Difficult for me to answer their exercise questions.
I exercise nearly every day (commuting), at low intensity, for not very long.
I also exercise a couple of times a week (training rides), at high intensity, for longer.
Significant meaningful difference to the results. I'm anywhere from 26 years fitness age to their generic "under 20" depending what exercise I leave in or out
I suspect my stupidly low RHR (low 40s, have measured it as low as 37 a couple of times) skews the calculation somewhat.
who is actually 38, FWIW