RPE and RIR: How to Train by Effort Instead of Guesswork

Most programmes tell you to lift a set weight for a set number of reps. That works until real life gets involved: a short night of sleep, a stressful week at work, a cold, or a day where everything feels light. Rating each set by effort lets the plan bend with you. The two tools for that are RPE, the rating of perceived exertion, and RIR, reps in reserve.

The two scales in plain terms

Reps in reserve is the simplest idea in lifting: when you rack the bar, how many more clean reps could you have done? RPE for lifting uses a 1 to 10 scale built on the same question, so the two map onto each other.

RPE	Reps in reserve	What it feels like
10	0	Could not do another rep, or add any weight
9.5	0, maybe 1	No more reps, but slightly more weight was possible
9	1	One more rep, definitely
8	2	Two more reps
7	3	Bar moving quickly, three more reps
6 or below	4 or more	Warm-up territory

The scale was adapted for strength training by Mike Zourdos and colleagues in 2016, and it has since become standard in powerlifting coaching and in many hypertrophy programmes.

How close to failure you need to train

A 2023 meta-analysis by Martin Refalo and colleagues pooled studies on how proximity to failure affects muscle growth. Growth was similar across a fairly wide range, and sets that ended a few reps short of failure built nearly as much muscle as sets taken all the way. Strength tended to benefit from heavier loads more than from grinding to failure.

The practical lesson: you do not need to fail every set. Stopping one to three reps short on squats, deadlifts and presses keeps technique clean and lets you recover for the next session. Machines, cables and isolation exercises are safer places to push closer to zero.

Learning to rate honestly

Studies consistently find that lifters underestimate how many reps they have left, and the error grows with higher-rep sets. A set of 15 that feels like RPE 8 is often closer to RPE 6. Accuracy improves the closer you get to failure and the more experienced you are.

Three habits help:

• Calibrate occasionally. On a safe exercise such as a machine press or leg extension, take your last set to genuine failure and compare it with what you predicted.
• Watch bar speed. When a rep slows noticeably compared with the first one, you are usually within two or three reps of failure.
• Rate immediately. Write the number down before you sit down. Ratings drift once you have rested.

Using effort to set the weight

RPE turns a fixed programme into an adjusting one. A common pattern is a “top set” followed by back-off sets:

1. Work up to a single set of five at RPE 8.
2. Take 5 to 10 percent off that weight.
3. Do three more sets of five with the lighter load.

On a good day the top set will be heavier; on a bad day lighter. Either way you get the right training stress without guessing.

RPE and recovery from hard cycles of training

Effort ratings are especially useful when recovery capacity changes: during a calorie deficit, during illness, when travelling, or after a change in medication or hormones. Some lifters find their strength rises quickly while tendons and joints lag behind. Keeping most sets at two or three reps in reserve protects connective tissue while still producing progress.

Where effort ratings fall short

• They are subjective. Two people can rate the same set differently, so compare yourself only with yourself.
• They are less reliable for very light, high-rep work, where burning and breathing cloud the judgement.
• They do not replace a plan. RPE adjusts the weight; you still need a structure for exercises, sets and progression.

A simple way to start

For the next four weeks, keep your current programme but add one column to your log: the RPE of the last set of each exercise. Aim for 7 to 8 on big compound lifts and 8 to 9 on isolation work. Increase the weight whenever the last set comes in lower than planned. After a month you will have a much better feel for your own effort, and a record that shows when you are recovering well and when you are not.