Reps in reserve (RIR) and relative perceived effort (RPE) are both excellent tools to help gauge effort and progress in the gym.
Understanding how hard you’re training, in both individual sessions and across training cycles, is useful as it helps ensure you’re working hard enough to elicit a growth response but not so hard that you produce unnecessary fatigue.
But as with many aspects of effective weight training, such as your lifting technique, programme planning and nutrition, they are also skills that require learning and practice to utilise effectively.
Below we cover the basics of reps in reserve and why you may want to incorporate the measure into your training.
What is reps in reserve?
Reps in reserve (RIR) is a measure of how many more reps you could do after you’ve finished your prescribed number in any given working set.
If, for example, you were working to failure you’d have an RIR of 0. That is, you couldn’t do another rep with correct form if your life depended on it.
At the other end of the scale, if you push out 12 good reps and feel you had another 5 in the tank you’d have an RIR of 5.
Reps in reserve is an evolution of rating of perceived exertion (RPE).
RPE is the same concept but in reverse, you mark yourself out of 10 based on how hard you were working. 10 being technical failure and 8 indicating you had a couple of reps left in the tank.
RIR and RPE are both methods to gauge your effort.
This is useful as it helps ensure you are working hard enough to elicit a growth response but not so hard that you produce unnecessary fatigue.
This excess fatigue can hamper your ability to hit the training volume required for maximal muscle growth, across both individual sessions and longer term training cycles.
So RIR is a tool that can help you remain in the training sweet spot of 1-3 reps short of failure.
This helps maximise muscle growth while avoiding the excessive fatigue that can be caused by training to failure.
Reps in reserve (and RPE) research and history
Rating of perceived exertion (RPE), as a means of measuring effort, has been around for over 40 years with Gunnar Borg credited with devising the original scale and concept.
Originally used as a measure for aerobic activity efforts, RPE has since been refined over the years and widely adopted as a means of gauging efforts for resistance training too.
Despite being popular as a means of measuring both individual and total training session effort, it does have well-proven drawbacks.
Not least the fact that studies show that trainees tend to underestimate efforts when using the RPE scale.
That is, they report lower scores than their efforts actually merited. Meaning they were working harder than they thought they were.
This led researchers to look into better, or more accurate, rating systems better suited to resistance training.
Although a simple inversion, it seems that trainees are far more accurate at gauging how many reps they have left in the tank (RIR) than they are at scoring their efforts out of 10 (RPE).
This is despite the end result trying to report the same outcome, e.g. how close they are to technical failure in each working set.
For those interested in the full lowdown on the evolution of reps in reserve, take a look at this 2016 study by Dr Eric Helms et al – Application of the Repetitions in Reserve-Based Rating of Perceived Exertion Scale for Resistance Training.
The review provides far more detail than we can fit in here and explores the methods for incorporating RIR into your training, which we will also look at below.
Why would I want to use reps in reserve?
There are a few key reasons why you may want to incorporate reps in reserve into your training:
1. Reps in reserve helps you measure intensity and hit your volume targets
Sufficient training volume is key to stimulating muscle growth.
Numerous studies, such as this one, show that you should be aiming to complete anywhere from 12-24 working sets per muscle group per week to see maximal hypertrophic results.
(Beginners will see great results at the lower end of this scale, more experienced lifters will likely need to operate at the mid to higher-end to see continued gains).
Incorporating RIR into your programming allows you to monitor your intensity, ensuring you are working ‘hard enough’ to elicit growth, but not so hard that you impact your ability to complete the volume required.
For example, if your program prescribed 4 sets of 12 reps with a suggested RIR of 2-3 but you struggle to complete the first set, that is you couldn’t do another 1 rep let alone 2 or 3, this is a good indication that you need to reduce the weight or reps on subsequent sets to ensure you can complete all 4 sets and hit your volume target.
Conversely, if you are completing sets with more than 3 reps in reserve you may need to increase the weight or reps to ensure you are really working hard enough to stimulate growth.
2. Reps in reserve provide another benchmark measure of progressive overload
Once sufficiently experienced enough to accurately gauge your efforts, incorporating RIR into your programs provides another useful data point to measure progressive overload.
If you regularly exceed your RIR target, that is you finish working sets with more reps in the tank, then this is an indication you need to increase training intensity and up the weight, reps or sets.
If your RIR increases over several weeks for a given exercise then this is a good indication that you are indeed getting stronger.
3. Reps in reserve can be used to maintain intensity despite external factors impacting training
It’s a fact of life that external factors such as your sleep, nutrition and general life stresses can and will impact your training and energy levels.
Some days you will feel super strong and blast past your rep or weight targets and other days you will feel you can barely lift the barbell.
RIR can be used to ‘normalise’ your efforts across training with varying energy levels.
Again, given sufficient practice, you can use RIR as a measure of intensity despite the actual weight you lift and/or the reps/sets you complete.
For example, on Monday you may complete 4 sets of bench for 10 reps at 70kg and feel you had 2-3 reps in reserve, as per your intended target.
On Thursday, after a hectic 2 days with less than adequate sleep, you complete your first set of bench at 70kg and fail at 8 reps.
So you drop the weight to 60kg to complete the 10 reps for the remaining working sets and stick to your 2-3 RIR target.
Yes, you haven’t been able to shift as much weight but you have worked out at the same intensity, accepting your lower energy levels due to less than a perfect recovery.
Similarly, the use of RIR can help negate the inconsistencies that can arise from using your one rep maxes (1RM) as the basis for setting your weight, reps and volume targets.
Programming your training around your max lifts is beneficial. But you need to accept that a one off measure of performance, such as a one rep max, is susceptible to on the day influences. Such as your recovery, nutrition and energy levels.
Even if you set a true and accurate one rep max, your session to session lifting performance will vary.
This means that on some days working at 80% of your 1 rep max may be far too easy and on other days far too hard.
The use of RIR can help to smooth out these variances by helping you manage effort based on your day to day performance.
Criticism of using reps in reserve
The criticism often aimed at RIR/RPE is that most people underestimate their effort thus the measure isn’t an accurate indication of the effort they are deploying.
This is thought to be especially so in new lifters.
There is undoubtedly some truth to this as a new lifter has no way of knowing how hard they can really work.
And most of us do have an inbuilt tendency for self-preservation, which very often manifest itself as taking the path of least resistance.
For this reason RIR/RPE naysayers suggest the concept can confuse new lifters and that they are better just training ‘as hard as they can’ and/or ‘harder than last time’.
The problem with this sentiment is it doesn’t provide a measurable effort benchmark.
Telling a new trainee to train as hard as they can could be as equally meaningless as saying work to an RiR of 0.
They won’t know what technical failure feels like under either scenario.
But if they are scoring their efforts and recording changes over time they will at least have a yardstick to measure progress and increase intensity.
Why not just work to failure every set?
We cover whether training to failure is beneficial in our dedicated long read here.
But, in summary, the current research suggests that resistance training to muscular failure isn’t necessary to maximise increases in either muscle strength and/or hypertrophy.
And while training to technical failure may create a greater training stimulus, it will also create a disproportionate amount of fatigue.
This in turn can negatively affect recovery, subsequent workouts and thus your ability to consistently hit the sufficient volume and intensity levels required to maximise muscle growth.
In line with the current research our general view is that training to failure isn’t necessary or worth the injury risk.
This seems especially clear if your focus is on training for hypertrophy.
In this case, there seems to be a sweet spot, of working 1-3 reps from failure to maximise growth and balance fatigue.
That said, it may be worth incorporating training to failure in your routine every so often as both a means of benchmarking progress and keeping yourself honest regards your effort.
For example, working to failure on the last set of a specific exercise at the end of a training cycle wouldn’t be without merit, if done safely.
Also, as a general rule, working to failure is less of an issue for smaller muscles and isolation moves (e.g. bicep curls, calf raises, side delt raises) as you won’t cause too much fatigue.
You should avoid working to failure with the big compound moves (e.g. squats, deadlifts) too often, however, as the amount of fatigue created and the injury risk is not worth the limited benefits (1RM strength PB chasing notwithstanding).
If you are training to failure please only do so with a competent spotter and/or safety bars in place.
How to use reps in reserve in your training
Incorporating RIR into your workouts is simple and aims to achieve two main goals.
- To help manage training intensity and stick within your target zone; and/or
- Provide another data point to indicate when you are ready to increase intensity by, for example, increasing weight or reps
By using RIR to set your working weight you can keep your efforts in the hypertrophic sweet spot of working just short of failure.
Again, research has shown that this is the optimal place to work if hypertrophy is your primary focus.
Your aim is to work to an RIR of 1-3 for each of your working sets.
To stay in this range, simply record RIR for each set and adjust weight/reps either in session or week to week.
Once you are comfortable measuring and recording RIR you can also use it to provide an indication of when you are ready to progress in weight or reps for a given exercise.
For example, if you can finish your last set of a given exercise with an RIR above 3 it’s a good indication that you are ready to increase intensity.
Add 5% more weight or 1-2 reps until you are back working in the 1-3 range. Rinse and repeat.
RIR is also a useful tool to manage ‘peaking’ over a training cycle and to increase intensity over time.
For example, you have a 6 week programme and want to gradually build up the intensity over the weeks to prepare your body for a maximal effort in the final week.
Weeks 1-2 may see you squatting for 10 reps with an RIR of 4-5 and over the next few weeks you gradually increase the weight and reduce the RIR so that by week 6 you are working to failure (an RIR of 0).
You would then undertake a deload week and repeat the cycle, ideally with an increase in weight or volume.
Using RIR in this way allows you to manage your fatigue and more safely prep your body for gradual increases in workload.
Don't rely solely on reps in reserve to measure effort and progress
As stressed above, it takes time to learn how hard you can push your body and how many reps you may have left in the tank.
For this reason it isn’t recommended that newer lifters base their training progression solely on RIR.
It is more sensible to use it in conjunction with other typical lifting metrics, i.e. % of 1 rep max or a set number of reps/sets.
Studies have shown that more advanced lifters generally show very accurate RIR estimates so in theory could base their training and progression solely on an RIR or RPE method.
But it is still recommended that advanced lifters also make use of multiple data points.
Setting your reps in reserve benchmark
If you are confident in your 1 rep maxes for your lifts then you should use these figures to calculate your starting weights for individual exercises.
If your focus is muscle hypertrophy, a good guide is to complete your working sets at 60-80% of your 1RM and for around 8-12 reps.
So find a weight that checks these metrics and sees you working with an RIR of 1-3.
Alternatively you can test how accurate your RIR gauge is by completing a working set and then estimating how many reps from failure you were.
Take a 60 second rest and repeat the exercise but this time work to failure.
As stressed above, depending on your training experience you may have underestimated how many reps you could do and recorded a far lower RIR.
If so, adjust your weight/reps accordingly to get back to an RIR of 1-3. You now have your benchmark for future sessions.
Reps in reserve is most effective for moderate to higher rep sets
RIR is most effective at measuring effort at or very near to failure. E.g. 1-3 reps short.
It’s less useful for gauging moderate efforts, as it’s difficult to try and work to an RIR of 5 or 6, for example.
Similarly, if you are undertaking low rep sets for strength, e.g. 2-5 reps, then RPE and percent or your 1RM is probably a better way to go to regulate your effort.
Keep RIR for your hypertrophy training and for your moderate to higher reps sets.
Like many aspects of effective weight training, Reps in Reserve is a skill to learn and develop.
It will take time to learn to measure how hard you are working and how hard you can push yourself.
But once developed both RIR and RPE are useful tools to help gauge your efforts in the gym.
As a beginner you will underestimate yourself, and likely end sets with more reps in the tank than is optimal.
But using RIR as a benchmark to increase weight, sets and reps mitigates this somewhat, as you’ll be increasing your workload and intensity over time.
If you are finishing sets above your RIR target it’s a good indication that you are ready to increase the intensity by adding more weight, reps or both until you are back working at your target RIR.
Conversely, if you are seeing a drop in RIR it may mean you need to drop the intensity a touch to ensure you can still hit your overall volume requirement.
And if you are seeing RIR drop across multiple working sets and muscle groups over multiple sessions, it may be a sign that you need to ease off a little and add in another rest day or de-load week.
A good rule of thumb is to work to an RIR range of 1-3 for each set.
This way you are working hard enough to grow but not so hard you can’t complete all your sets or risk injury/exhaustion.
That said, provided you can do so safely, it is OK to work to failure occasionally (an RIR of 0) as both a means of benchmarking progress and keeping yourself honest with your effort.
Remember, intensity and hard work in the gym are paramount and you should never short change yourself, effort-wise.
But developing the skill of gauging your effort and using this to increase intensity over time can be another useful tool in your muscle building arsenal.
Try incorporating the measure into your next training cycle and see if it can help keep you honest regarding effort, and with managing your fatigue.