this for, and what are the kind of biggest use cases, and most useful things people are using it for?

[Simon Wegerif]: We’ve got a wide variety of users. We’ve got well over 10,000 users now on the ithlete app, and they really vary. They do vary from weekend warriors to — all the way through to top professional athletes, both in team sports, endurance sports, things like boxing as well, through to health and wellness practitioners. So we certainly get quite a few bulk orders from chiropractors and holistic wellness practitioners and people like that. And I think it’s used for all kinds of things. It’s used by health conscious people who just think HRV is a good metric to track every day, and, of course, it is. It’s a sort of holistic measure of adaptation reserves or overall well being. So it’s a great thing for people to track.

I think in the more serious side of sports, people are looking in their training not to have dug themselves into too much of a hole, and they fairly quickly start to take the tool seriously when they get amber and red warnings, and they still go training on those days. They fairly quickly work out that that’s a bad idea, and they start to trust the tool more. We give them feedback on a day-to-day basis.

[Damien Blenkinsopp]: Is there any scenario where you wouldn’t trust it? I mean, we’ve highlighted one that you’ve identified and you’ve integrated now into ithlete, with that one HRV going up. Is there anything else you’ve kind of got on the horizon? Maybe there’s a couple of other scenarios that need to be looked into?

[Simon Wegerif]: Yes, definitely. One of those is taking readings at an unusual time. So the ithlete algorithms are based on you doing things at the same time every day. Ideally, it should be first thing in the morning, because then you haven’t got additional variables of drinking a coffee or not, or having something to eat, or looking at — opening emails, having an argument, anything like that. Those variabilities all eliminate it. And, of course, another advantage of doing it first thing in the morning is that you can plan the day ahead. So, you know, darn, I got an amber instead of a green, but it’s not too late, I can modify my training or something else that I was going to do today.

[Damien Blenkinsopp]: Yeah, that’s interesting, because in a future episode, I want to have someone talk about willpower, because I’ve read a fair amount about the correlation between HRV and willpower, and, you know, basically motivation and drive. So if I have a low HRV one day, I’m, like, okay, I’m going to take on less and less business tasks today. I’m going to focus maybe on one instead of trying to get five done. I kind of factor in like that. I mean, obviously you’re feeling like that as well, but I’m also kind of aware that maybe I need a recovery day in terms of just taking on work stressors and mental stressors and things like that, in order to be able to take on bigger stuff the next day and so on.

[Simon Wegerif]: Absolutely, or there might be some intervention which will help you a bit. So if I get an amber in the mornings, then I often, you know, I will change my training to an hour aerobic bike ride around a particular route in the local forest that I really enjoy, that, you know, is visually stimulating. And I know that will help me make the best of my current physiological state.

But back to the question you were asking about when would you not trust ithlete, or in fact any HRV product that compares to baseline, and that is if you get up significantly earlier or later than your normal time. So one of the things about the waking measurement is that you are taking it after you’ve had the cortisol awakening response, so basically when light starts to fall on the back of your eyes, even through your eyelids, it kicks off the cortisol awakening response, which basically gets your body ready to get up and start being active again. So it banishes the melatonin, and it starts the sympathetic nervous system to a certain extent, enough to get you out of bed and get moving in the morning.

Let’s say you normally do that at 7 a.m., and then one morning you have to get up at 4:30 in order to catch a plane or something like that. This is something that I noticed quite early on, that my HRV would, in that situation, be much higher than normal.

[Damien Blenkinsopp]: Ah, because parasympathetic is higher.

[Simon Wegerif]: Yeah, basically. Because my body was still in sleep mode, so the parasympathetic was dominant at that time.

[Damien Blenkinsopp]: So, basically, the circadian cycle is very important to control for.

[Simon Wegerif]: It is important to control for, and some people — I think everybody, once they realize that, that really your morning measurement should be +/- 45 minutes, something like that —

[Damien Blenkinsopp]: So I’m thinking jet lag is — because I just came from Europe to the U.S. a few weeks ago, and my HRV has been a little — I think I was surprised to see how high it was, given how tired I was feeling. So maybe that had some of the impact there.

[Simon Wegerif]: It could do. It could do.

[Damien Blenkinsopp]: Or do you think you adjust pretty quickly in terms of that cycle?

[Simon Wegerif]: I don’t think you do adjust that quickly. We’ve had so many stories reported back to us over the past few years. An Australian coach has said, ‘I never realized what an impact jet lag had on my body,’ and that was by doing HRV measurements, and he was flying backwards and forwards between Australia, Europe and America. And those are long haul flights. I think one rule of thumb is something like your body needs a day to adapt its circadian rhythm to each hour of time zone change. So if you’re doing all that trans-Atlantic or trans-Pacific travel, you’re going to have a really hard time getting adjusted, and your HRV is going to give you feedback on that.

[Damien Blenkinsopp]: Yeah. So the only other confounder is basically the issues is controlling for circadian rhythm and other things you’re introducing, like caffeine or those things. But in terms of actual scenarios, the only other one you’ve seen is where you continue to overtrain and eventually get to this adrenal fatigue situation, without introducing — and then the other scenarios are where you’ve introduced either a circadian or some other confounder in terms of stimulant or activity which is influencing your HRV?

[Simon Wegerif]: Yes, I would say so. Water has some interesting effects on HRV. Hydration level is something that — you know, some of the professional teams that are using ithlete, they want to control hydration level.

[Damien Blenkinsopp]: So are you saying dehydrated would lower your HRV, potentially?

[Simon Wegerif]: Yes, because it stresses the system, so, yes, that will tend to make you more sympathetic dominant. But, of course, that’s something that’s quickly fixable, right? You drink water, and within 15 minutes that HRV will have been restored, because your body absorbs water so quickly. So that will give you a false low.

[Damien Blenkinsopp]: Right.

[Simon Wegerif]: So if you woke up dehydrated and you were normally fully hydrated, you will get a falsely low — I mean, it is a low HRV at that point in time.

[Damien Blenkinsopp]: It’s relevant, yeah.

[Simon Wegerif]: But you have to take it — it’s relevant; it’s important, but you don’t have to take it easy the whole day —

[Damien Blenkinsopp]: Yes.

[Simon Wegerif]: — because recovery from that particular situation can be very rapid. You just drink large glasses of water and you’re right as rain.

[Damien Blenkinsopp]: That’s a good point. It’s a momentary HRV lapse, a decline. Are there any other scenarios where there are HRV’s you can quickly addressed? I’m thinking training scenarios. I mean, obviously, there’s, maybe a stress scenario, caffeine and things like that.

[Simon Wegerif]: Yeah, mental stress is important.

[Damien Blenkinsopp]: So people can account for those kind of things by — hopefully, if they’ve identified it, then they can retake their reading in an hour or so and see if it’s readapted to their usual baseline.

[Simon Wegerif]: Yes, they certainly could do that, yup.

[Damien Blenkinsopp]: Okay. Well, so you’ve talked about some of the things you’re going to be doing in the future with the algorithm and the correlation. Is there any other future developments and things that you — like, if you’re looking at the whole HRV app space, is there other things you’re looking forward to or that you see could be possible in the future, 5 or 10 years? Where do you see it all going?

[Simon Wegerif]: Well, what I personally hope for is that HRV, it is starting to get credibility now in sports training and sports performance. You know, it’s becoming, thanks to some of the really quality research that’s being done, it’s becoming more and more trusted. I’d like to see HRV trusted as a precursor to Western chronic disease, and in particular I mean conditions like high blood pressure. High blood pressure is an autonomic imbalance disease, and basically high blood pressure can certainly be caused by chronic stress over a period of time, and the blood pressure regulatory mechanism starts to go adrift. But you will see, in the case of not only high blood pressure, but type 2 diabetes as well, that HRV will go out of what ought to be considered acceptable normal ranges months or even years before those diseases take hold.

So what I’d like to see is HRV used as an ongoing wellness barometer, if you’d like. So I’d like to see normality of standards create for HRV measures, and for those actually to be something that people do, perhaps on their own initiative, but something that primary care physicians, general practitioners, etc., are happy to discuss.

[Damien Blenkinsopp]: Yeah, because — I mean, today we take our — if we go to the doctor for a standard checkup, we have our blood pressure and we have our heart rate, standard heart rate taken. What you’re suggesting is potentially HRV could be a better measure, and it should be included in those, if we could be more standardized and stuff, because you’d see it decline steadily over time if there were some chronic issues building.

[Simon Wegerif]: You would, and you would see it declining outside of a normal range. We exhibited — we launched the finger sensor in V3 of the Apple Consumer Electronics Show in Las Vegas in January. We probably did 200 demos during whatever it is, the three days that CES is on, and we had people who illustrated HRV values which, by looking at them, some of them were predictable, and in some cases, people really needed to pay attention. So we had a very large gentleman who came to see us, who said he got diabetes and he hadn’t been exercising recently, and he got 35 on the ithlete scale. And that shocked even him, because that is a very low number. I mean, that’s an extreme case, but —

[Damien Blenkinsopp]: Was that lying down or standing?

[Simon Wegerif]: No, that was sitting. So we did — all of these demos were done with people basically sitting at a table. But I would like to see some normative ranges exist for people. And also by tracking over weeks and months, that they’re able to do what I’ve seemed to been able to do, which is to basically find ways to keep my HRV increasing over the long term as opposed to declining with age. HRV is a very good forward looking indicator, and that’s why I sometimes call it a barometer. You know, it’s telling you about the weather to come, rather than the weather as it is right now. I would like to see it accepted and accredited.

And I think there’s been a useful start made in that area recently. There’s been this announcement about the Palo Alto prize, and that basically is, I think, either a half million or even $1 million award to researchers who can show initially in laboratory animals that they’ve developed techniques which would cause animals’ HRV not to decline over a period of time. The idea is that that will be applied to human studies later on, once the techniques are proven. So HRV is starting to become recognized now as a longevity indicator.

[Damien Blenkinsopp]: Right, right. You wouldn’t have seen it yet, but we also interviewed a guy named Todd Becker who’s very interested in hormesis and aging and longevity, and you might have read his stuff.

[Simon Wegerif]: Yup.

[Damien Blenkinsopp]: He plays around with that to increase HRV.

[Simon Wegerif]: I did read it. His article on HRV was excellent, really, really good.

[Damien Blenkinsopp]: Yeah, so he has some interesting points on that. Look out for the interview when it goes up, because it has some relation with this discussion.

So in terms of places where people could go to learn more about this, are there any people or particular journals where you think are good sources of information about HRV?

[Simon Wegerif]: One of my observations about HRV, there’s this massive body of research out there, but unfortunately it’s largely untapped, and I think that’s partly due to the impenetrable nature of medical research language. What we have tried to do is also to summarize a number of what we regard as some of the most important articles. So on the ithlete blog, we have done a number of research summaries where we’ve tried to take — captured the essence of what we regard to be some of the most important papers and put it up there for people to look at.

Also, we’re doing a new website where we’ll be putting more resources in there. I think Todd Becker’s article is an excellent introduction to HRV with a really good — a really good, if you like, approach to experimenting with different interventions on himself to see what made a difference. I think Andrew Flatt is doing some very good work at There are a few sites around. And even Men’s Health carried an article or two on HRV over the past year.

[Damien Blenkinsopp]: Was that a good quality article, or was it just good that it’s getting the word out there?

[Simon Wegerif]: It’s good that it’s getting the word out there. I think reasonably brief at the moment. But HRV is getting more mentions in the mainstream press, which I think is important.

[Damien Blenkinsopp]: Great. Okay, so I’d like to round off with a couple of personal questions. I always like to get some information about how people like you, who’ve obviously spent a lot of time thinking about data on biology and working with it, actually make use of it. So what kind of data metrics do you track for your own body on a routine basis? HRV, I guess, obviously. But beyond HRV, or in the specific context of HRV?

[Simon Wegerif]: I’m always wrestling with how to quantify my training. So training load is something that’s interesting to me. And I don’t think that any of the existing measures are really adequate.

[Damien Blenkinsopp]: So is that — are you talking about cycling or — you’re talking about volume?

[Simon Wegerif]: Yeah, that is the point. So training load metrics, there are many of them. So how do you quantify any kind of workout? If it’s cycling, is it miles? Is that a good — is that a good indicator? Is it average heart rate? Is it something about zones, the amount of weighted addition of all the zones you are doing? In team sports, they use RPE a lot, which is rating of perceived exertion. They also do translations from GPS data using group statistics for acceleration levels and running speeds and things like that.

But all of this training load stuff, what are we trying to achieve exactly with respect to — you know, training is all about stimulus and adaptation. From what I can see in endurance sports, there’s two completely different kinds of stimulus that we provide to the body, both of which seem to be necessary, and both of which are very helpful. One is this aerobic stimulus, which some people call the long, slow distance, and the other one appears to be the high intensity stuff. So how should we quantify each of those, other than by observing Kenyan runners who win all the long distances races and seeing what they do? I’m really interested in the science and the biology and the physiology behind that.

There’s all the stuff about calories. How do we measure calories? Why do we measure calories? What exactly are we going to do with that information? That stuff is of interest to me. Calories was of interest, before I did this trans-Alpine cycling, because I wanted to lose weight, but I wanted to do it in a controlled way, and in a safe way as well. So I didn’t actually damage either my health or my sports performance, but I wanted to lose 7 kg, just a stone, a reasonable amount of weight, and I wanted to do it very safely.

[Damien Blenkinsopp]: So you focused on calories to do that?

[Simon Wegerif]: I ended up actually focusing on food types. So what I actually did as advised by my good friend, Dr. Mike T. Nelson, was actually just to deliberately introduce a lot more protein into my diet, and basically diet — there’s an easy way and a hard way to diet, and I think the hard way is to think about all the things that you can’t do. And I think the easy way is to introduce good stuff, and that will necessarily push out some of the other things.

And what I mean by that is — Mike’s advice, specifically, was to increase my protein intake dramatically. And one of the ways I chose to do that was by having a big omelet after training in the mornings every day. And that actually makes you much less hungry during the day for snack foods, biscuits, carbohydrates, things like that. I also asked my wife not to buy biscuits and not to put biscuits in the — or cookies in the cookie jar, so that those were just sort of taken out. I was also — with chocolate, I just said I’m only going to have two squares of 70% chocolate a day, and that’s okay. Because 70% cocoa chocolate is so strong that you don’t want lots of it anyway, but it does sort of just satisfy that need.

So by deliberately eating lots of protein, I basically pushed out quite a bit of carbohydrate, and that combined with the volume of training actually tailed my weight down quite nicely.

[Damien Blenkinsopp]: Right. You make an interesting point in calories, because there’s a lot of devices coming out to measure calories. One of the areas of investment. And obviously that’s been a huge focus for the last 30, 40 years in diet books and so on. However, there’s a fair amount of research now to say that calories are not necessarily the whole thing, input and output, and that it’s a bit more complex than that.

In our discussion with Jimmy Moore a couple of weeks back about focusing on fat. You focused on protein. He focuses on fat intake, and it has the same impact. It satiates you and you tend to lose weight, and you’re not counting calories.

Yeah, so this is arguing whether it is useful to count calories, and these are the kinds of discussions I love to bring up, because especially when the marketing and everything that is out there is saying, ‘Let’s count calories; it’s going to change our behaviors; it’s going to have an impact on our lives.’ But is it really as beneficial as it’s portrayed to be, or are there better methods, like we’re doing — we looked at using the ketonics, which measures your state of ketosis, and as long as you’re staying in a state of ketosis, you’re going to be losing weight. So there’s other approaches to it that may be more useful, depending on what you’re doing.

And the training load thing, I think, is also interesting, and difficult, as you said. There’s not really any measures. We talked to Doug McGuff from Body By Science. He has a very specific protocol which kind of allows to do that, but you have to use that exact training protocol; whereas, I think what we kind of really need to get to is like you were talking about, is we have the metabolic and the strength, or as you call it, the aerobic and the —

[Simon Wegerif]: The high intensity HIT.

[Damien Blenkinsopp]: The high intensity stimulus, and how do we quantify those? Is there any way to quantify those so that we can see what stressor we’re getting, and then we can see, oh, we got a decline in our HRV because it was that stressor. Right? And currently you’re trying to do this with qualitative measures, which is pretty much the best I’ve seen that exist today as well. I don’t know — so you haven’t seen anything? It seems you haven’t — on your journey looking for that, you haven’t yet found anything that might be better than a qualitative measure?

[Simon Wegerif]: No. I’m always looking for things which are practical, which people will actually do every day. So anything which is too complex to calculate, people might do it a few times out of interest, but then it’s not going to imbed itself as a habit.

One thing I will say about calories, though. This whole motto of ‘What gets measured gets done.’ So giving people some kind of feedback that they can relate to which motivates them is always important, and whether that’s steps or whether that’s calories, I personally don’t mind, so long as it motivates them to imbed good habits and to reach for smart targets and goals.

What I think the particular problem I have with calories is that, yes, perhaps you can measure calories out, calories expended. Calories coming in is pretty difficult, though, unless you’re really going to spend a lot of time not only looking at the back of food packets and weighing things out exactly, which can be done, but at the end of the day, it doesn’t seem to work out that well, either. I mean —

[Damien Blenkinsopp]: It’s very impractical. It’s very time consuming.

[Simon Wegerif]: It’s very impractical, and it doesn’t actually work out that well. So people who’ve tried to do this very exactly, like Nigel Mitchell, who is the consultant nutritionist for Team Sky and is a very well recognized and respected nutritionist, says that if you do this exercise exactly — so on professional cyclists, they use power meters. You can measure the exact number of joules that they have expended. They can also measure the efficiency of the cyclist in terms of oxygen consumption, they can work out very accurately how many calories in those guys should need, and even if you do do all the food weighing stuff and measuring and everything else like that, the weight balance doesn’t seem to come out exactly as you would have hoped. There’s some quite large inaccuracies in there, one of which I believe is potentially the fact that the calorie numbers on the back of the food packets are achieved by burning the product in pure oxygen and seeing how much heat it gives off, but to what extent does that really represent the way our digestive systems work? And do they always do the same thing with two forkfuls of pasta? Does it matter, you know, what else you’ve got in your stomach at the same time?

[Damien Blenkinsopp]: And your microbiome, which is another interview with recently did. Like, your microbiome can impact how you metabolize the food. So I think it is more than calories, and it seems like the research is steadily going towards that, but it actually seems pretty complex. You know, microbiome, the types of macro and micro nutrients that you’re consuming. But, as you say, if you’re counting calories, you’re potentially looking at helping yourself to behave better, so it potentially could help.

Just, I think there is a device and a crowd sourcing project which is tracking calorie input, so in a more convenient method, I think it’s still in crowd sourcing. I’ll put the link in the show notes, because I can’t remember the name of it, but it would be interesting to see if that one works out. Because, yeah, like noting down everything you eat is not something that I can see people doing for a very long time.

What has been the biggest insight about your own biology that you have drawn to date from any data or anything you’ve tracked?

[Simon Wegerif]: I will tell you, I haven’t mentioned before in this discussion, but it is actually HRV — so HRV biofeedback, which is another — another topic in its own right and may be one that you will cover in a future podcast, but one of the things in my journey to steadily increase my HRV was — I do tend to be quite a driven person. I do tend to get moderately stressed, and my wife is much calmer. She’s been doing yoga for a number of years, and she’s always told me, ‘Simon, you should try yoga breathing.’ And I must admit, I did poo-poo it a bit, until I actually had a chance to meet up with an old friend who was a yoga instructor, and he told me about breathing. And I started to relate that to HRV, and I built myself a little biofeedback app prototype, and that, over a period of just a few days, made a big change upwards in my baseline for about 5 or 6 ithlete points.

And that was a really — that was a really big insight for me, that I could increase my HRV and feel much better quickly by using basically guided, deep diaphragmatic breathing. And there are good reasons as to why that should work.

[Damien Blenkinsopp]: You were tracking — you were doing this for, like, what 10 minutes a day or something like this? And you were using an HRV device to see if you were raising it? Or were you just using the HRV for training every day, and just watching it? So it was like an experiment?

[Simon Wegerif]: It was like an experiment. I did my ithlete reading every morning, and then, I mean, you couldn’t help but notice how much it had swung upwards when I started doing this breathing practice. And what I found even more surprising was that when I experimented again by not doing it for a few days, my HRV remained elevated. So it seems to have a chronic effect on upwards HRV. And I think this is a technique that’s got a lot of potential for the future as well.

[Damien Blenkinsopp]: Yeah, very interesting. Great, great point. Okay, last question. What would be your number one recommendation to someone trying to use some form of data to make better decisions about their body’s health or performance?

[Simon Wegerif]: I think it would be do it consistently. Do it consistently. Preferably, you know, every day or several times a week, and do it for a period of time. And when you’re trying to — if it’s a measure that you’re trying to improve, like HRV, try to change just one thing at a time to see if that thing does make a difference. So just be a little bit scientific in what you do and how you do it. Because otherwise, you know, there’s so much data around now that actually deriving information from that data is in some ways getting harder, because there’s more and more data, more and more variation in it.

[Damien Blenkinsopp]: Great, great point. And yeah, the information overload is going to get worse as time goes on, because there’s so many devices and things coming out. I know I already have too many devices, and I’m trying to decide which ones I focus on. And HRV happens to be one I very consistently do, because it is very rewarding, and I notice the changes.

So Simon, thank you very much for your time today. It’s been a great discussion, and I can’t wait to put this out on the podcast.

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