Delighted to stumble across this thread! Took up running during lockdown and I'm hooked. Out of interest, I'm wondering if some of you could help or give me advice. I'm 29, 5ft 2 and 128 pounds. Wear an Apple Watch and resting heart rate is around 64 bpm. Have been analysing my most recent runs and max HR hits 185+. I seem to be spending a lot of my runs in HR zones 4 and 5. Not sure if this is something to be concerned about? A friend told me that I shouldn't really be running in HR zones 4 and 5.
Just to add to the other posters’ comments, I have a running coach and he sets the majority of my sessions by HR. I always used to run by pace but whilst it’s quite good to do this sometimes (for races etc) I found that my HR changed too much depending on various factors plus I live in a really hilly area so training by HR some of the time makes more sense!
Max HR should be calculated by age (as another poster has said). I think the 220 by age is a bit misleading, I’m no expert but women’s HR goes higher than men’s naturally so I think a max HR for you sounds reasonable - depending on how old you are. I am 31 and my max is probably around 190-192 based on my Garmin which again may or may not be too accurate! I also don’t think (but may be wrong again

) that resting HR has any impact on max HR.
I have always been told that to get the best results from running and hit the sweet spot between training effectively and avoiding over training and injury you should try strike an 80:20 balance between ‘easy’ runs and hard runs. For example, I know that my ‘easy’ HR zone is anything under 150, so when I do a recovery run (I do 1-2 of these per week for 45 mins) I make sure my HR is around and about there. If this means that I take walking breaks during my run, so be it! Lots of elite marathon runners take walking breaks during runs - there is no shame in it
Running in zones 4-5 is great for improving speed and fitness quickly but I definitely wouldn’t spend all my runs in those zones and you’d probably see more improvement doing intervals or hill reps where you spend less time in high zones with a recovery break in between.