HR zones debate and decisions

As I mentioned here and here, I started two weeks back a half marathon running plan with Polar, using the Vantage V2 and Stryd as main actors in the journey. In order to make sure that I use the full potential of the Vantage V2, I used the maximal running test to calibrate and define the heart rate zones. With a Max HR of 186 bpm, the Zone 1 and 2 were very low, forcing me to stay under 129 bpm for long sessions … which I found very challenging, forcing me to almost walk instead of run.

Based on various other posts available on Internet, I’m not the first one complaining that the Polar default zones are too low. Some say that is you who is not yet accustomed to use those zones and you should take the patience to accommodate over several weeks (more like 6-10 weeks at least, not 2-3 weeks). Maybe they are right, but when I looked at my Stryd power and power zones, staying the Zone 2 HR meant being at the bottom of my power zone 1, which was an indication for me that this is a bit too low.

Since Polar is using by default the max HR % to create the heart rate zones, I looked for alternatives, using the heart rate reserve which actually takes into account the resting heart rate in addition to max HR and using the Karvonen formula creates some zones that are higher that the default Polar and some say more accurate for training.

You can use this calculator and test various options.

For example, the Karvonen based zones are in my case (186 bpm Max – determined by Polar running test and 60 bpm resting heart rate – determined by observation – Polar has an article about that here):

For me the Karvonen based HR zones are more acceptable and in line with the power zones from Stryd. I adjusted the zones in Polar Flow and decided to continue the training plan. But something was bothering me … with every running test Polar will attempt to update the data (presuming that I’ll do the maximal running test) with the default %Max HR approach. I doubt that my Max HR would change too much, but still … I couldn’t feel the positive vibe of using the Polar approach but rather a tweaked version. The same I could have done with my Garmin, as it allows to set your HR zones based either on Max HR (like Polar), on heart rate reserve (Karvonen) or Lactate Threshold (Garmin’s recommendation) and I didn’t need to accept the compromises of the Stryd missing data [Polar only sends to Stryd Center the essential data, but not the optional Form Power, Vertical Oscillation, etc].

Early in the day today I decided to have a guided Lactate Threshold with my Fenix 6X – which I did to find out that my LT Heart Rate is 178 bpm. Based on that, the HR zones would be:

Since the Lactate Threshold with Garmin is still a taxing procedure, I can’t repeat that weekly … it’s close in intensity to the maximal running test from Polar (I reached 185 bpm during the LT test and 186 bpm during the Polar test … so, not that much of a difference). I count on the fact that Garmin will use some magic (FirstBeat algorithms) during my more intensive runs to detect the LTHR if that changes, without me doing another test explicitly (it happened in the past pretty regularly). That’s one of the advantages of having a smart device. Some purists would say that this is rubbish and that there are specific procedures to determined the LT (for example the one mentioned here and supported by Matt Fitzgerald) and the Garmin guided test is of no good. I suppose that, if Polar would have had a option to use the Karvonen formula and keep the data there with every running test, I would have not done the test with Garmin and stayed with Polar and their running plan.

I only know now that I closed a chapter with Polar Vantage V2, which is a very nice and capable device. I would still wear it because I like how it looks and its lightness, I appreciate the oHR to be better than Garmin’s. Polar Flow web platform is nice and intuitive but misses some elements that would make it even more attractive: power based structured workouts (you can still do something for your Vantage V2 on the mobile app), the integration with other platforms (Training Peaks, Final Surge or Stryd Power Center) would drive users (runners at least) to Polar I’d say and some other small (but important) bits like search enhancements for activities list, gear management, better Stryd integration, multiple alarms(?), support for Romanian character set. And it’s not that I miss them that much, I can live with small progress … but I fail to see Polar’s commitment to improve their platform, the recent changes were minimal … so if nothing happens in the next year, I’d say that they alone will only be attractive for people who really love their brand but they would be appealing users from other strong platforms.

Anyway, enough with ranting .. stay safe and enjoy your running!

LATER EDIT (May 2022): Most of my views didn’t change in the last year (February 2021), but I realised something that some people were mentioning in their posts on Reddit regarding Polar default HR zones – if you are persistent and you train using those zones, you can see the improvements and those don’t look so weird anymore.

I mean, even without following those Polar zones, but still with a significant portion of my running being slow running (low HR, low Power) I managed to be able to run decently with an average HR of 132bpm (6.9km with an average running power of 231W and a pace of 6:59min/km) or 134bpm (10km with an average running power of 238W and a pace of 6:48min/km). Looking back, in February 2021, I was just struggling to run with an average HR of 133bpm (8.44km with an average power of 203W and a pace of 7:41min/km).

All running power values come from my Stryd footpod [this is lower than the Polar running power values, in case you were curious].

No wonder that at that moment in 2021 I thrown the towel and said this slow running is not for me .. but even without forcing it too much, I ended up running a lot better (more efficient) after a while – almost a full minute per kilometer faster at the same HR.

So, in conclusion – I still think that Karvonen formula or LTHR based zones are better for me, but if I would start again with Polar training plans, I could live with the Polar HR zones. I have other areas to complain about Polar, but the HR zones (the default ones) are not that annoying anymore and if you are determined enough, you could get used to them and get better at running with low HR.