[rojeee]

I've been tracking HRV for about 8 years and can conclude that (for me) any HRV measurement overnight using a wearable or related wearable readiness metrics are largely useless. Now, what I do - as recommended by Marco Altini, an HRV researcher - is measure in the morning, steated with a chest strap. I use his app, HRV4Training which I would recommend [1]. It's the only way to get decent data in my experience. HRV is so senstive to various stimulii you need to measure it under exacting conditions, which you don't really get when you are sleeping. Sleep stages matter, how you are breathing, body temperature, etc.

I think my Oura ring is great but... it consistently records average nighttime HRV of around 15ms, which is implausable. However, when I wake up and measure with my Polar chest strap I'll get a more sensible reading. Fully recovered it will by about 150ms. Hurting after a hard workout it will be around 40ms. Some other interesting experiences with oura/garmin/apple are:

1. Higher nightime HRV after drinking alcohol than abstaining for weeks but then I measure with a strap and it will be low as expected

2. HRV spikes when I get out of bed in the middle to the night to do childcare related things, when it should be lower when walking around

Another thing to note is that I think I have parasympathetic saturation which means due to physiology and environmental factors you actually end up with a super low HRV when you are lying down/resting. Endurance athletes often get it - I run about 100km a week and my resting HR when fully recovered is about 40 bpm, so I guess that's the reason. When I de-train then nighttime HRV goes back to normal.

If anyone is interested in HRV I definitely recommend reading Marco's blog [1], you will learn alot.

[1] https://www.hrv4training.com

[2] https://substack.com/@marcoaltini