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Training Intensity: Understanding the RIR/RPE Scales

During class, you might hear (or read, for all you virtual folks) that you need to perform a movement at some percentage or number. And this can feel like a new language, especially if you are new to CrossFit.

So what exactly are RPE and RIR?

Great question. Both acronyms lead us to the same place: a rating for the difficulty of the exercise.

RPE “Rating of Perceived Exertion” – Useful for rating exertion across all exercise movements, not just powerlifting. The original scale was created by Dr. Gunnar Borg and ranged from 6 (no exertion at all) to 20 (maximal exertion) and has since been revised to go from 1-10.

As you can guess, the RPE scale can be unreliable because of the subjective descriptions: 2 people may perceive things differently, so they rate things differently. One way to correct this is to anchor the RPE scale to the RIR scale.

RIR “Repetitions In Reserve” – This scale took the RPE scale and made it accessible for powerlifters. This scale measures everything in terms of how many more reps you can do before muscle fatigue/failure.

As you can guess, the RIR scale isn’t useful for new athletes, or movements with either high reps or no reps at all (e.g., 5 min of monostructural activity).

The RPE/RIR scale
RPE/RIR Scales anchored to one another

The above table shows the RPE value (left column) anchored to the RIR value (right column) and the level of effort associated with them (center column). Most of your training will likely be in the dark blue to red range (RPE 7-10; RIR 0-3).

How do I know when I’m getting close to muscle failure?

The pace at which you perform a movement or lift will change throughout the set. For example, at the beginning of performing 10 repetitions of some lift, you feel fresh and not fatigued – these lifts are quicker (~1-2 seconds). As you approach 0-3 RIR, you might notice it takes 3-5 seconds for each lift. Towards muscle fatigue, you really need to push for that last rep. One recommendation is to video your workout and look at the timing of each lift.

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