How hard you train
Reps in reserve (RIR)
Updated 6 August 2026
Reps in reserve, or RIR, is how many more reps you could have completed before failing. Stopping a set with two good reps left in you is two reps in reserve.
It is the most practical way to describe effort, because it survives a bad day. "Eight reps at 60kg" means something different when you are exhausted. "Stop two reps short" means the same thing every time.
How to judge it
Ask yourself at the end of a set: if someone offered you money, how many more reps could you have done with decent form? That number is your reps in reserve.
Most people are poor at this at first and improve quickly. The usual beginner error is overestimating: you think you had one left when you actually had four. Occasionally taking a set genuinely to failure recalibrates your sense of it.
- 0 in reserve means you could not have done another rep. That is failure.
- 1 to 3 in reserve is the productive working range for most sets.
- 4 or more in reserve is usually too easy to drive much adaptation, and is fine for warm-ups.
Why one to three is the sweet spot
Sets stopped one to three reps short of failure grow muscle about as well as sets taken to failure, and cost far less recovery. That trade is the entire argument. You keep almost all the benefit and hand back most of the fatigue.
It is also much safer. The reps closest to failure are where form falls apart, and form falling apart under a heavy bar is how people get hurt.
The relationship to RPE
Reps in reserve and rate of perceived exertion measure the same thing from opposite ends. RPE runs from 1 to 10, where 10 is a set you could not add a rep to.
The conversion is simple: reps in reserve is roughly ten minus your RPE. Two reps in reserve is about RPE 8.
In your plan
How Ionik Coach uses RIR
Ionik Coach programmes every working set with a reps in reserve target, usually between one and three depending on the lift and your goal, so sets are hard enough to work without being a gamble.
You never have to learn the term. After a set you tap a plain-language chip such as "felt great" or "too heavy", and that feedback is what the app reads. Any jargon the coach produces is rewritten before it reaches your screen, so "RIR 2" is shown as "stopping 2 reps before failure".
Common questions
Do I have to know my reps in reserve to use the app?
No. Ionik Coach asks how a set felt in plain words and works it out from there, along with the weight and reps you logged.
Is it bad if I misjudge my reps in reserve?
Not at all, and everyone does at first. Judgement improves with practice, and because the app also reads your actual logged weights and reps, one misjudged rating does not derail your plan.
Should every set have the same reps in reserve?
Generally the first sets of a lift sit slightly further from failure than the last, and heavy low rep work stays further from failure than lighter accessory work. Ionik Coach handles this per exercise.
Related terms
- Rate of perceived exertion (RPE) A 1 to 10 rating of how hard a set felt. It is the same idea as reps in reserve, counted from the other end.
- Training to failure Pushing a set until you physically cannot complete another rep. Useful occasionally, expensive as a default.
- Double progression Add reps until you fill the top of your rep range, then add weight and start again at the bottom. Two things progress, one at a time.
- Progressive overload Gradually asking your body to do more than it is used to. It is the one rule every training plan is built on.