I'm confused about low heart rate training Zone and which zone is meant with it.
My 23 heart rate zone ends at 130bpm. When running in that zone it is very relaxed.
According to the MAF formula my low heart rate zone ends at 142bpm.
This is in the upper part of Z3 aerobic Zone.
That BPM is don't consider low heart rate when running.
Isn't "low heart rate zone training" done at Z2? Or am I missing something?
To make it even more confusing, my Garmin watch suggest to do base training with a 138bpm HR which is another value. Which zone makes most sense to use for my base runs and why?
There's a lot to unwrap here, and the short answer is to ignore the heart rate and estimate your base run pace by perceived effort (breathing, ability to hold a conversation during the run).
Much of the confusion comes from defining your heart rate zones. There are three common methods: one is based on your max HR, the second on your heart rate reserve (max HR minus resting HR), and the third one on your lactate threshold rate (at which HR you cross from aerobic to anaerobic pace). The first two methods have the obvious drawback that the max HR is often mis-estimated. For this reason I prefer the lactate threshold HR, which my Garmin estimated very accurately. To make matters even more confusing, various literature uses different percentage ranges for HR zones. But wait, that's not the end to confusion. Garmin seems to categorize your runs by your pace, and not by your HR zone. So, for example, when I run my recovery run at 5:50/km and fully in Z1, Garmin tells me I had a base run. But when I run it at 6:30/km in a 50-50 split between Z2 and Z3 due to hills, Garmin puts me into recovery.
So, I wouldn't put too much stock into your watch and instead just focus on how you feel. If you run with someone, talk to them. If you are alone, occasionally talk to yourself. If you are able to talk normally, you are running in your low HR zone.
you can manually edit garmin HR zones to whatever you want (correct or not)
According to the MAF formula my low heart rate zone ends at 142bpm
180 minus Your Age is 142. I find MAF heart rate very accurate (considering breath pattern, perceived effort, etc.). This "142" value is "the maximum HR you should run at", not "your average HR for the total run". You have to keep it below that number for the entire run.
Z2 is also a calculated value given your Máximum HR (ex. all in effort in the hills), age and fitness level. If garmin says a Base run at 138 then it's pretty similar to MAF, so just focus on run relaxed, easy nose breathing, and keep an eye to avoid being over 142 on the steeper zones.
Zone2 is where one should focus to increase areobic function and where you should spend most of your time (for endurance and general health targets). Eat clean. Try to balance exercise with the rest of your life. Go hard once every other week.