Recent articles and updates [November 2024]
Heart rate variability, wearables, entrepreneurship, training talk and some ramblings
hi there 👋
I hope all is well.
Here is my newsletter including articles and updates from November 2024. This month, I cover the Apple Watch’s failed validation, HRV normalization, sleep time detection issues, and more.
I hope you’ll find the articles useful and I would like to take the opportunity to thank you for your support.
Please feel free to comment below or in the articles should you have any questions, and I will follow up soon.
Take care!
Heart rate variability (HRV) 🫀
Should We Normalize HRV by Heart Rate? When it comes to heart rate variability (HRV), one common question is whether we should normalize HRV by heart rate. Heart rate and HRV are physiologically linked. A lower heart rate typically corresponds to a higher HRV (e.g. because of higher parasympathetic activity). However, the relationship is not only physiological but also mathematical, which might motivate the need for normalization. Learn more, here.
HRV Research. I discussed in my “morning protocol best practices” article how it is ideal to empty the bladder before taking your morning measurement, should you need to do so. This is important because just like in most other things we do, the nervous system is involved in emptying the bladder (e.g. in relaxing or contracting muscles, as well as sending signals to the brain that the bladder is full). A recent study by Faruk Dişli and Sedat Yıldız, titled “Effects of urination process on heart rate variability“ looks at this in more detail. Learn more, here.
Kyto 2935: a decent, cheap sensor for spot-check measurements. I collected some data using the Kyto 2935, which complies with standard protocols (i.e. it can be linked to any third-party app, like HRV4Training or HRV4Biofeedback) and provides two user-friendly options to measure, a finger sensor and an ear sensor. Check out the results in this blog.
Wearables ⌚️
Trusting the Right Tool for the Job. This blog was prompted by a recent paper showing issues in HRV measurements for the Apple Watch. As readers here will know already, HRV is one of the very few things that wearables can actually measure - even though this is the case only at rest (and we should call it PRV). Yet, not all HRV measurements are created equal, and recent research highlights the pitfalls of relying on hardware or algorithms not specifically optimized for the job. Learn more, here.
Wearables and Sleep Time, the latest research is out. In the past few years, I’ve worked quite a bit on sleep stage detection, first with Oura, to help develop their latest sleep staging algorithm, and then with a group of experts, to devise guidelines for using wearables in the context of sleep tracking. These efforts are documented in the papers below:
2023. M. de Zambotti; C. Goldstein; J. Cook; L. Menghini; M. Altini; P. Cheng; R. Robillard. “Practical Guidelines for Using Wearable Technology in Sleep and Circadian Research: A Position Statement from the Sleep Research Society”. See here.
2021. M. Altini, H. Kinnunen, "The Promise of Sleep: A Multi-Sensor Approach for Accurate Sleep Stage Detection Using the Oura Ring". Sensors. Open access here.
While I do think we made great progress in using movement and autonomic activity (e.g. pulse rate and pulse rate variability, temperature) to estimate wake and sleep time as well as to estimate sleep stages at the population level, it is quite clear to me that the data is not particularly accurate (or useful) at the individual level. But what does the research say? Learn more, here.
Podcasts and talks🎙️
Italian Olympic Committee: I spoke about HRV at the Italian Olympic Committee, covering among other things measurement timing and protocols, misinterpretations of the data, such as in case of abnormally high HRV, and the normal range.
HRV and Wearables. I was invited to discuss wearables by Henrik Børsting Jacobsen who is a professor in the Department of Psychology at the University of Oslo and who runs the Mind-Body Lab, together with Dan Quintana (associate professor in health psychology at the University of Oslo), and Fredrik Mentzoni (from Olympiatoppen where he integrates wearables into elite athletic training). We had a good chat, which you can find at this link. The discussion covers how wearables track metrics like HRV to assess stress, sleep, and recovery while also examining both the benefits and the challenges of interpreting this data accurately.
Other articles 📝
The Ultimate Guide to Heart Rate Variability (HRV): Part Two. You Measured, Now What? This is the second part of my series on heart rate variability (HRV), which I recently revised. You can find it here.
Escape Collective interview. Understanding heart rate variability (HRV) can improve your riding. What is Heart Rate Variability? How can you really measure HRV and what does the data tell you? How can HRV tracking make you a better cyclist? I answered these questions for Escape Collective (thank you Alex for the interview). You can find it here.
Building 🛠️
I’ve added normalized HRV to HRV4Training Pro, so that you can also verify by yourself if this is something that helps you using your data. Here is an example for my own data in the past two months. I am curious to pay more attention to this in the next weeks and see if I can spot any meaningful difference. Maybe a highly parasympathetic state (e.g. suppressed heart rate with increased HRV) looks different from just a ‘good HRV day’ (e.g. higher HRV with normal heart rate).
HRV:HR, or normalized HRV, as shown in HRV4Training Pro, which you can try here if you already use the HRV4Training app
Training talk 🏃🏻♂️🚴
An uneventful month, keeping volume high and intensity consistent. That’s how it should be, isn’t it?
Training log. As the name states, this is just my training diary for this year.
Ramblings 🤌
That’s a wrap for this month.
Thank you for reading, and see you next month!
Recent newsletters:
Marco holds a PhD cum laude in applied machine learning, a M.Sc. cum laude in computer science engineering, and a M.Sc. cum laude in human movement sciences and high-performance coaching.
He has published more than 50 papers and patents at the intersection between physiology, health, technology, and human performance.
He is co-founder of HRV4Training, advisor at Oura, guest lecturer at VU Amsterdam, and editor for IEEE Pervasive Computing Magazine. He loves running.
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