What's the Value of Heart Rate Variability in a Workout?

There's a lot of tools and devices now that have all sorts of diferent claims as to what they're going to do and tell you. Most of the stuff i've seen is on ora, which i'm one of the first 12 people to get one. If we look at the actual sleep metric itself, how i view those is that's just a response of the system. And prediction is very, very hard, right?If we go, ok, what is the biggest predictor of performance that's not performance itself,. boofh, i'd say all em kind of suck.