Stress… a high performer like you can’t do without it. So how should you manage it? ​This is the topic we explore in today’s podcast episode.

​Stress can manifest itself physiologically (intense training can lead to overtraining) and psychologically (when we’re under tight deadlines). Whichever form you’re grappling with, if you don’t manage stress you can quickly find yourself in an endless pit of feeling fatigued. We’ve all had those days, when it just feels like you’ve had enough but there’s no end in sight…​

What if there was an easy way to assess how stressed you are so that you can manage it before it becomes too much? What if there was a tool that would give you a red, yellow or green light before you’ve started your day and long before you hit burnout?​

​The good news is there is such a tool and in this episode I’m talking with its creator and data scientist Marco Altini. Marco developed the first mobile app that measures your heart rate variability (or HRV), the closest metric to represent how much stress you’re under, using just your phone’s camera. With the HRV4Training​ app, you can track your HRV fuss-free and instantly act on the feedback it gives you.
​But before we get into the how of tracking HRV, Marco and I discuss what HRV is and why tracking it can transform your performance and your daily life.

Tune into the podcast now to get the full de-brief or read the transcript notes below:

Download, stream, listen to the episode here:


Show notes

Find out more about Marco:

Twitter: @Marco_alt

Download HRV Tracking App: HRV4Training

Find out more about HRV tracking: HRV4Training blog



Today’s special guest is Marco Altini. He’s a high performer, a data scientist working on a variety of health tech innovations and an all-around interesting guy. He has brought the first of its kind mobile app for tracking heart rate variability that uses just your phone’s camera for recording.

We’ll cover:

  • what heart rate variability is,
  • how tracking it can help you reduce your daily mental AND physical stress,
  • how it can help you improve your health and longevity,
  • why daily data tracking is important.

V: Hey Marco, thank you for coming on the show. Let’s jump right into the nitty-gritty stuff. A couple of months ago I went to a biohacking summit here in London and HRV (heart rate variability) was the topic of every conversation. There’s just so much hype around it right now.

How did you get involved in it? How did you get hands-on with HRV and built an app out of it?

Marco: So I started tracking probably when I started developing the tools for tracking. I spent a few years during my PhD working with wearables sensors and physiological data. It was all in the context of monitoring physical activity. So a couple of years ago I was working at an R&D institute, where we had prototypes for ECG monitoring or EEG and such sensors before there were so many wearables on the market. And we did research and worked on developing technology to create these sensors but also on the data and algorithms.

The main point in my research there was that with wearables sensors and other products on the market you typically quantify what your activity level is – for example your energy expenditure in terms of calories or even just the steps you take – and I wanted to take these aspects one step further and work on more aspects that could provide more information on how this physical activity is changing your health status. In that case, cardiovascular fitness was my proxy to health as it is a very good marker of overall health.

So as I was working with all these data for quite some time during my PhD and more on the data analysis aspect and machine learning, and I did have a background in computer science engineering. Then I started working on apps as well so I could try to bring a part of what I was doing to anyone with an iPhone.

Before I was doing all this research and this monitoring using data coming from prototypes and it could only be limited to experiments you’re running in the lab with early iPhones. iPhone 4s was the first I think could actually connect to Bluetooth sensors and then you could start getting this physiological data on your phone and start pushing that into an app. That’s when I also started getting into HRV – one of the parameters that’s a very good marker of overall health and autonomous nervous system activity. That’s how I started to put together tools for HRV analysis.

V: With this extracted data, how do you apply it to your personal life? Surely you had some motivation to create a tool and collect this data. Why is it useful – why would anyone track their HRV?

Marco: Part of it was driven by training in the interest of trying to understand my physiology. Now, the tool is more refined and it’s all about training and performance, but when I started it was more about curiosity. Wanting to become more aware of how different stressors affect my body. It was also a lot about just making the tools – sometimes you’re driven to create things that other people can use rather than using it yourself. So as HRV measures physiological stress and it captures both physical stress (due to e.g. intense workouts) but also psychological stress (due to a stressful lifestyle, deadlines and work, travelling, poor sleep).

V: So let’s say I have those metrics on physical stress and emotional stress. How could I fix it? Is there a scale anyone could use to improve their lifestyles?

Marco: Unfortunately it’s not that easy. What you can do is… it’s important to always look at current data in light of your historical data. So looking at how your HRV trends change over time depending on stressors and that’s how you can begin to understand which stressors have the biggest impact on your HRV and you can make adjustments. Even if you don’t care about using HRV to improve your performance, if you’re not an athlete, you can use it improve your overall wellbeing.

V: For people who are new to this… here’s how I use it. I have maybe 10 workouts each week. I run and spend about 5 hours on running purely. There’s also strength training and then coaching people for obstacle races and endurance events. I get so knackered that I don’t know if I overtrained or it’s just mental fatigue. I use your app and what it does for me – it’s a red light. I measure it in the morning and t tells me if I overtrained and should take things easy that day. And if I were mentally stressed it would be affected as well?

Marco: Right, so the way we interpret the data for you, for example in HRV for training, which is the app where we provide more analysis and interpretation to make HRV tracking simpler to understand (some of the other apps we made are really research tools – you can do what you want with them but they don’t provide any interpretation of your data). We capture HRV (= physiological stress) and then we look at what’s your historical data, we look at your daily score – and your daily score might be lower on a given day because your body’s particularly stressed which is why we suggest to measure in the early morning when you’re not affected by many stressors. So the idea is that you’re in a condition similar to one we’d want in a clinical lab, in a study. In that condition still you’d be affected by psychological stress if there is some chronic stress that’s going on for days or weeks and that always has an impact on your physiology. That’s also why it’s a nice measure to track – because it gives you that score of your overall level of stress on the body.

So if your HRV is low, seeing how it changes over time you can try to make changes that would bring your HRV up.

V: Your app is the first on the market to track HRV using just your phone’s camera lens. How accurate is it?

Marco: The camera is as accurate as an ECG or a chest strap. You don’t have to take my word for this, we did many validations. We ran clinical studies, and recently in New Zealand with a group led by Paul Laursen, which is one of the main experts doing research on elite athletes and HRV. We started collaborating with Paul to run validation on the camera and algorithms where we had about 30 people doing different activities, like sitting and standing and post-exercise, with base breathing, without base breathing, using the camera and the chest strap ECG. We had pretty good results there. The method’s did well and we’re about to write a paper that will hopefully be published soon. This guy is really busy right now because of the Olympics – they coach some Olympic rowers.

We do have some data already published on the blog where we show comparisons with a Polar chest strap. Slowly it’s getting easier to show that the methods are actually so accurate that you don’t need to use a chest strap.

And we’re improving using the camera lens for measurement. We have an algorithm which can tell you if your measurement was accurate or not because we can check for outliers or noise in the data. Typically after 1 or 2 measurements, everyone gets used to doing this properly and then you can get data very accurately without having to use a chest strap in the morning.

V: That actually reminds me of my past because I started tracking my HRV a few months ago and I used the chest strap myself. It was so annoying – you can just imagine waking up early at 6am then having to reach for and put on the HR chest strap if you even have one.

Marco: You have to get it wet as well because normally these sensors can record well because you sweat while you’re exercising but in the morning – if your skin is dry, you need to get it wet and then it’s also cold and you need to go to the bathroom, come back then lay down. It’s just a pain. Especially when compliance is already a problem with data tracking regularly.

V: Can you tell us a bit about your work at Bloom Technologies? I know you’re tracking other metrics to improve lives. What is that about?

Marco: Bloom is a startup where we use wearable technology during pregnancy. We use sensors which measure biopotentials, let’s say similar to sensors that would be measured in EMG or muscle activity. During pregnancy we can also measure uterine activity so contractions and this thing called EHG which is electrohysterography. But yeah it’s basically EMG or muscular activity of the uterus.

And what we do is research on variation of physiological changes during pregnancy, so changes in uterine activity but also heart rate and heart rate variability – exploring some known and less known patterns rising over time. For example as the fetus grows you have to provide blood and then heart rate increases. So when we track these variables longitudinally, we do it with a goal to understand how it relates to pregnancy outcomes. For example to predict or detect labour, when it’s the right time to go to the hospital.

Then also we do some research related to complications – how these physiological signals change over time for regular pregnancies, for pregnancies where we have preterm birth or hypertension and so on. We look at these parameters from consumer perspective just because there are so many variables to consider. So we just released our sensors on the market, a beta version, and we hope to do more studies to collect data and understand more about this space that hasn’t seen much innovation in the last 50 years or more.

V: It’s fascinating. Digital health is evolving every day and the more quantified we get, the better our lifestyle get…

Marco: There’s some interesting opportunities when we have tools that are clinical grade or at least clinically validated. For example, HRV for training that is as matter-of-fact as laboratory protocols and tests. If you start collecting that data on hundreds or thousands of people, then you can understand much better how these variables relate to training as well as other physiological stressors.

We published a paper, our first paper for HRV for training, just a couple of months that I’ll be presenting in two weeks. There we had data from 700 users with up to 5 months of data per person. Typically in HRV studies you have 10-15 people measured once or twice in the lab so we got so much more data. We started analysing how much HRV changed daily, with respect to training. In the app, after measurement you’d enter tags which is just to provide context. So you say how you slept, if you trained yesterday, how intense your training was… So we could relate training intensity to HRV and we could show consistently that after intense training you have reduced HRV and a slightly increased heart rate. You show that even in unconstrained settings you can capture good data using just an app.

You can start stratifying by gender, age, and so on, to see how all these variables impact variations in HRV.

V: I know how overtrained people are these days. You usually don’t notice it until you’re just too fatigued. Do you have any ways to improve your HRV without resting? I heard of using meditation and progressive relaxation for this.

Marco: I don’t use any – I’m more curious about meditation effects. I’ve read of course much of the literature around this which is interesting. Let’s say we have positive acute effect when there are meditation and other practices aimed at increasing HRV. In the very short-term your HRV would increase, or maybe it would increase while you’re doing that activity. What’s interesting is how can you actually increase your HRV for the long-term, increasing your baseline. Because if it’s an acute effect that’s gone after half an hour, then I don’t think that’s actually making a difference to your baseline physiological stress.

But there are studies where you do these sustained practices like meditating 30minutes to an hour per day for months, and there they do see some more consistent changes. I think that’s a more interesting area of research. Can you actually change your baseline HRV to bring it up?

Since I made the app I see typical cycles that reflect periods of lower and higher stress for example training load. But overall even in my data I see changes of, even talking just about sports and fitness. SOme studies claim that HRV is related to your fitness level and it should increase over time as you get more fit. I don’t think that’s necessarily true, I think it’s a great tool in the short-term feedback loop. You train, you see an impact, you optimise your training. Then overall you will increase your fitness faster with less risk of overtraining.

But I think other metrics may be more representative of your fitness level, even just your heart rate at rest because that’s motivated simply by physiological changes e.g. the fact that your heart got stronger and your HR got slower. For long term changes in HRV, over months or years, we are still at the beginning of this kind of research. And now we have the tools to track this thing because before you had to go to the lab to do these measurements, once before the study and once during – I don’t think that was particularly meaningful to show what was changing as there are so many parameters.

Now that we can track daily and at home, I think we can do a better job of analysing how different parameters affect your baseline HRV and if you can actually somehow optimise it.

V: I recently saw a study from North Carolina University that single-player games like Bejewelled can not only improve HRV but also reduce measures of depression and other stress measures.

Marco: I think these are definitely having an impact on your physiology which can be positive especially deep breathing. The interesting question I think is does that impact your baseline or is it just short-term improvement that’s not sustained. I don’t know if there is an actual improvement at physiological level.

V: Do you have any habits which you attribute your success to?

Marco: Maybe consistency. Nothing special I would say.

V: What about your nutrition? What does it look like? Any dietary hacks – I find most people have some tweak that contributes to their high performance.

Marco: Yeah true, I would say nothing specific just trying to keep it balanced. I did my share of reading on performance nutrition and so I haven’t made drastic changes. I am intrigued by some of the things I’m reading these days on low-carb diets but mine is still mainly carb-based.

Sports-wise I run and cycle. I try to keep healthy but without any specific diet.

V: What other metrics do you track?

Marco: Workouts is probably the one I care about the most. I got a Garmin watch recently which has some interesting features. They partnered with FirstBeat, a company working on HRV but not only HRV so they did a lot of research on Vo2max estimation. Apart from fitness estimates, one of their features tells you how your workout is going to be once you’re 5-10 minutes in based on how your physiology is responding and based on your historical data. I find it works stunningly well in predicting how good my workout is going to be. BEcause if your heart rate is a bit higher at the same intensity then your body is tired.

Sleep is something I’ve been more interested in tracking recently. I’ve tried out different devices I wasn’t really happy with.

I need a clear goal if I’m tracking. The tracking itself also has to be easy, like measuring HRV with a camera, but still getting meaningful data.

V: Last question… what would you take to an uninhabited island.

Marco: So I’m definitely not a survival kind of guy so wouldn’t last long. I’ll go for running shoes and a book, for my mental health. And a knife just in case I really want to give this survival a shot. Otherwise that’s it.

V: Which book?

Marco: I was reading some books from Nassim Taleb – ‘Black Swan’ and ‘Fooled by Randomness’. They’re interesting books for people working with data, machine learning and predicting things. They show how biased we are, what we can predict and how truly random the world is.

V: Thanks so much Marco. This was a blast. For me tracking HRV is a daily habit – it tells me how intensely I should work out that day. I couldn’t do without that green or red light in the morning.

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