I think a key driver of HRV is the balance between sympathetic and parasympathetic in the ANS. Hence at a population level a low HRV will pick up stressed people.
Yes, definitely. For me, my HRV doesn’t seem to indicate very much. It’s pretty stable unless there’s something drastic like jet lag from changing time zone. However, my sleeping heart rate seems very sensitive. If it spikes anything more than 5bpm above normal, something is definitely (i.e. I’m going to realise I am sick 2 days later). It’s fascinating that such a simple metric can be so useful.
