Have A Heart (Rate Zone)

Thought I would write up a quick post on a bit of research/self-education I did this past week. This is not anything new in the world of running and there are plenty of websites out there explaining all of this. But it was new to me and if it was new to me, maybe it will be new to someone else. The topic was all about learning how to determine and set a custom heart rate zone for my training runs.


Before getting into a couple methods on how to set the heart rate zones, let me share a little bit of why I wanted to look into it. While training for my most recent marathon, one of the things I noticed was that all of my runs seemed to end up in zone 4 as measured by my Garmin Forerunner. That sounds pretty good - zone 4 seems like it is a sign of a good solid workout. I was suspicious though since I was always in zone 4 no matter what kind of workout I was doing - speedwork, long runs, easy runs - always the same.

This carried over into the recovery and maintenance runs that I was doing after the marathon but before my 10K training plan started up. The decisive factor really came during the final weekend when I was doing my long run and because of the heat and no real need to push it, I decided I wanted to slow down my pace for the final couple miles and try to keep my heart rate in zone 3. I quickly ran into a problem though as I pretty much could not get my heart rate to drop into zone 3. This was despite slowing down to what felt like little more than a fast walk.

After that, I decided to do some research and found an alternative method of setting/determining heart rate zones. On my Garmin watch, whenever I would tinker with the device or user settings I would frequently get messages asking me whether I wanted to set customized heart rate zones. I always opted for "no" which results in the watch using a "Percent of Max" method. For me, my max heart rate is calculated as 169 using the old 220 minus age method. I suspect it might be higher after a couple years of running now, but that is a tweak for another day.

Using the percent of max method, I end up with the following heart rate zones:

After doing some research, I learned there is another common method (there are actually some more like "Percent of Lactate Threshold", but I am not going into those for this post) based on "heart rate reserve". The heart rate reserve is basically the difference between your resting heart rate (as measured when you first wake up in the morning) and your maximum heart rate. In my case, thanks to the heart rate monitor in my Garmin, I know my resting heart rate is 42 and combined with my max heart rate, I have a heart rate reserve of 127.

To calculate heart rate zones using the HRR, which is an option on the Garmin so you don't have to manually calculate it, you take the HRR, multiply by the percentage you want to establish, e.g. 70% of max, and then add the resting heart rate to that. For instance, in my case 50% of the HRR is 63.5 and when added to 42, that comes up to 105.5 (rounded up to 106). Choosing the HRR option in the settings for my Garmin yields the following heart rate zones:

As you may note, at the lower levels there is quite a bit of difference. For example, zone 1 does not even start using the HRR method until I hit 106 bpm whereas using the % of max method I have already passed through zone 1 and I am in zone 2 by that point.

Going back to the run that finally triggered me to start looking into this topic, once I had slowed down my pace, my heart rate was fluctuating around 140-141 bpm. That was keeping me in zone 4. Had I been using the HRR method, that would have dropped me into zone 3, which would match up much better with the level of exertion I felt like was putting forth.

In my runs this past week, which have been a combination of mostly speed work or recovery runs, I am finding that my heart rate zones are spread all over the spectrum now. For the harder workouts, I am spending most of my time in zone 4 with tiny little bits of zone 5. More importantly, though, I am seeing much more zone 3 time roughly corresponding to the warmup and cooldown miles. Meanwhile, during the recovery runs I am just seeing zone 2 and zone 3.

This one tweak seems to have made a nice difference in how the reported heart rate zones are matching up with what I feel is the actual experience. And I have not even gotten into things like tweaking the ranges instead of just using the default 50-60-70-80-90-100 percent breaks for each zone. That will be an adjustment for another day.

I'll keep monitoring the results over the next several weeks during this 10K training plan to see if my initial impressions hold up and to see if this proves to be a more useful guide for me in assessing my level of cardio fitness.