RIR and RPE: how to measure effort in each set

Two sets of 80 kg × 8 repetitions can end very differently. In one, the athlete could complete several more repetitions. In the other, the eighth repetition is already at their limit.

The recorded load and repetitions are identical, but the remaining capacity differs. RIR and RPE add that context and help describe how much effort a set is intended to demand.

RIR: the repetitions left in reserve

RIR means repetitions in reserve. It estimates how many additional repetitions you could have completed while maintaining the agreed technique and range of motion.

• 3 RIR: you estimate that you could have completed three more repetitions.
• 1 RIR: you estimate that only one remained.
• 0 RIR: no complete repetitions remained under that standard.

This is an estimate, rather than a count of repetitions you have actually tested. Coach and athlete should therefore agree on what counts as a valid repetition. If one accepts a shorter range of motion and the other does not, they may assign different RIR values to the same set.

RPE: perceived exertion

RPE means rating of perceived exertion. Strength training commonly uses a scale up to 10 to communicate how demanding a set felt.

It can be practical for heavy lifts with few repetitions. After a 200 kg deadlift, an athlete might describe the set as very demanding without being equally confident about how many more repetitions they could have completed.

Agree on the meaning of the scale before using it. A number without a shared standard provides less information than it appears to.

RPE 8 and 2 RIR: a reference is not a guarantee of accuracy

Some RPE scales are explicitly based on RIR. Under that convention, RPE 8 is defined as roughly two repetitions in reserve, RPE 9 as one and RPE 10 as none. The study by Zourdos and colleagues describes this strength training scale.

That relationship defines how effort is communicated; it does not guarantee that the athlete estimated their capacity exactly. A general effort rating should also not automatically be converted as though it always used that RIR-based scale.

Accuracy depends on context. A study of RIR estimation found differences associated with proximity to failure and the repetitions performed. Treat the record as a useful estimate with limitations.

Choose the standard according to the exercise

During a set of 12 curls, thinking about how many valid repetitions remained may feel more intuitive. During a heavy lift, communicating effort through RPE may be easier.

This is a practical suggestion, rather than a universal rule. Consider the exercise, load and athlete’s experience. What matters most is that the person prescribing the work and the person performing it interpret the value in the same way.

Record what happened, even when it differs from the plan

If the plan called for 2 RIR and the set ended at 0 RIR, the result should show 0 RIR. Recording the target as though it were the outcome hides a difference that may matter for the rest of the session and the next training plan.

Recording that difference makes it possible to review whether load, volume or recovery should change. If it repeatedly goes unrecorded, the coach may keep making decisions based on capacity the athlete did not have.

Plan effort and keep the actual outcome. The scale is valuable because of the context it provides for deciding what to do next.