[scheme271]

I'm not sure the body battery/stress measures are that great. Garmin is infamous for having an awful sleep algo and it still has a lot of trouble detecting naps. It doesn't bode well for being able to get stress data. I think it's good for generally determining high stress vs low stress and when you've overdone exercise recently but probably not much more.

[rolisz]

Body battery is amazing. I had long COVID/ME/CFS, and looking at the body battery when waking up was an outstanding predictor of how my day was going to be. When I hit 5% body battery, I was really feeling horrible.

[throwaway270925]

Interesting. What did you have to do to "charge" the body battery tough? And how does the garmin keep track of that?

[mikestew]

Naps and rest “charge”, and yes, Garmin keeps track of that.

Not that I put a whole lot of weight in those data personally.

[catigula]

It's just a collation of sleep-end RHR/HRV. It's completely trivial and many manufacturers do this correctly; both are extremely reliable predictors of recovery metrics.

Garmin has absolutely shitty sleep tracking but it doesn't matter; any wearable more or less nowadays can get static heart rate correct, leading to more or less accurate recovery metrics.

"Collect every paper you can find on RHR/HRV/etc. recovery metrics. Develop an algorithm for predicting recovery score per day based on the research" as a prompt to a Codex or Claude agent can probably get you 98-100% of the way there.

Edit: As a proof of concept, I had ChatGPT Pro 5.6 write the algorithm with my Fitbit data. Looks great.