Introduction to RPE/RIR
RPE/RIR is one of the most commonly used terms in today’s strength culture.
RPE stands for Rating of Perceived Exertion and is a measurement of how
hard training is. Mike Tuchscherer originally adapted RPE for strength
training to incorporate Repetitions In Reserve (RIR) (Table 1).
RPE
Description
10
Could not do any more repetitions
9.5
Could maybe do 1 more repetition
9
Could do 1 more repetition
8.5
Could do 1 more repetition, chance at 2
8
Could do 2 more repetitions
7.5
Could do 2 more repetitions, chance at 3
7
Could do 3 more repetitions
6.5
Could do 3 more repetitions, chance at 4
6
Could do 4 more repetitions
1-5.5
This scale continues
Table 1:​ The Rating of Perceived Exertion (RPE) scale based on Repetitions in Reserve (RIR)
In practice, RPE/RIR has served as a tool for lifters to adjust training based on
their daily readiness. Load can be adjusted by the lifter within the training
session to achieve the desired number of repetitions at the desired RPE/RIR.
This within-session adjustment is termed autoregulation.
In addition to being a practical tool for autoregulation, RPE/RIR provides a
quantification of how close to failure a set is terminated. In this guide, we will
use the RPE/RIR scale to frame the discussion of “how close to failure should
our training be for maximizing progress in muscle size and strength?”
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Commonly Proposed Model
To answer the question of how close to failure we should train, a few models
have been proposed. One such model that has gained traction is what we’ll
call the “threshold model” (Figure 1).
Figure 1:​ The “threshold model”
This model suggests that “effective” training occurs only in the range of 0-4
RIR or 6-10 RPE. While this may be a decent practical recommendation at
times, our interpretation of the research leads us to different conclusions. Our
interpretation of the research is discussed in detail ​here​. In short, there is a
significant amount of research indicating that lifters can train outside the 0-4
RIR range and still maximize gains in strength and size. This is especially the
case for strength.
Perhaps more importantly, the threshold model takes options off the table. In
our coaching experience, we often find some lifters cannot accumulate
sufficient training volume while only training in the RPE 6-10 range. We’ve
found that reducing average RPE can unlock progress for these individuals.
The mentioned factors have led us to create our own model (Figure 2).
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Figure 2: O
​ ur proposed RPE/RIR model
Our proposed model doesn’t differentiate effectiveness between RPE ranges.
This might seem unhelpful at first, but we’ll give more specific models for
each strength and hypertrophy in a bit.
At this point, things might seem a bit paradoxical. On one hand, we think
appropriate RPE/RIR is the most overlooked aspect to program design and
individualization - heck, we’re writing a guide on it. On the other hand, we
can’t offer an RPE/RIR range that’s “optimal.” That’s the point, though: a
​ wide
range of RPE/RIR can be effective​.
Our goal in the rest of this guide is to provide the conceptual framework so
you can decide for yourself what RPE range makes the most sense based on
the goal of the set (i.e. strength or hypertrophy) and your response to training.
Let’s start with strength.
RPE/RIR for Strength
For gains in maximal strength, our proposed model essentially flips the
threshold model on its head (Figure 3). Specifically, at a given load, the reps
early in the set provide a majority of the strength stimulus. In other words, it is
actually the f​ irst​ reps in the set that are the most effective for strength.
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Figure 3: ​Proposed RPE/RIR model for strength at a given load
This may seem counterintuitive at first. A 1 rep max (1RM) is slow and close to
failure (i.e. RPE 10). You may think that to abide by the principle of specificity,
it would make sense we try to mimic these traits in our training.
However, it’s important to keep in mind why a 1RM slow. A 1RM is slow
because it's really heavy. This is opposed to a repetition being slow because
you’re fatigued from the reps you’ve already performed in the set. The routes
at which a 1RM and the last reps in a set of 10 to failure become slow are
different.
It’s helpful to think through this in terms of force production. A 1RM is a test of
maximal force production. When you are performing a set of 10 to failure,
your ability to produce force ​decreases​ as you fatigue within the set. So,
through the lens of force production, the slow reps at the end of a set of 10 to
failure are actually less specific to a 1RM.
To conceptualize this further, revisit the basic physics equation:
force = mass x acceleration. ​As you proceed through a set of 10 to failure,
your ability to accelerate the given mass is reduced. Thus, as you get closer to
failure and the bar speed declines, the force production decreases. Since a
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1RM is a test of maximal force production, these reps become less and less
specific as they slow down with a given load.
To be clear, we’re not saying to avoid slow reps altogether. You absolutely
should practice some slow reps in your training. Having this skill is vital for
maximizing 1RM strength. However, if the goal is to practice slow reps, we
encourage you to design your training so that these reps are slow because
they are heavy, not because of the fatigue you’ve accumulated within the set
(e.g. a single at RPE 9 vs. the tenth rep of a set of 10 to failure).
RPE/RIR for Hypertrophy
For muscle growth, we simply want to put options back on the table. Based
on the current research, we’re not convinced sets need to be within 0-4 RIR
to maximize muscle growth. This is primarily in the context of heavy loads,
which we define as >75% of 1RM. If the load is >75% or above, we think the
primary advantage of training closer to failure is that more reps are being
completed per set and thus more volume is accumulated. If the total number
of reps at a given load are equated (as long as it’s >75% of 1RM), we think
hypertrophy outcomes will be similar (Figure 4).
Figure 4: ​Proposed RPE/RIR model for hypertrophy at a given load
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We’re still leaving the door open to the possibility that the reps closer to
failure (even with >75% of 1RM) are a bit more stimulative for hypertrophy, but
we’re fairly confident in saying this isn’t night and day. We’ll discuss how we
account for this uncertainty in the practical applications section.
As an example of our proposed model for hypertrophy, let's examine 24 total
reps being completed at 75% of 1RM via two different protocols:
1. 3 sets of 8 reps @ 2 RIR
2. 6 sets of 4 reps @ 6 RIR
Protocol #2 is an example of how you can set up training that violates the
threshold model but will almost certainly lead to the same muscle growth.
Since the load is sufficiently heavy, each rep completed is more or less the
same muscle growth stimulus no matter how close to failure that rep is.
Further, an advantage to protocol #2 is that many find this to be less
fatiguing than protocol #1, so more total reps may be able to be completed.
As a final point, training to or close to failure is probably necessary to
maximize muscle growth when using lighter loads.
Practical Applications
First and foremost, we hope you feel as if you now have more programming
options on the table than if you were to follow the threshold model. For
instance, if you find you experience disproportionate fatigue with sets to or
close to failure, you may want to explore lower RPE protocols. In our coaching
experience, we often find that this change can allow lifters like this to
accumulate the necessary volume to progress.
For strength athletes in general, we’d suggest reconsidering how volume
work is designed. As mentioned, practicing with heavy weights is going to be
part of any solid strength program, but the configuration of the volume work
is where things can get tricky. Instead of performing multiple sets very close
to failure, consider breaking up the same amount of total repetitions into
more sets. This will lead to less bar speed reduction, which means there will
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be more total force production, which will ultimately maximize the specificity
of this work.
For those with body composition related goals (physique athletes and
strength athletes far from competition), there are also more options on the
table. With sufficiently heavy loads (>75% of 1RM), training to or close to failure
does not seem to be required to maximize muscle growth. However, in
practice, we still bias higher RPEs when muscle growth is the primary goal. As
mentioned, we still have some uncertainty as to whether the reps closer to
failure are more stimulative for hypertrophy compared to the reps farther
from failure. Again, we’re fairly confident it’s not night and day, but we don’t
want to put all our eggs in one basket. We like to think about this as a
cost-benefit analysis. If there isn’t a massive fatigue cost to training close to
failure, it probably makes sense to accumulate your volume that way. Taking
your bicep curls to RPE 8-10 probably will not dramatically reduce the total
volume you can tolerate. If there is a disproportionate fatigue cost to training
close to failure for a certain exercise, then exploring lower RPE options may
be warranted. In our coaching experience, whether or not an exercise has a
disproportionate fatigue cost will vary from individual to individual, so some
tinkering may be required here.
We hope this guide stimulated some thought on how to best conceptualize
RPE/RIR, and most importantly, we hope you have some new tools in your
toolbelt!
- This RPE guide was created by Zac Robinson and Josh Pelland For further reading as well as the references that informed this guide, c
​ heck
out this article we wrote​.
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