How many reps in reserve (RIR) should you leave?

What RIR is, how close to failure you need to train, and why the answer changes if you want muscle or strength.

~4 min read·last reviewed September 2026·3 sources cited

From the same series: how many sets per muscle? · do you have to train to failure? · the whole series

Short answer: RIR is the number of reps you leave in the tank when you end a set. For muscle, closer to failure is better — but the gap between hitting failure and stopping one or two reps short is small¹. For strength, it barely matters². In practice: keep most sets between 0 and 2 RIR.

For hypertrophy

0–2 RIR

the closer a set is taken to failure the more you grow, with no point where it suddenly changes²

Failure vs. stopping short

trivial

across 15 studies, going to failure beats stopping short by a margin too small to notice¹

For strength

≈ nothing

training closer to or further from failure barely changes the strength you gain²

§1What RIR actually is

RIR stands for repetitions in reserve: the reps you could have done and didn't. Stop a set feeling like two more were there, and that set was 2 RIR. Zero RIR is failure: the next rep doesn't happen.

It is a way of measuring the effort of a set without depending on a percentage of your max, which moves from day to day. It became a scale in 2016, when a resistance-training-specific rating of perceived exertion was proposed based precisely on counting those reps in reserve³.

How to read these numbers: a meta-analysis pools the published studies on a question and re-analyses them together; a meta-regression goes one step further and looks for the shape of the relationship — not "is A better than B?", but "how much does the result change with how close to failure you train?". That is why the two papers cited here don't contradict each other: same question, different lens.

§2What the evidence says

In 2023, a systematic review with meta-analysis pooled 15 studies comparing training to failure against stopping short. The result: a trivial-sized advantage for failure in hypertrophy, and signs that the relationship between how close to failure you train and how much you grow is not a straight line¹.

In 2024, a series of meta-regressions took the same question continuously, estimating the RIR of each training programme instead of splitting the world into "failure / not failure". That is where the useful nuance showed up: hypertrophy increases the closer sets are taken to failure, while strength gains hardly change with how close to failure you train².

Both fit together: getting close to failure adds for muscle, and the last stretch — from 2 RIR to 0 — adds little and costs a lot in fatigue.

§3How to use it

If you train for muscle, most of your sets should land between 0 and 2 RIR. You don't need to fail on all of them: hitting failure on every set of every exercise doesn't buy proportional growth, and it does buy fatigue — paid back in the sets after it and in the session after that.

If you train for strength, stay further away: the evidence says how close to failure you train moves the needle very little, and technique degrades near the limit.

And an honest warning: estimating RIR is a skill. Early on, most people believe two were left when four were. It calibrates with time, and the fastest way to calibrate it is to take the occasional set to true failure — on something safe, a machine or an isolation movement — to remember where the limit actually is.

Why this needs an app

Estimating RIR is a skill, and a skill gets calibrated by comparing what you believed with what happened next. With no sets written down there is nothing to compare against.

What GymSets counts are hard sets: the ones done close to failure, which are the ones the literature ties to growth. You log the set, the app adds it to its muscle group and tells you how many you have this week for each one. Without that, "I do 15 sets of chest a week" is an estimate — and usually an optimistic one.

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§4References

Refalo, M. C., Helms, E. R., Trexler, E. T., Hamilton, D. L., & Fyfe, J. J. (2023). Influence of resistance training proximity-to-failure on skeletal muscle hypertrophy: a systematic review with meta-analysis. Sports Medicine, 53(3), 649–665. doi.org/10.1007/s40279-022-01784-y
Robinson, Z. P., Pelland, J. C., Remmert, J. F., Refalo, M. C., Jukic, I., Steele, J., & Zourdos, M. C. (2024). Exploring the dose–response relationship between estimated resistance training proximity to failure, strength gain, and muscle hypertrophy: a series of meta-regressions. Sports Medicine, 54(9), 2209–2231. doi.org/10.1007/s40279-024-02069-2
Zourdos, M. C., Klemp, A., Dolan, C., Quiles, J. M., Schau, K. A., Jo, E., Helms, E., Esgro, B., Duncan, S., Garcia Merino, S., & Blanco, R. (2016). Novel resistance training-specific rating of perceived exertion scale measuring repetitions in reserve. Journal of Strength and Conditioning Research, 30(1), 267–275. doi.org/10.1519/JSC.0000000000001049