The 4th parameter – Rate of perceived exertion (RPE)

Written by Tihomir Stefanov, M.S.(C), PT

| Published on

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If you read our article on training parameters, you should know by now that we mainly measure our workouts on 3 parameters.

Those are the intensity, volume and density.

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To rehearse back briefly:

  • Intensity measures how close we get to our maximum strength capabilities (1 rep max on a given exercise is 100% intensity for that specific exercise)
  • Volume measures the total amount of weight lifted in a given set, exercise or a workout (Weight * sets * reps
  • Density measures the volume, referred to the time needed for its completion (Volume : Total completion time including rests between sets = Density)

Now, even though that will be enough for the most part, when it comes to creating a training plan, we can also use a 4th parameter – Rate of perceived exertion.

What is rate of perceived exertion?

This training metric is actually pretty old, as it first popped up in the early 1970s, in Gunnar Borg’s paper, called Perceived Exertion as an indicator of somatic stress.

RPE’s main function is essentially monitoring.

According to Borg, monitoring the individual perception of the stress can be used as means of fine-tuning the stress in a workout.

RPE Variations

borg scale

Just like any other concept, RPE went through a lot of transformations, since it was first introduced.

Let’s take a look at some of the most famous variations that have been proven to work times and again.

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Borg CS-15

The so-called Borg CS-15 was the initial scale of borg.

Even though sounds like the name of a Terminator, coming from the future, it’s simply a 15-step scale from 6 to 20.


  • 6 – No exertion
  • 7 – Extremely little exertion
  • 8 -=-
  • 9 – Very little exertion
  • 10 -=-
  • 11 – Little exertion
  • 12 -=-
  • 13 – Somewhat strong exertion
  • 14 -=-
  • 15 – Strong exertion
  • 16 -=-
  • 17 – Very strong exertion
  • 18 -=-
  • 19 – Extremely strong exertion
  • 20 -=- Maximum exertion

This scale is mainly used to monitor workouts that are done in aerobic conditions.

Note – Those are low-intensity, long in duration workouts, such as running, cycling and swimming

Borg CR-10

After having completed the initial scale, which was the CS-15, Borg decided to modify it, so that it is better suited for strength training.


  • 0 – Complete rest
  • 1 – Very light
  • 2 – Light
  • 3 – Moderate
  • 4 – Somewhat heavy
  • 5 – Heavy
  • 6 -=-
  • 7 – Very heavy
  • 8 -=-
  • 9 -=-
  • 10 – Extremely heavy
  • 100% intensity


reps in reserve chart

About a decade ago, the RPE/RIR scales were introduced to the fitness world.

RIR is an abbreviation for “Reps in reserve”.

The main contributor to the development of this scale is the famous powerlifter – Michael Tuchscherer.

Much like the CR-10, the RPE/RIR is a 10-step scale, but with slight differences.

First off, with RPE/RIR, the last step is number 10 and it represents the absolute maximum, which would otherwise be after 10 in the CR-10 scale.

The RPE/RIR scale is used to determine how many reps in reserve you have at the end of each set.

And so, for example a RPE-4 would mean that you have 6 repetitions in reserve.

Logically, RPE-9 would mean 1 rep in reserve and RPE-10 is an inability to do more repetitions.

Now, as this parameter takes into account the individual’s perception of the workload, the scale further breaks into half steps.

That is in case the individual is not sure if they can complete more repetitions.

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  • 10   – Maximum exertion
  • 9.5  – No reps in reserve but weight can be increased a bit
  • 9     – 1 rep in reserve
  • 8.5  – 1 or 2 reps in reserve
  • 8     – 2 reps in reserve
  • 7.5  – 2-3 reps in reserve
  • 7    – 3 reps in reserve
  • 5-6  – 4-6 reps in reserve
  • 3-4  – Weak exertion
  • 1-2  – Little to no exertion

Why is RPE important?

Well, RPE is simply a tool that further breaks the calculated workload through the individual’s perception.

This parameter is especially important for personal trainers, as they work up-close with clients.

That means they have to take every little thing into account – How heavy the client feels the weight, how they generally react to such stress, etc.

We also know that there are many factors that affect sports performance, which is exactly why we cannot always be at the peak of our capabilities.

This is where RPE comes in to help you calculate the exertion, according to how you feel CURRENTLY.

Pros & cons of RPE


As we mentioned above, the biggest advantage of the RPE is that you can calculate the proper workload for a certain workout, depending on the CURRENT state of the individual.

You cannot limit the approach to training on just the 3 main parameters.

You have to go outside of the box, as recovery is also subjective.

Odds are you felt this at one point of your training – Sometimes 80 kg on the bench press feel light and other times, 70 feel like 100.

That’s exactly why using the 1RM method we talked about here, is not the only thing you should use.

For example, 70% intensity is 70 kg on an exercise where your 1RM is 100 kg.

However, the RPE for that weight will fluctuate, as already mentioned.

So is RPE better than 1RM and the other 3 parameters?

Not really, it’s not about comparison here.

We can more so say that the RPE can simply be a supplement to the other 3 parameters and the 1RM.

It simply compensates for what the 1RM lacks.


The main disadvantage here is the subjective nature of perception.

In a 2012 research of Hackett, CR-10 was used on experienced bodybuilders.

Some of the individuals that were tested, announced a RPE of 6-7, which upon testing, turned out to be a RPE-10, because the trainee couldn’t complete more repetitions.

Furthermore, during that research, it was concluded that the closer we are to failure, the more accurate the perceived exertion is.

In other words, when it comes to measuring loads with 4-5 reps in reserve, the scale is not really reliable.

Furthermore, another subjective factor is training experience – More trained individuals can perceive the exertion more accurately.

Another disadvantage is that the RPE can fluctuate, depending on the individual’s stimulant intake and mental drive.

In other words, you can add a couple extra reps if you get a pre-workout in or turn up the volume on some heavy ass metal song.

Even though this is a relatively old training concept, there are still a lot of gaps to fill when it comes to making it optimally effective.

How can you use RPE?

If you’re a beginner or intermediate, we wouldn’t advise you to focus on RPE, but rather use it as an addition.

This is simply because, as mentioned, the less experience you have, the less accurate your estimation of the exertion is.

When you advance however, it would be good to start off with some tests.

  • Pick a compound movement, such as the bench, squat or deadlift
  • Pick a random weight which you’re not sure how many reps you can complete with. Go for a rather heavy weight, which is at or more than 80% of your 1RM (Remember that at lower intensity, estimation is less accurate)
  • If you pick a weight that you think would allow you to do 5 repetitions, do 3, then briefly estimate how many more you can do and proceed to finish the set to failure.

That will show you how accurate your estimation is.

Bottom line

RPE is an additional metric, which trainees and coaches can use to optimize one’s workout.

The main advantage is that this parameter allows us to tailor the exertion according to the individual’s current state of being.

That however is also a disadvantage, as there are a ton of factors that play role in the levels of sports performance of the individual.

Ultimately, we should aim to just supplement the rest of the training parameters with RPE, especially if we do not have a lot of experience in the gym.


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