HRV: early thoughts on ECG versus overnight optical

In the short time I've been running ECG versus optical for my HRV reading, I've noticed a trend I find interesting: the optical HRV seems to be a good indicator of how well I slept, and the ECG HRV seems to be a good indicator of the effect of that sleep, versus the trailing load.

Take this morning: yesterday, I had my first dose of a T-blocker, two hours of electrolysis, and a corresponding dose of cocodamol (babe, if you haven't tried it, don't knock it). Basically a stressful day for the body.

This morning, three points of optical HRV - Garmin, Ōura, and my own based on Whoop - all said YES! YOU ARE READY FOR THE DAY!

Looking at the green line on the graph, you can see my ECG HRV tells a different story. Considering where my point would be between the two on the graph, it was definitely closer to the ECG.

A correlation I'm looking on building is between Vigor Vitæ, and the discrepancy between the two. My operating theory is:

• multiple good nights of sleep, defined by good optical HRV = VV close to 100 ex C.
• heavy drain on a day - let's say 15 or below - will take multiple nights of good sleep, and it'll take those nights to 'charge' back to 100, and for the ECG versus optical to correlate.

I'm at about n=21, so far too soon to tell, but seeing the trends develop is interesting both for the understanding of my body, and the products that the big recovery companies sell us. I'm minded of the Golden Age of Technology Suunto Ambit series that offered two recovery test options: one where you wore the chest strap while you slept (I find this annoying) and a 3m session. It's been a long, long time since I've seen that, and it'd make an interesting firmware walk.