Heart Rate Zones, Pace Zones & RPE (When to Use What Metric in Your Running)

In todays article, I’m talking about Heart Rate Zones, Pace Zones, and RPE (rating of perceived exertion). How they correlate with each other and how they are prioritised with each other in an interchangeable way depending on variables and purpose of your run on any given day.

One of the great things about running today is the amount of post run data we have available to us. Conversely, one of the not so great things in about running is also the amount of post run data we have available to us! On both sides, this creates interpretation challenges, influencer click bait culture, and ultimately mis guided mis-information.

Pace, heart rate and RPE (rating of perceived exertion) are all great metrics to use in your training, but one of the important things to understand is that they don't work independently of each other, and there isn't one metric that should always take priority. The hierarchy changes depending on the type of session you're doing, the terrain you're running on, the conditions, and sometimes simply how your body is responding on that particular day.

The challenge is knowing what information matters in what setting.

If your training schedule says to run easy at 5:45/km, but you're running into a headwind and your heart rate is climbing above your aerobic zone, should you keep running 5:45s? What about when you're running uphill and your pace slows by two minutes per kilometre? Or you're doing 60-second hill reps where your heart rate hasn't even had time to respond before you've reached the top?

So lets talk about what I call Running DNA- That’s really what this article is about. Not choosing between pace, heart rate or RPE, but learning how to use all three to make better decisions in your training.

Prefer to Listen?

This article is based on an episode of the NZ Nomad Runner Podcast where Char and I dive deeper into pace, heart rate and RPE training zones, including how to establish your zones and how we use each metric when coaching runners.

First, What Are Pace, Heart Rate and RPE Actually Telling Us?

Before thinking about which metric to prioritise, it helps to understand that each one is telling us something slightly different about the same run.

Pace is essentially an external measure of your output. If you're running at 5:00/km, we know how quickly you're moving across the ground. This makes pace incredibly useful for training sessions where we're trying to achieve a particular output, especially on relatively flat and predictable terrain.

Heart rate gives us information about the internal physiological cost of producing that output. Two runners could both be running at 5:00/km, but one could be comfortably aerobic while the other is working close to threshold. Even within the same runner, 5:00/km could produce a very different physiological response depending on fatigue, temperature, hydration, terrain and a whole range of other variables.

Then we have RPE — Rating of Perceived Exertion. This is simply your own assessment of how hard you're working, generally rated on a scale of 1–10. An easy aerobic run might sit around 2–3/10, a steady run around 4/10, tempo and marathon-specific work might move through the middle of the scale, while harder threshold and shorter race-specific efforts start pushing towards the upper end.

I think RPE can sometimes get overlooked because we now have so much technology available to us, but developing a strong internal sense of effort is an incredibly valuable skill for a runner. Your watch might tell you what's happening externally and your heart-rate monitor gives you another physiological marker, but ultimately you still need to learn what different training intensities actually feel like.

The really useful information comes when we start putting all three together.

Your Easy Run Is a Good Place to Start

Let's use a fairly simple example: a 50-minute easy run on a flat path on a calm day.

If you know your training zones reasonably well, pace is a useful place to start. Let's say your easy pace generally sits somewhere around 5:30/km. You can head out around that pace rather than sprinting out the door and waiting for your heart rate to tell you you've gone too hard.

Heart rate isn't particularly useful in the opening few minutes anyway. It takes time to respond to the workload, so initially you might see your heart rate sitting quite low before it gradually climbs and settles into what I sometimes call your aerobic operating mode.

After 15–20 minutes, you might be running around 5:30/km, your heart rate has settled comfortably within Zone 1–2, and your RPE is sitting around 2–3/10.

That's a really nice correlation. Your pace says easy.

Your heart rate says aerobic. Your body says easy.

You've now got three pieces of information pointing towards the same thing: you're achieving the intended outcome of the session.

This is one of the reasons I like runners understanding all three metrics rather than becoming completely dependent on one of them. The numbers can essentially cross-check each other.

What Happens When the Metrics Don’t Align?

Let's take exactly the same runner with exactly the same prescribed 50-minute easy run. Their usual easy pace is around 5:30/km, so they head out and start running at that pace.

Except today they've had a stressful day at work. Their young child was sick last night and they didn't sleep well. It's warmer than usual and they're slightly dehydrated. Few variables going on there!

Twenty minutes into the run, 5:30/km doesn't feel easy. Their heart rate is sitting much higher than normal and perhaps starting to drift into Zone 3. Their RPE is closer to 4/10 than 2–3/10.

"But my easy pace is 5:30/km."

Your easy pace hasn't suddenly disappeared, your not losing fitness and your not a failure. The physiological cost of producing that pace is simply higher today due to the variables mentioned above. So perhaps today's easy run is 5:50/km or 6:00 pace.

The exact number doesn't really matter. What matters is achieving the intended training stimulus-the intended training stimulus of this example is aerobic adaptation from an easy/aerobic run.

There’s a school of readers reading this who will be thinking: ‘So what, ill just run my normal 5:30 easy pace anyway even though it feels harder today’… Sure, you can do that. But if your intended goal of the run is to get maximum aerobic adaptation from this easy run- you will not be achieving that. You’ll be instead doing whats popularly called ‘grey zoning:’ Too slow to be a useful tempo run, too fast to be a useful aerobic run.

This is where understanding heart rate and RPE alongside pace becomes incredibly useful

Training Zones Are Also a Tool for Managing Training Load

There's sometimes a perception that heart-rate training is all about becoming obsessed with running slowly or staying in Zone 2- that’s not how I look at it as a coach.

Training zones are simply one of the tools we use to control the amount and type of stress we're applying to an athlete.

If I prescribe an easy aerobic run, I want that run to be easy because there will generally be other sessions during the week where I want the athlete to work considerably harder. We might have a threshold session, hills, a tempo run or a marathon-specific workout coming up.

Getting the easy training right means we can often work the athlete harder when it's actually time to work hard.

The goal isn't to make all of your running easy. It's to put the appropriate intensity in the appropriate place so that you can absorb the overall training load, recover, and continue stacking consistent weeks of training.

Your aerobic running builds the foundation, while the harder training helps pull your threshold and top-end capabilities upwards. Over time, those two things start working together and that's when running can become pretty exciting.

Metric Hierarchy

When to prioritise one metric (HR/Pace/RPE) over the other depending on the setting and environment of the run

Hills Completely Change the Hierarchy

Now let's take our easy run away from the flat path and put it somewhere undulating. Suddenly pace becomes considerably less useful.

If you're running uphill, maintaining your normal flat easy pace could turn an aerobic run into a threshold effort pretty quickly. Going down the other side, you might comfortably run considerably faster than your usual easy pace without increasing your effort.

The undulating gradient has changed the relationship between pace and intensity. This is where heart rate and RPE become more prioritised up the hierarchy.

Heading uphill, you might notice your breathing increasing and your RPE moving towards 3–4/10. You look at your heart rate and you're approaching the top of your aerobic zone- this is useful information.

Instead of worrying about the pace disappearing from 5:30/km to 7:00/km, you reduce your work rate. Take shorter steps, slow the legs down, or depending on your running level and the steepness of the hill, perhaps walk for a section.

You've preserved the purpose of the run.

Once you crest the hill and start heading downhill, the hierarchy changes again. Heart rate will naturally begin falling and pace will be heavily influenced by the gradient, so RPE becomes particularly useful. You're simply asking yourself:

"Does this still feel like an easy run?"

This sounds like a lot of thinking when it's written down like this, but with experience it becomes automatic, and a part of you. It’s similar to anything new in life that your trying to learn and implement: Lots of bandwidth required initially as you learn and apply, but over time becomes automatic.

Short Hill Repetitions Are Different Again

Now imagine instead of an aerobic hilly run, you're doing 6 x 60-second hard hill repetitions.

Heart rate isn't particularly useful (while in session) as the primary metric here, because it takes time to respond to going hard up hill.

You will have fully completed your 60 second repetition before your heart rate has properly responded to the effort, and it might even continue climbing after you've stopped!

Pace isn't particularly helpful either. GPS can take time to settle during short efforts, and the actual pace you achieve depends heavily on the gradient.

So for a session like this, RPE becomes king.

If I've prescribed a hard 60-second hill effort, I'm interested in the athlete producing the appropriate effort for 60 seconds. Their pace is what it is and their heart rate will respond when it responds.

This is a good example of why saying something like "I train by heart rate" or "I only use pace" doesn't really make sense to me.

The metric needs to fit the session.

Long Trail Runs Require Another Shift

Let's say you're heading out for a four-hour aerobic trail run with a good amount of climbing. We can kick pace down the road entirely as an in session metric.

The pace on a steep climb might be 12:00/km. On a runnable downhill it could be 5:00/km. Neither number necessarily tells us whether you're executing the session well.

Heart rate and RPE become much more useful.

I had a good example of this myself recently. I was out for a two-hour run with around 600–700 metres of overall elevation, and I used heart rate within this run as a metric as a confirmation to see how I was tracking.

I'd spent the previous few months rebuilding, where I wasn't particularly worried about heart rate because I had been keeping things shorter and flatter for the most part. I had been working mostly off RPE- this resulted in my runs being nice and chill vibes, as my body needed the extra time to get used to running consistently again in order to build up safely. (Thanks to Coach Kirrilly for building me ups safely and strong!)

Hiking up the climb, I was working around 3/10 RPE and beginning to border on 4/10. My breathing was increasing and I could feel that I was starting to work. I looked down and my heart rate was around 158 bpm, which for me is getting towards the top of my aerobic zone. Everything correlated.

Then I could see a steeper section approaching. Rather than continuing at exactly the same hiking speed until my heart rate and effort climbed beyond where I wanted it, I simply slowed my legs down and shortened my steps.

On another section, I could see the top of the climb just ahead. My heart rate again was around 158bpm, the effort was controlled, and I knew I'd shortly be heading downhill. In that situation, I didn't need to change anything as the hill was about to level off and I was about to be headed downhill.

Same heart rate, different setting, different decision. That's the part a number on a watch can't do for you.

Heat and Wind Don't Care About Your Pace Zones

Another area where understanding the relationship between these metrics becomes important is environmental conditions.

Imagine you've spent winter running your easy sessions at 5:30/km. Your fitness has improved, everything feels great, and then suddenly summer arrives.

It's 25 degrees, and there’s more humidity.

You head out at your normal 5:30/km and wonder why your heart rate is significantly higher, and the perception of your run feels much harder too.

Again, nothing is wrong, the environment has simply changed the physiological cost of producing the same output.

Wind can do exactly the same thing. Running 5:30/km with a strong headwind requires more work than running 5:30/km on a calm day, yet your watch records exactly the same pace.

Training in all weather whether it be an easy run or any other type of session, along with learning how to utilise all 3 metrics in your running is ultimately going to set you up better for race day.

Especially if on race day you get some weather thrown at you, or perhaps your travelling to a place for your race that has a different climate.

Because you’ve taken the time to get to know yourself as an athlete, implement HR, Pace, and RPE zones in your running, you’re going to be in a much stronger position to adapt and thrive from whats thrown at you on race day.

Listen to your body, pay attention to your metrics, and don’t ignore the warning signals!

RPE Is a Skill Worth Developing

For all the technology available to runners, I think one of the most valuable skills you can develop over years of training is a strong sense of RPE.

You begin to recognise what different intensities like easy, tempo, threshold actually feel like in relation to the data that your seeing in real time.

You can feel when you're sitting near the top of your aerobic range because your breathing changes slightly, you know what a controlled tempo effort feels like.

You know the difference between discomfort that is appropriate for the session and the feeling that you're pushing beyond what you should be doing today.

This doesn't happen overnight. I sometimes think of the first couple of years of structured running as a bit of an apprenticeship. You're not only developing your aerobic system, strength and running economy; you're also learning about yourself as an athlete.

Someone who has played sport throughout their life may already have a reasonable understanding of what it feels like to push hard, recover and regulate effort. Someone who comes into running later in life without much sporting history may be learning all of this for the first time.

That's exciting. It also means you don't need to understand everything immediately. Over time, the numbers stop being abstract zones on a watch and start becoming something you genuinely understand within yourself.

Your Running DNA

This is where the idea of your running DNA comes back in.

Eventually, you know roughly what pace you should be running before looking at your watch. You know when your heart rate feels higher than it should.

You know what the top of your aerobic zone feels like. You know when the heat means you need to back off. You know that the pace going up a hill doesn't matter.

You know that today's easy run needs to be 20 seconds per kilometre slower because you've had a stressful week.

And sometimes you know that you feel bloody fantastic and everything is lining up perfectly, your easy pace might be 10-20 seconds per km faster, it works both ways!

Pace, heart rate and RPE stop being three separate things you're trying to monitor simultaneously, they become this set of interchangeable, woven and absorbed training principles that are part of you and your Running DNA.

So, Which Metric Should You Use? Key Takeaways

The answer is all three, But not necessarily all three equally, all of the time.

• On a flat aerobic run, pace will help establish your starting point before heart rate and RPE confirm you're operating at the appropriate intensity.
• On an undulating aerobic run, heart rate and RPE become more important while pace takes a back seat.
• During short hill repetitions, RPE is likely to be your primary metric because heart rate and GPS pace simply don't respond quickly enough.
• On a long trail run, pace may become almost irrelevant, while heart rate and RPE help you manage your effort across several hours.
• And when heat, wind, fatigue, poor sleep or life stress enters the equation, the hierarchy may change again.

That's why I don't think runners should become obsessed with any one metric. The goal isn't to become really good at following your watch, its to become in tune with yourself, your body and your running.

Learn your pace zones. Learn your heart-rate zones. Develop your RPE. Pay attention to how they interact and, over time, you'll build a much deeper understanding of your own running.

That's your running DNA.

And once you understand it, you're in a much better position to train with purpose, adapt when things don't go to plan, and ultimately level up your running.

Stay in the moment and have fun!

About the Author

Chris Lucas coaches runners and athletes who are serious about levelling up their running. He also develops and mentors the CMF Coaching team, helping shape the coaching philosophy behind CMF Running. He's the host of the NZ Nomad Runner Podcast and is passionate about helping runners better understand the why behind their training.

Keep Learning

If you enjoyed this article, here are a few more coaching resources to help you continue learning.

🎙️Podcast: Heart Rate Zones, Pace Zones & RPE (When to Use What METRIC in Your Running)

📖 Related Article: 3 Marathon Training Questions Every Runner Should Understand

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