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RPE (effort 1–10) and RIR (reps left in the tank) are the effort fields that turn a load×reps log into an auto-regulatable one.
RPE (Rate of Perceived Exertion) in resistance training usually uses a 1–10
repetition-based scale: RPE 10 = no more reps possible, RPE 9 = one more rep, RPE 8 = two
more, and so on. RIR (Reps In Reserve) is the inverse statement of the same thing —
RIR 0 = failure, RIR 2 = could have done two more. They are interchangeable: RPE ≈ 10 − RIR.
Why log it: load and reps alone do not capture how hard a set was. 100 kg × 8 at RIR 4 and at RIR 0 are very different doses despite identical training-volume-load. Recording effort lets the program:
Limitations: RPE/RIR rating accuracy improves with experience; novices tend to underrate effort (think they have more reps left than they do). Calibrate against occasional sets taken genuinely to failure. For cardio, a different (often Borg 6–20 or 0–10 session) RPE is used — see cardio-rpe.
Educational content only — not medical advice. Always consult a qualified professional for individualized guidance, especially around injury, pregnancy, or medical conditions.