A question that occasionally comes up is whether you could use heart rate variability (HRV) continuously, during the day, to identify mental stress with e.g. a wearable
In my opinion, the short answer is no
Here, truly less is more
For the long answer, see below 🧵👇
Normally, when we talk about stress, we consider all sources (mental and physical), as physiologically, there is ~no difference (see slides 23-24 here: slideshare.net/marcoalt/heart…)
This means that you cannot separate mental stress from physical stress in HRV, in the "real world"
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This is also why HRV measurements should be taken in certain well-defined conditions, for example, first thing in the morning or during the night, so that baseline physiological stress can be captured in a repeatable context (more details here: medium.com/@altini_marco/…)
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I measure my resting physiology in two ways, which I consider equivalent (with some nuances):
• Morning measurement: 1 minute using the phone camera and HRV4Training
• Night data: average of the full night using the Oura ring (which I also pull in HRV4Training)
A 🧵👇
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I use both for obvious reasons (see bio), and have discussed previously in more detail night data: medium.com/@altini_marco/… - covering also the main differences with morning measurements
I always like to back up the theory with real-life data, so here are 6 months of data
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The data I am showing is the same I had shown a few days ago
I want to highlight how the data is extremely similar when there are no disruptions in heart rhythm, and how depending on your preference or constraints, you can pick whichever tool
Had mixed feelings at the beginning as we had an issue on iPhone 8, which was fixed for HRV4Training, but not for Camera HRV (showing poor results). This is most likely reflected in the reported quality though
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another important point is that at this point it should be clear that PPG vs ECG is not what the conversation should be about. PPG works great and can easily outperform ECG (see Firstbeat + chest strap ranking poorly)
Why? Because HRV is all about how you handle artifacts
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