A completed set can tell two different stories

Two people can lift the same weight for ten reps and experience entirely different demands. One may have five clean reps left; the other may barely complete the final repetition. Even your own response changes with sleep, food, stress, exercise order, and practice. Sets and reps describe what happened, but they do not fully describe how close the set came to your current limit.

That missing information matters when a plan says “three sets of ten.” If all three sets are effortless for weeks, the exercise may no longer provide the intended challenge. If every set becomes a grinding maximum, fatigue may outrun the value of the work. An effort scale adds context without requiring a true maximum test, a laboratory, or a dramatic end to every session.

Use RIR or set RPE for the set—not session RPE

Reps in reserve, or RIR, asks one concrete question at the end of a set: how many more technically acceptable repetitions could you have completed? The resistance-training-specific set-RPE scale encodes that same estimate in reverse. RPE 10 means zero RIR, RPE 9 means about one RIR, and RPE 8 means about two RIR. They are two labels for the same set-level judgment, not independent measurements.

Session RPE answers a different question: how demanding was the workout as a whole? It is typically recorded after the session and may be used to monitor overall training load. Do not convert a session score into reps remaining for one set. For day-to-day lifting decisions, choose RIR or RIR-based set RPE, record it immediately after the set, and keep the convention unchanged.

• Set RPE 6 or lower: roughly four or more clean repetitions remain.
• Set RPE 7–8: roughly three to two clean repetitions remain.
• Set RPE 9: roughly one clean repetition remains.
• Set RPE 10: no further clean repetition remains.

Calibrate with technique, not bravado

Rate the set immediately, then write down what made you choose the number. Did the final rep slow? Did the range shorten? Could you have repeated it without changing posture? On a safe, familiar exercise, you can occasionally continue one set slightly farther than usual to compare your estimate with reality. You do not need to do this on heavy, complex, or unsupported movements.

Your stop rule should include form. If you technically have another rep but it would require bouncing, twisting, or losing the intended range, that is not a clean rep in reserve. Video can sometimes help reveal a slowing repetition, but camera angle can also hide errors. An effort estimate becomes more useful when it agrees with observable movement rather than the emotion of the moment.

Count the repetitions you could repeat with the same technique—not every repetition you might force through.

Use effort beside the workout record

The development workout model stores exercises, sets, target reps, rest intervals, load, and completed sets. It does not yet persist a dedicated set-RPE or RIR field. Until that changes, treat effort as a deliberate end-of-set check and keep a short note outside the workout if the distinction will affect your next session.

A useful rule is to adjust one step at a time. If the planned work repeatedly finishes with four or more clean reps available, consider a modest progression. If the same load unexpectedly reaches one or zero, first check rest, sleep, exercise order, and technique rather than declaring the program broken. Future coaching features may use effort feedback, but they must never pretend an estimate is an objective measurement.

Sources

1. ACSM: Resistance training guidelines update (2026)
2. ACSM: Five things to know about an effective resistance plan
3. NSCA: Application of the repetitions-in-reserve-based RPE scale
4. Review: Session-RPE for monitoring overall training load