What are training and HR zones?

Running stats — love them or hate them — as a runner, you will be constantly inundated. Finish a run, and you’ll get every data set imaginable, data that even ten years ago would have only been obtainable in a laboratory.

Amongst all that data are your heart rate (HR) zones and training zones. But what are they, and what do they really mean? Here, we unpack these zones, discuss their reliability, and explore how they are calculated.

Stats

My first GPS running watch told me on a digital screen how long I had been running and the time of day. Then, I progressed to a Garmin watch that took up half my forearm but also told me how far I had run and even my pace (ooh!).

I now run with a COROS Vertix 2S, which can navigate for me, take oximeter readings, electrocardiogram readings, let me know sunrise and sunset times, and almost tell me what to eat for dinner. One of the data fields that we runners vaguely keep an eye on—but few people know how to use properly—is heart rate information.

We’ve all heard of Zone 1 and Zone 2 running, but what do these zones mean, and should we be paying more attention to them?

Should I be bothered by HR zones?

In all honesty, the answer is yes and no. I’ll start with the reasons why you should.
Heart rate training has become far more accurate over the years, with the availability of chest and arm monitors improving the data, even compared to smartwatches.

Heart rate training is a progression from running by feel or running by pace, as both methods can be inherently inaccurate. Running by feel can vary substantially due to emotional factors, while running by pace doesn’t account for underfoot conditions, heat, altitude, humidity, or ascent.

HR training considers these factors, provided the data is relative to the individual (and this is where my ‘no’ reasons come in, but more on that later). HR data has numerous input factors, including sex, age, fitness, genetics, heat, dehydration, and even time of day—so it contains quite a few variables.

The zones

HR zones break down heart rate into bands, generally as a percentage of our maximum heart rate. A quick Google search for HR zone training will tell you that different watch brands and running apps have slightly varied parameters for these zones. E.g.

Strava:

Garmin:

To put this in perspective, Zone 1 would be a walking pace for most, or a slow jog, whereas Zone 5 would be an all-out sprint that could only be sustained for seconds.

You may have noticed a problem, though—not all zones are defined the same way. Now, add in the data suggesting HR zones are better represented by Training Zones. Training Zones are calculated differently, rather than being simple percentages of maximum heart rate. This is done using the Karvonen formula:

([Maximum heart rate – resting heart rate] x % intensity) + resting heart rate = Training Zone

Now we have HR zones and Training Zones, and both are dependent on at least one, if not two, key numbers: Maximum Heart Rate and Resting Heart Rate.

Maximum and resting heart rates

How can these be measured? A crude calculation is max HR = 220 minus your age. This is very rough, though, as it ignores all other factors except age.

An alternative method is to run a 5km time trial and, in the last 1-2 minutes, go flat out to absolute max effort. Then, before blurred vision and nausea take over, glance at your watch—the highest number you hit should be close to your max HR.

The most accurate way to calculate max HR is in a laboratory. For anyone serious about HR zone training, I highly recommend this—but make sure you complete the test properly and don’t stop early!

How to calculate your heart rate zones

To make use of HR zones in training, you first need to determine your own zones. The most common method is using the percentage system based on your max HR, but a more accurate approach factors in your resting heart rate. Here’s how:

For example, if your max HR is 180 and your resting HR is 60:

This method ensures that your zones are more personalised to your fitness level rather than a generic age-based formula.

Why train using HR Zones?

All the above aside, why would we even look at training in HR zones? You will almost certainly have heard of running your hard runs hard and your easy runs easy, and sticking to HR zone training is one way to encourage this.

By targeting specific zones, we can push our bodies to adapt physiologically in certain ways. This could include improving lactate processing, endurance, speed endurance, running efficiency, max power, and aerobic capacity. In this way, we quantitatively measure our training rather than relying purely on feel.

Whether you should focus specifically on HR zones in your training is up for debate. My personal take? They’re useful but should be used alongside other training parameters.

Check out our next set of articles, which address which key zones to target and how they help you become a better runner.

About the author

Simon James is a top contributor for expert running advice at LFTO. He's also the fearless founder of Run the Wild, a qualified mountain leader, and a monster at ultra marathons. James has completed several 100km+ races including the infamous UTMB, though his real passion is in helping newer runners develop their skills and unlock the joys of moving fast on the trail.