I have a whoop and the recovery metric it tracks (which is a 0-100 number of what seems to be 5-6 parameters in the current version and 8-9 in the upcoming one)

I have a whoop and the recovery metric it tracks (which is a 0-100 number of what seems to be 5-6 parameters in the current version and 8-9 in the upcoming one) is surprisingly good. I too was very skeptical of a single-dimension value but even when I don't have a "reason" to get tired early in the day it's still a good indicator of how the day is going to go.