What is RIR in training and how to use it

RIR stands for reps in reserve, and it is the number of reps you still have left in the tank when you finish a set. If you stop at RIR 2, you could have done two more reps with good technique. It is a simple way to measure how close you get to muscular failure without having to reach it, and it makes each set count without leaving you wiped out.

How the scale works

The idea was popularized by strength training researchers, such as Helms and colleagues in 2016, building on the rating of perceived exertion scale. Instead of saying "that was really hard," you pick a specific number based on the reps that were left over. The usual values are these:

1. RIR 0: you reached failure. You could not do another rep with good technique.
2. RIR 1: you could have done one more rep, but only just.
3. RIR 2: you had two reps left. It is a hard but controlled set.
4. RIR 3 or more: you had plenty of margin. Good for warmups or light sets.

What matters is that the rep you count is one you could do with correct technique, not one you would grind out with your body moving any way it likes. If the bar slows down a lot and your form starts to break down, you are close to your limit even if you could still finish a half rep.

RIR is similar to RPE, the 1 to 10 effort scale, but it is easier to explain. An RPE of 8 is roughly an RIR of 2, and an RPE of 9 is an RIR of 1. Zourdos and his team published a scale in 2016 that links the two measures for strength training.

Why it helps you progress

According to a good part of the hypertrophy studies, sets taken close to failure seem to give a muscle building stimulus similar to sets taken all the way to failure, with less accumulated fatigue, although the evidence is not definitive. That is why many programs recommend working at an RIR of 1 to 3 on most sets, and saving failure for the last exercise or for safe isolation movements.

This solves three common problems. The first is training too easy: if you always finish at RIR 5, you are probably not giving enough stimulus. The second is always training at the limit: reaching failure on every set piles up a lot of fatigue and makes it hard to recover for your next session. The third is not being able to compare weeks: without an effort criterion, you do not know whether you went from 8 to 9 reps because you improved or because you took it easier that day.

For progressive overload, RIR is your compass. If you do more reps with the same weight at the same RIR, you have progressed. You can see the full method in the guide to progressive overload, where RIR shows up as a criterion for deciding when to add load.

How to estimate it honestly

Estimating how much you have left is not easy, and the 2017 studies by Steele and colleagues confirm it: most people underestimate their remaining reps, especially when they are far from failure, and accuracy improves with experience. So if you are a beginner, your RIR will be an approximation, and that is fine. These tips help:

1. Start with simple, stable exercises, such as machines, the leg press or cables, where it is easier to feel the limit. Heavy, technical lifts like the squat or the deadlift are harder to judge.
2. Watch the speed. When the bar clearly moves slower than on your first reps, you are near the end.
3. If you doubt yourself, choose the lower number as a prudence measure. People already tend to underestimate the reps they have left, so this is not a rule for being more accurate: it simply keeps you on the safe side. It is better to think you have RIR 1 and actually have RIR 2 than the other way around.
4. Once in a while, practice going to failure on a safe exercise to calibrate your perception. Choose movements where failing is not dangerous.
5. Do not change it every set. Pick a target, for example RIR 2, and watch whether you hit it over time.

And a sensible warning: getting close to failure on risky exercises, such as a squat or a bench press, only makes sense with solid technique and, when appropriate, proper safety. If you have an injury, aches or a medical condition, talk to a health professional before you raise the intensity.

A concrete example helps. Imagine a bench press with 60 kilograms and a target of RIR 2. You do 8 reps and feel you could have done about 2 more: the set is right. The next week you do the same 60 kilograms for 9 reps with the same feeling: you have progressed, even though the weight has not changed. If instead the last rep came out in slow motion with no margin, log RIR 0 or 1, and next time keep the weight instead of raising it.

Which RIR to choose for each exercise

Not every set needs the same effort. Here is a practical guide you can adapt to your level:

1. Heavy compound exercises: RIR 2 or 3 on working sets, because reaching failure demands more recovery.
2. Machine or cable exercises: RIR 1 or 2, with an occasional failure on the last set.
3. Isolation (curls, raises, extensions): RIR 0 to 1 on the last sets, because the risk and the overall fatigue are lower.
4. Warmup: RIR 3 or more. It does not count as a working set.

A beginner can start with RIR 3 on almost everything and drop to 2 as technique gets more controlled. Someone with more experience can combine RIR 2 on most sets with a final set closer to the limit.

How this works in Elvyfit

In the Elvyfit workout log, RIR is an optional field on each set, with four values: 0, 1, 2 or 3 or more. If you do not want to log it, that is fine, but if you do you will have more context when you compare sessions. Next to weight and reps, the app colors each set against your previous session: more weight or reps, less, or the same. Warmups do not count toward progression.

The progression suggestion from the code is based on your last top set: with 9 or more reps it raises the weight (2.5 kilograms for upper body and barbell lifts, 5 for legs), and if not, it aims for one more rep, two for beginners. You can see how everything is logged in the workout tracker and how it is used day to day with the gym workout app. If you wonder how long to rest between sets so your RIR holds up, read the guide on rest between sets. The app is in Spanish only for now.