Great, thanks. I also used the mentioned “Cardio Drift” app on my watch, it shows Pa:HR updated every minute while I run. I noticed that it was <5% but decided to keep below those 139 bpm mostly (which so far is the lower boundary of Z3 in my watch).
Should I adjust that zone boundary or threshold a bit higher?
I plan to do more of these mostly Z2 runs for the next weeks, with one or two more intense days per week.
Thanks for the help.