Perhaps you’ve overheard trainers in the gym ask their clients “how many more reps do you think you could’ve done?” after a set, or maybe your physical therapy team has asked you “how challenging was that for you to complete?” These questions are more intentional than they may seem and are highly effective for training progressive overload. They come from two concepts called Rate of Perceived Exertion (RPE) and Repetitions in Reserve (RIR), and are used to gauge how easy or difficult an exercise is for an individual.
Rate of Perceived Exertion
Swedish researcher Gunnar Borg developed the RPE scale, now known as the Borg RPE scale, in the 1960s to help a person quantify how intense a given exercise was for them, or in other words put a number to their “perceived exertion.” It ranges from RPE of 6 to 20… Strange numbers, no? That’s because the scale was mostly applied to aerobic exercise and thus is based on heart rate: 60 beats per minute (bpm), which is considered the lowest “normal” resting heart rate, all the way to 200 bpm, which represents a very high level of activity.
The Borg RPE scale has since evolved to be more applicable to any movement method, anaerobic or aerobic. This RPE scale ranges from 1 to 10; 1 being no effort (like what you experience lying on your couch watching TV), and 10 being all out maximum effort (like “being chased by a bear” or “lifting a car off the ground to save a child” are some fun examples I’ve heard). Though the Borg RPE scale is still used occasionally, the updated RPE scale is most common and considers not just heart rate, but also muscular fatigue, how hard a person is breathing, increases in perspiration, etc. For instance, RPE 7 can roughly be attributed to 70% of a person’s maximum heart rate and/or 70% of a person’s maximum effort or muscular abilities.
Repetitions in Reserve
Renowned coach and powerlifter Mike Tuchscherer modified the RPE scale in his first book The Reactive Training Manual to have more objective usefulness for lifting athletes. The method behind RIR is to estimate how many more repetitions of an exercise you could have done before technical failure, or “an inability to perform the lift with good form” according to the National Academy of Sports Medicine (NASM).
One meta-analysis published in the Strength and Conditioning Journal quoted a study performed in 2012 out of the University of Sydney with some incredible outcomes regarding RIR and RPE. This research found that “participants had a high degree of accuracy in estimating their number of repetitions remaining on a set,” especially when compared to RPE. Furthermore, “with each subsequent set, the participants were able to more accurately gauge the number of repetitions remaining,” aka more fatigue meant more accurate RIR estimations (Helms et al., 2016)! And the more accurately someone can gauge their repetitions “left in the tank” so to speak, the safer they can train.
Limitations & How Physical Therapy Can Help
A limitation shared by both RPE and RIR is the ability to self-assess intensity and exertion – in general, let alone with accuracy. These tools have attempted to put a number to something that is ultimately subjective, and what if you’re not familiar with your own physical capacities? How does chronic pain or healing from an injury muddle your ability to tune-in? Physical therapy can help educate you on tools like RPE/RIR to stay safe, move well, and build a resilient body! Next month, the writers at Empower Physiotherapy will share what implementing RPE/RIR into your activities can actually look like and when to use one versus the other!
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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.
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/.
Tikkanen, Jami. “Reps in Reserve (RIR).” The Training Plan Help Center, 2022, intercom.help/thetrainingplan/en/articles/2920138-reps-in-reserve-rir#:~:text=What%20does%20RIR%20(Reps%20In,in%20reference%20to%20technical%20failure.
RIR Image From Fit-Philosophy (https://www.fit-philosophy.com/)