HR Zones displayed on the App

I find the HR zones that are displaying on the App to be a little odd from my perspective. The range, in terms of bpm, of the various zones appears to vary dramatically.

For example for me:
-Z2 is from 112-138 bpm (16 beats)
-Z3 is from 139-151 bpm (12 beats)
-Z4 is from 152-159 bpm (7 beats)
-Z5 is from 160-191 bpm (31 beats), the upper range of which is way above my actual max HR, and if we take my actual Max HR (174) the range is 16 bpm

Why does the app calculate the Z4 range to have such a narrow window compared with the other zones?

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Because based upon what it has calculated your LTHR to be and your max HR, based upon the data collected from lots of people that’s what they think your zones are. I wouldn’t worry about it too much. My Z3 has a range of 29bpm. We are all different, I wouldn’t worry about it too much.


Lots of HR info in this article if you’ve not seen in
Although there’s also a discrepancy there versus the zones that the app actually uses! - 4b in the article is start of 5 in the app. However once you’re above “threshold” HR is not so useful as a target (still really useful for analysis but that’s for elsewhere) so anything above zone 4 could just be called the suffer zone.

(I’ve changed the category to training as the SUF coaches may have some more informed info to add relating to HR and zones)