Last Updated on March 29, 2022 by Heather Hart, ACSM EP, CSCS
Scroll through any social media platform today and you’ll see running coaches making absolute statements about training methodology. “RPE is the ONLY way to go for ultramarathon” or “Zone 3 training equates to junk miles, you need to be in Z2 or Z4!” It’s easy to see why new – or even more experienced – runners get confused.
Hell, I am a running coach by profession, and sometimes all of the noise leaves me puzzled. So it’s no surprise that a question I often get from prospective clients is “do you train with heart rate, RPE, or pace?”
They might not be exactly sure what these methods entail, or why one might be superior to another. But they’ve heard these buzzwords floating around the internet and figure they must be important. So I’m sure I confuse these potential clients even more when I respond that we use ALL of these methods.
Running by RPE vs. Heart Rate vs. Pace: What’s the Difference?
My goal with this post is to explain exactly what each of these training methods mean, as well as highlight the pros and cons of each. I hope that by the end of the post you’ll be able to see why each method may be beneficial to runners, depending on their specific goals and circumstances. And further, why one method is not necessarily the “only” way to train.
What is RPE in Running?
“RPE” stands for rate of perceived exertion. Essentially, you as an individual are determining how hard you are working based on how you feel during that particular workout. The traditional Borg scale includes a rating from 6-20, with 6 being “no exertion at all” to 20 being a “maximal exertion” of effort.
This scale can get a little confusing though, so many coaches choose to use a 1-10 scale instead. Anyone who has ever worked with me, either as a running client or in person at the gym, knows I like to describe RPE as “1 – laying in bed” to “10 – being chased by a bear”. Hey, it helps to add real world scenarios.
(*edit to add, I’ve been informed by some of my clients that running from a Canadian Goose is more terrifying than running from a bear. So please edit this scenario as you see fit.)
Even further, sometimes we narrow it down to a scale of 1-5, as to not overwhelm newer runners who may overthink “is this a 4 or is this a 5?!”
How RPE works:
A workout is prescribed in a certain RPE range, based on the goals of that specific workout. The higher the number, the harder the effort. For example, if we’re using a 1-10 scale, a recovery run may be prescribed at a range of 3-4 out of 10. A base building workout, perhaps a 4 or 5. 800 meter intervals? Now we’re looking at closer to 8-9.
Benefits of RPE:
The RPE scale method of programming allows a client to truly become in tune with their body, and adjust their workouts based on how they are feeling on a given day.
Let’s say, for example, your normal “easy” recovery pace is around a 10:00/mile. But you slept poorly last night, perhaps your a bit dehydrated, and your body is still recovering from the previous day’s tempo run. Today, a 10 minute mile pace might feel too hard. So instead, you run at your current perceived “4 or 5”, without worrying about pace. This helps ensure that a workout designed to be easy truly is easy.
RPE is also useful on terrain that can cause sudden spikes in heart rate, such as hilly or technical trail. Trying to follow a prescribed heart rate or pace on a trail that is constantly presenting obstacles can be frustrating. Keeping an eye on overall RPE may be more beneficial than constantly tracking variables that may or may not be beneficial or even accurate on that sort of terrain.
Cons of Training by RPE:
On the opposite end of this spectrum, as a coach and athlete myself, I find that runners are not always honest with their RPE. And this could be for a number of reasons. Such as:
- You’re having a FANTASTIC run, and feeling really strong. You start running hard, and perhaps the rush of endorphins leaves this workout feeling mentally “easy”. In reality, you’re still pushing your lactate threshold, and not staying within the easy or aerobic pace you were prescribed, in order to achieve the desired physiological responses the original workout was designed for.
- On the other hand, sometimes we prescribe harder workouts, to help increase strength and speed. Some runners are intimidated by harder efforts. Maybe it’s the fear of failure. Or maybe the just don’t “like” that feeling that accompanies a hard effort (pounding heart, heavy breathing, perhaps a little nausea). So they convince themselves they are running at a 7 or 8 RPE, when in reality we as coaches KNOW they are capable of going much faster.
- You simply don’t understand RPE. Many runners – especially newer runners – think running always has to be hard. And as such, these athletes run all of their easy runs harder than they should, but still “perceive” that to be their “easy” pace, because that’s all they know.
- You’re a stubborn runner that assumes faster is always better, and fears “slower” numbers…maybe you fear that slower runs might make you “slower”, or simply fear seeing them on your Strava. I know your type, because a long time ago, I used to be one of these runners. I would have lied through my teeth and told you a run was “easy” when I knew it was hard.
Simply put: RPE is subjective. To be successful with training by RPE, an athlete has to not only be in tune with their body, but they also have to be able to separate emotion (both positive and negative), and be fully honest with the effort they are putting forth.
Running by Heart Rate:
Heart rate refers to how fast (or slow) your heart is beating at any given time. Measured in beats per minute (bpm), heart rate is a great indicator of how hard your body is working.
In the simplest terms, increased effort (like running) requires increased oxygen levels, and blood is the vehicle that carries oxygen to your cells. Not to mention, blood also carries fuel and nutrients to your cells, as well as carries away waste products.
In fact, blood does a lot of amazing things within our body, but for the sake of this post know this: increased effort (running) requires increased blood flow. Thus, the harder your effort, the faster your heart needs to beat to keep up with the body’s demand for oxygen.
How Heart Rate Training Works:
A workout is prescribed in specific heart rate training zone, based on the desired outcome of that specific workout. The most common “zones” used are numbered 1-5, and are based on a percentage of the athlete’s maximum heart rate, or a percentage of calculated lactate threshold heart rate. Here’s a brief explanation of each zone:
Z1: Light Zone – 50–60% of max HR or < 85% of LTHR:
Perfect for true recovery runs. Allows increased blood flow to muscles to aid in recovery, but does not put significant stress on the body.
Z2: Easy Zone – 60-70% of max HR or 85-89% of LTHR
Fat oxidization (using stored fat for fuel), capillary building, building a solid endurance base….this is essentially where you become better at running slow miles for a long time.
Z3: Moderate Zone – 70-80% of max HR or 90-94% of LTHR
Improve efficiency of blood circulation, begin training body to process lactic acid.
Z4: Hard Zone – 80-90% of max HR or 95-99% of LTHR
Carbohydrate utilization, teaching body to withstand higher levels of lactic acid build up. This is where you learn to push through the muscular fatigue that comes with running harder and faster.
Z5: Maximal Effort – 90-100% of max HR or 100+% of LTHR
Typically short bursts of high intensity exercises, useful for recruiting and training fast twitch muscle fibers (i.e. the opposite of the long, slow, running mentioned above). This zone should be used purposefully and sparingly, in order to avoid injury.
Now, for this method to truly work, we must have the most accurate picture possible of what is happening to an athlete’s body during each heart rate “zone”.
A simple calculation based on age predicted max HR (the classic “220-age” equation) is not going to be accurate. Ideally, a field test – or even better, a lab test – is done to predict lactate threshold and give a better estimate of max heart rate.
Benefits of Heart Rate Training:
I recently saw a quote regarding heart rate training that I loved. It said: “your heart keeps you honest.” I loved it, because it’s true, our hearts response to exercise is clear indicator of how hard our body is actually working. Now of course, there are a bunch of caveats, which I will address below.
But, for the sake of the “pros” section, let’s revisit the aforementioned athlete who is having a killer run, feeling amazing, and probably going much harder than they should, when in theory, they should be doing a recovery run. Even though emotionally and mentally they are feeling AMAZING, their heart rate will still demonstrate that the effort being put forth is harder than it needs to be. It is a measurement that is fully independent of how we PERCEIVE the effort to be, which can certainly be skewed.
For this reason, I choose to have athletes occasionally train by heart rate, so they can match up their RPE with heart rate zones, and ensure various paces are as easy – or as difficult – as they “think” they are.
Further, increased heart rate can be a great indicator of stress on the body. Perhaps you’re coming down with a cold, or maybe you’ve not recovered as well as you thought from your last hard race. This will typically show in your heart rate. And if the goal of a particular workout is to not put excessive stress on the body (such as a recovery run), then using heart rate as a method of understanding what the body is truly going through can be helpful.
Cons of Heart Rate Training:
As much as I am a fan of heart rate training, I’ll be the first to admit that this methodology does not come without it’s flaws. Let’s dive in:
Zone prediction calculations are not very accurate. I already mentioned that the classic “220 – age” prediction method is outdated, and simply doesn’t account for a persons current fitness level, genetics, gender, or a slew of other factors that may affect max heart rate.
Field and even lab tests have flaws. While I choose to use the Joel Friel method to predict lactate threshold heart rate, it’s still just that: a prediction. If an athlete fails to adhere to the protocol, is too nervous to truly push as hard as they can, or has faulty heart rate tracking equipment, these numbers are going to be flawed. Therefore, sticking strictly to the calculated zones may not yield the results we are looking for.
Speaking of heart rate tracking equipment:
Wrist based heart rate monitors are not very accurate. Though wrist heart rate monitors are now incredibly common in GPS watches, they are not very accurate. Researchers seem to agree that while optical wrist based heart rate monitors are “OK”, they are simply not as accurate as using a chest strap. (source, and another source, and some more sources)
Sometimes the athlete simply can’t run in a prescribed zone. If we are trying to help an athlete become a better runner, yet in order to stay in zone 2, they can only walk, we have a problem. A runner can’t become more proficient at running if they are NOT running. So in this case, heart rate training wouldn’t work.
Heart rate can be affected by SO MANY THINGS. It might be a shorter list if I simply told you what DIDN’T affect your heart rate! But let’s name just a few: hydration (or dehydration) status, caffeine, medications, weather (is it hot? cold?), cardiac drift, emotions, stress, thyroid issues, illness/infection…this is just a partial list.
Some of these are certainly warranted: stress on the body IS stress on the body, after all, and that’s what we are trying to measure by tracking heart rate. But a slightly increased heart rate because you just slammed a coffee doesn’t necessarily mean that a 30 minute run is putting “more” stress on your body than it would have if you DIDN’T drink that coffee.
Running By Pace:
Simply put, your “pace” is how fast you are running or walking at any given time. Typically, pace is measured in minutes per mile or minutes per kilometer, depending on where in the world you live.
How Pace Training Works:
A workout will be prescribed by pace. It could be an average for the entire workout, such as “maintain a 10:30/mile average for a 30 minute recovery run”. Or, it could be prescribed in intervals, such as “6 x 0.5 mile repeats at 6:15-6:30/mile”. With this method of training, the prescription is cut and dry: you run x:xx pace.
Benefits of Running by Pace
If you have a specific time goal for a race, you need to occasionally (if not frequently, depending on the race and athlete in question) train by pace. Your body needs to know what that goal pace feels like, and practicing that pace (or faster) allows your body to become proficient at that pace.
Cons of Training by Pace
Pace is independent of effort, as the effort it takes to run a specific pace is based on the fitness level of each individual athlete. An runner may choose a goal time for a race that they currently do not have the fitness level for. As such, predicted “easy run” paces may still be too difficult, resulting in that athlete training too hard, all of the time. This is a common cause of athletes burning themselves out, or worse, getting injured.
And even if an athlete IS capable of those paces, some days they may be capable of more, or alternatively, may not be feeling 100%, and need to run slower in order to achieve desired goals.
And as mentioned multiple times already, pace and terrain sometimes simply don’t mesh well. Tell an average runner to nail a 30 degree incline up a mountain at their flat road “tempo” pace, and frankly, it’s not going to happen, at least not for a sustained effort.
Which Method is Best for Me?
The million dollar question – which training method should you use, running by heart rate, RPE, or pace? And the answer, of course, is: it depends.
I know, I know, not what you wanted to hear. But let me give a few examples:
If you are an athlete running almost exclusively gnarly, technical trail with big elevation changes: RPE might be a better choice than heart rate or pace.
If you are a newer runner who doesn’t quite understand what “easy” or “hard” runs should feel like, heart rate training might be a great option for you.
If you are a runner who has pre-existing cardiac issues (cleared by a doctor to run, of course!) and you are on medications that affect heart rate: RPE and pace might be a better choice than heart rate training.
If you’re gunning for a Boston Marathon qualifying race, then pace specific work might be a better option for you.
Ultimately, it boils down to which option will allow you to a) stay honest with your efforts, and b) best help you achieve your unique running goal. And sometimes, that means incorporating all three training methods into your personal running methodology.
Heather Hart is an ACSM certified Exercise Physiologist, NSCA Certified Strength and Conditioning Specialist (CSCS), UESCA certified Ultrarunning Coach, RRCA certified Running Coach, co-founder of Hart Strength and Endurance Coaching, and creator of this site, Relentless Forward Commotion. She is a mom of two teen boys, and has been running and racing distances of 5K to 100+ miles for over a decade. Heather has been writing and encouraging others to find a love for fitness and movement since 2009.