RIR (Reps in Reserve)

Formula

Example

If you squat 100 kg for 5 reps and feel you could have done 2 more, your RIR is 2 (RPE 8).

How Afitpilot Uses This

RIR feeds directly into the e1RM formula (Epley with RPE adjustment). A higher RIR (lower RPE) increases the estimated 1RM because it implies the weight was submaximal. We don't ask athletes to log RIR separately, it's derived from RPE.

Recommended RIR by context

Known Limitations

• •RIR accuracy depends entirely on RPE accuracy. The same issues with subjective reporting apply.
• •RIR estimation is particularly unreliable for sets of 15+ reps, where fatigue accumulates non-linearly and the sensation of "reps left" becomes harder to gauge.

What We're Improving

• Future

  Effective Sets (Hard Sets) Tracking

  Track sets taken within 0-3 RIR of failure separately from total sets. Research increasingly suggests that "hard sets" are a better predictor of hypertrophy stimulus than total volume. This would give a more nuanced view of training dose.

• Future

  Prilepin's Table as LLM Strength-Prescription Guardrail

  Validate LLM-generated strength sessions against Prilepin's reps-per-set / total-reps ranges for the implied %1RM (derived from targetRpe → RIR → e1RM). Two surfaces: a plan-generation guardrail that flags or corrects out-of-range prescriptions, and a post-session signal that compares actual sets × reps × estimated %1RM against the optimal range. Deferred until we have 20+ real LLM-generated weeks audited; a ~8% high-intensity overshoot rate on a small fixture set was borderline-but-too-small to act on.

Science Context

RIR-based RPE scales have become the standard in evidence-based strength programming. Research by Helms et al. (2016) validated that trained lifters can estimate RIR within 1-2 reps for compound movements, though accuracy decreases with higher rep sets and isolation exercises.

Related Terms

• AMRAPA conditioning format where you complete as many full rounds (or reps) of a prescribed set of movements as possible within a fixed time cap. AMRAP flips the usual work-then-rest structure: instead of a target number of rounds at an unknown pace, you fix the time and let the round count be the outcome, the score is the honest measure of how much work you produced.
• EMOMA conditioning format where you perform a prescribed set of reps at the start of every minute, then rest for whatever time remains before the next minute begins. EMOM trades AMRAP's pacing freedom for a forced rhythm, the clock, not your own judgement, decides when the next round starts.
• TabataA high-intensity interval format of 20 seconds of maximal effort followed by 10 seconds of rest, repeated for 8 rounds (4 minutes total per exercise). Tabata is one of the few interval structures with a specific named research study behind its exact timing, the 20/10 split isn't an arbitrary convention, it's what the original protocol tested.
• ChipperA long list of movements performed once through, front to back, in order, you 'chip away' at the list rather than repeating rounds. Chippers are the opposite structural choice from AMRAP or EMOM: instead of a short list repeated many times, it's a long list done once, usually against the clock for time.
• RPE (Rate of Perceived Exertion)A 1-10 self-reported scale measuring how hard a set felt. In strength training, RPE is anchored to "reps in reserve" (RIR): RPE 10 means you couldn't do another rep, RPE 8 means you had roughly 2 reps left, RPE 6 means about 4 reps in reserve.