By Natalie Grant, PTA

In the first blog about RPE and RIR, we learned what these acronyms stand for, how these tools came to be, and their intended use in various forms of exercise. But how do you use them…? Furthermore, what if you’re not familiar with your physical capacities? How does chronic pain or healing from an injury muddle your ability to tune-in? 

Rate of Perceived Exertion and Repetitions in Reserve help us not just train better, but also train smarter. Though they have their limits. RPE and RIR are attempts (excellent, well researched ones at that) at putting an objective measure to something that is ultimately subjective. These concepts rely heavily on one's ability to self-assess intensity and exertion – in general, let alone with accuracy. So here is some guidance to set you up for success. 

RPE and RIR are practically interchangeable, like peanut butter and almond butter. The image above has a great representation of how prescribing RPE 8 with RIR 2 is almost redundant. Some may prefer one over the other, and similarly some exercises lend themselves more towards one or the other. 

RPE is most useful for exercises with a high number of repetitions. Accessory exercises, like rows or hamstring curls, are great to use with RPE. Other exercises that lend themselves well to RPE are time-based activities, rather than repetition-based. This could be anything from biking to planks to a carry. 

RIR on the other hand is most appropriate for the “primary lifts,” aka the compound exercises performed right after the warm-up when you still have high energy reserves. The squat, deadlift, and bench press are quintessential primary lifts. And research supports this use of RIR. The Journal of Sports Sciences in 2012 studied bodybuilders performing squats and bench presses when they discovered that: 

...not only did participants report RPE ratings that fell short of maximal (less than 10) even when sets were taken to volitional failure (no further repetitions could be performed), but that the participants had a high degree of accuracy in estimating their number of repetitions remaining on a set. In addition, with each subsequent set the participants were able to more accurately gauge the number of repetitions remaining. 

TLDR; the closer a set was taken to failure in conjunction with accumulating fatigue from prior sets, the more accurate participants were able to estimate their RIR. Wow!

What numbers on the RPE/RIR scales should I aim for?

Our favorite answer… it depends! If you’re a regular gym-goer without injury, aim for working in the RPE 7-8.5 range or RIR 1-3. This is a high enough intensity to *actually* result in results! Yet not so high that you increase your risk of injury. The National Academy of Sports Medicine (NASM) states that training at RPE 10 or RIR 0, aka “training to failure,” here and there has its benefits, but “strength may be compromised due to over training” if someone frequently trains to failure.   

In addition, there are benefits to leaving a few reps in the tank! The Journal of Strength and Conditioning Research studied bench press performance and recovery against two RIR protocols: 4 sets at a relative high load taken to RIR 3, followed by a 5th set taken to failure; or 5 sets taken to failure each set. The researchers found that the reps in reserve protocol improved recovery in the participants, as well as improved both performance and exertion in subsequent sessions.

What if I’m NEW? 

Folks new to exercise tend to overrate intensity. Just about everything feels difficult in the beginning understandably! And being less familiar with signs of fatigue or how your body responds to a certain exercise, even well after the fact, makes it challenging to know “just how hard is hard?” We suggest sticking to RPE 5-6/RIR 4-5 to still get a good workout in while also acclimating yourself to this new endeavor. It takes time, so take time!

What if I’m ADVANCED? 

Advanced or experienced fitness folk tend to, you guessed it, underrate intensity. The study mentioned earlier from the Journal of Sports Sciences asked its subjects of bodybuilders to estimate how many more bench press and squat repetitions they believed they had left before failure. The authors found that all participants tended to underrate, by a significant amount, their RIR especially on the 1st set. This is a good reminder to check yourself before you wreck yourself, even for the pros ;) 

What if I have PAIN?

We agree with Barbell Rehab’s philosophy here… Whether you are currently dealing with pain or you are re-integrating an exercise that was once painful, start out in the RPE 3-4/RIR 6+ range. Make way for “small wins” and help your brain and nervous system pair positive stimulus with movement and exercise again! 

A unique twist comes into play when pain joins the game… RPE and RIR are based on exertion, not tolerance. So while your muscles may be able to lift 50 lbs without breaking a sweat (exertion), perhaps your pain levels disagree (tolerance). Thus, Barbell Rehab has introduced a new scale called Rate of Perceived Tolerance (RPT). 

Under RPT, folks are encouraged to be guided by their pain thresholds, rather than their exertional thresholds. When appropriate (there are always exceptions to the rule!), we at Empower Physio often use the “stoplight analogy” to convey RPT to our patients. 

Green (0-3/10 pain) = keep going.

Yellow (4-6/10 pain) = slow*.

Red (7+/10 pain) = stop**. 

*slow as in modify (intensity, rest time, load, duration, volume, etc) 

**stop as in stop that particular exercise/movement, not necessarily all exercise/movement

How Physical Therapy Can Help

Whether you have pain, are new to exercise, or are a seasoned gym-goer, physical therapy can help educate you on concepts like RPE/RIR (and RPT!) to stay safe, move well, and build a resilient body. The stoplight analogy above is one of MANY examples of how the Empower Physio team distills evidence-based research into actionable tools for your toolbox. Train well and train smart, my friends :)

References

Hackett, Daniel A, et al. “A Novel Scale to Assess Resistance-Exercise Effort.” Journal of Sports Sciences, U.S. National Library of Medicine, 8 Aug. 2012, https://pubmed.ncbi.nlm.nih.gov/22873691/.

Hall, Brandon. “What Is an Accessory Exercise? Everything You Need to Know about These Training Staples.” Stack, 8 Feb. 2022, https://www.stack.com/a/what-is-an-accessory-exercise-everything-you-need-to-know-about-these-training-staples/.

Helms, Eric R., et al. “Application of the Repetitions in Reserve-Based Rating of Perceived Exertion Scale for Resistance Training.” Strength & Conditioning Journal, Aug. 2016, doi: 10.1519/SSC.0000000000000218. 

“How-to: Reps in Reserve Periodization.” Cutting Edge PC, 10 Dec. 2019, www.cuttingedgepc.com.au/reps-in-reserve/. 

Mahaffey, Kinsey. “Reps in Reserve (RIR): What You Need to Know.” NASM, 2 June 2022, blog.nasm.org/reps-in-reserve. 

Mahaffey, Kinsey. “The Rate of Perceived Exertion (RPE) Scale Explained.” NASM, 17 June 2022, blog.nasm.org/rate-of-perceived-exertion. 

Mangine, Gerald T, et al. “Effect of the Repetitions-in-Reserve Resistance Training Strategy on Bench Press Performance, Perceived Effort, and Recovery in Trained Men.” Journal of Strength and Conditioning Research, 1 Jan. 2022, https://journals.lww.com/nsca-jscr/Fulltext/2022/01000/Effect_of_the_Repetitions_In_Reserve_Resistance.1.aspx.

Mash, Dr. Michael. “Returning to the Gym after an Injury: 4 Common Programming Errors.” Barbell Rehab, 17 June 2020, https://barbellrehab.com/returning-to-gym-after-injury/.

Mash, Dr. Michael. “The Utilization of Rating of Perceived Tolerance (RPT) as a Guide for Training with Pain.” Barbell Rehab, 26 July 2021, barbellrehab.com/rating-of-perceived-tolerance/. 

“Perceived Exertion (Borg Rating of Perceived Exertion Scale).” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 3 June 2022, www.cdc.gov/physicalactivity/basics/measuring/exertion.htm. 

Popadic, Elena. “RPE vs RIR: What Are the Differences? How to Use Them?” PowerliftingTechnique.com, 12 May 2022, powerliftingtechnique.com/rpe-vs-rir/. 

Ryg, Jeff. “Using Repetitions in Reserve to Improve Your Strength Training Workouts.” Mend, 19 Jan. 2022, https://www.mendcolorado.com/physical-therapy-blog/2022/1/19/using-repetitions-in-reserve-to-improve-your-strength-training-workouts.