It is recommended to measure Heart Rate Variability (HRV) for at least one month before using the data to make changes.

“the best way to use something like HRV is to measure it under the exact same circumstances every day so whether you're going to use um just a device uh on your watch or your phone or your bed or anything else or you're going to buy a special HRV on it's fine just take that measure at the same time um mostly this means first thing in the morning so you wake up you go to the bathroom you come back down take your measure or something like that you don't uh wait sometimes you took it before food then after or look at your phone like all these other things that can influence stress”

“because what I want to know is last you know 24 hours you did something yesterday you did a lots of things I assume you ate food you maybe worked out you maybe alcohol or maybe you didn't you did mental stress or maybe didn't you put your body in a situation where it had to respond for for the majority of the day to do something and then you went to bed and we want to see the result of that we want to see this stress and Recovery cycle that you went through yesterday because that tells us where your body is at right now how is it responding”