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Randomized trialProximity to failure
Cardiac rehabilitation patients were randomly assigned to load prescribed by a reps-in-reserve rating of perceived exertion or by a percentage of estimated one-rep max, with everything else matched. Strength rose in both groups with no between-group difference and trivial effect sizes either way.
How Fibral applies it: Where a one-rep max is unavailable or unsafe to test, prescribe by reps in reserve without expecting a worse outcome.
Limits and applicability
No limitation statement has been published for this note yet. Treat it as a general evidence-informed rule, not an individualized guarantee.
- Gismondi A, Iellamo F, Caminiti G, Sposato B, Gregorace E, D'Antoni V, Di Biasio D, Vadalà S, Franchini A, Mancuso A, Morsella V, Volterrani M. (2024). Rate of Perceived Exertion Based on Repetitions in Reserve Versus Percentage of One-Repetition Maximum for Resistance Training Prescription in Cardiac Rehabilitation: A Pilot Study. View source
Approved content v1 · updated Aug 17, 2026
Expert consensusProximity to failure
A methods review argues that using reps in reserve on its own assumes identical RIR values correspond to equivalent physiological stimuli across different repetition ranges and intensities, an assumption that does not necessarily hold. It proposes a proportion-based level of effort, the share of a set's repetition capacity actually used, as a more complete description.
How Fibral applies it: Do not read the same RIR target as the same dose across very different rep ranges; anchor it to a load or a rep target as well.
Limits and applicability
No limitation statement has been published for this note yet. Treat it as a general evidence-informed rule, not an individualized guarantee.
- Pareja-Blanco F, Loturco I. (2026). Level of Effort: A Practical Approach for Resistance Training Monitoring and Prescription. View source
Approved content v1 · updated Aug 17, 2026
Expert consensusProximity to failure
A rating-of-perceived-exertion scale defined by how many repetitions remain at the end of a set is proposed as a more precise tool than a session-level rating. It adjusts load automatically to match the lifter's capability set to set and gauges intensity better at near-limit loads.
How Fibral applies it: Express set effort as reps in reserve and let the load float from set to set to hold that effort constant.
Limits and applicability
No limitation statement has been published for this note yet. Treat it as a general evidence-informed rule, not an individualized guarantee.
- Helms ER, Cronin J, Storey A, Zourdos MC. (2016). Application of the Repetitions in Reserve-Based Rating of Perceived Exertion Scale for Resistance Training View source
Approved content v1 · updated Aug 17, 2026
Randomized trialProximity to failure
In a randomized crossover comparing percentage-based, RPE, reps-in-reserve and velocity-based prescription at the same relative load, percentage-based prescription regularly drove sets to failure while reps-in-reserve and velocity-based prescription preserved training volume. No condition differed in next-day neuromuscular fatigue or soreness.
How Fibral applies it: Prescribe set effort as reps in reserve rather than as a fixed percentage of one-rep max, because a fixed percentage silently turns ordinary sets into sets to failure.
Limits and applicability
No limitation statement has been published for this note yet. Treat it as a general evidence-informed rule, not an individualized guarantee.
- Cowley N, Nicholson V, Timmins R, Munteanu G, Wood T, García-Ramos A, Owen C, Weakley J. (2025). The Effects of Percentage-Based, Rating of Perceived Exertion, Repetitions in Reserve, and Velocity-Based Training on Performance and Fatigue Responses. View source
Approved content v1 · updated Aug 17, 2026
Randomized trialProximity to failure
Older adults asked to stop at 2 and 4 reps in reserve underestimated the repetitions they had left by 2.1 and 1.6 reps, while a 6-rep-in-reserve target was accurate. The authors conclude that predicted RIR may lack precision for prescribing load but remains useful for monitoring volume.
How Fibral applies it: Expect a prescribed RIR close to failure to be met conservatively, and read RIR as a volume monitor rather than an exact load prescription.
Limits and applicability
No limitation statement has been published for this note yet. Treat it as a general evidence-informed rule, not an individualized guarantee.
- Gómez-Redondo P, Alcazar J, Valenzuela PL, Ara I, Alegre LM, Mañas A. (2025). Validity of repetitions in reserve for prescribing resistance exercise in older adults. View source
Approved content v1 · updated Aug 17, 2026
ObservationalProximity to failure
Experienced and novice lifters estimated 3 and 1 reps in reserve in the back squat at 70% of one-rep max with no difference in accuracy between the groups, corroborated objectively by mean propulsive velocity and rating of perceived exertion. The authors suggest familiarity with high-effort sets matters more than years of training.
How Fibral applies it: Do not gate reps-in-reserve prescription on training age; give a beginner an RIR target and spend the effort on familiarising them with hard sets instead.
Limits and applicability
No limitation statement has been published for this note yet. Treat it as a general evidence-informed rule, not an individualized guarantee.
- Droguett FAB, Festa RR, Quintana NAT, Gomez-Lopez J, Ojeda ÁH, Farias-Valenzuela C, Giakoni-Ramírez F, Jofré-Saldía E. (2025). Objective Accuracy in Estimating Repetitions in Reserve in the Back Squat: An Analysis between Experienced vs. Novice Subjects. View source
Approved content v1 · updated Aug 17, 2026
Meta-analysisProximity to failure
A series of meta-regressions treating proximity to failure as a continuous variable in reps in reserve found that strength gains were similar across a wide range of RIR, while muscle hypertrophy improved as sets were terminated closer to failure. The authors conclude the optimal proximity to failure may differ between the two outcomes.
How Fibral applies it: Take hypertrophy work closer to failure and leave more reps in reserve on strength work, because only size responds to how close a set finishes to failure.
Limits and applicability
No limitation statement has been published for this note yet. Treat it as a general evidence-informed rule, not an individualized guarantee.
- Robinson ZP, Pelland JC, Remmert JF, Refalo MC, Jukic I, Steele J, Zourdos MC. (2024). Exploring the Dose-Response Relationship Between Estimated Resistance Training Proximity to Failure, Strength Gain, and Muscle Hypertrophy: A Series of Meta-Regressions View source
Approved content v1 · updated Aug 17, 2026
Meta-analysisProximity to failure
A meta-analysis comparing sets performed to failure versus stopping short found no significant difference in strength or hypertrophy when training volume was equated. Training to failure increased perceived effort and fatigue without clearly superior adaptations.
How Fibral applies it: Do not make failure the default; stopping a rep or two short on most sets maintains gains while limiting fatigue and injury risk.
Limits and applicability
No limitation statement has been published for this note yet. Treat it as a general evidence-informed rule, not an individualized guarantee.
- Grgic J, Schoenfeld BJ, Orazem J, Sabol F (2022). Effects of resistance training performed to repetition failure or non-failure on muscular strength and hypertrophy: A systematic review and meta-analysis View source
Approved content v3 · updated Aug 17, 2026
Meta-analysisProximity to failure
A meta-analysis found only a trivial advantage for training to set failure over stopping short of it for hypertrophy, with no moderating effect of volume load or relative load, and no advantage at all when the comparison was restricted to momentary muscular failure. Higher velocity-loss thresholds, which are theoretically closer to failure, did not reliably produce more growth either.
How Fibral applies it: Take most working sets close to failure without routinely reaching it: the evidence does not support momentary muscular failure as a requirement for growth, and stopping short of it accumulates less fatigue for the same result.
Limits and applicability
No limitation statement has been published for this note yet. Treat it as a general evidence-informed rule, not an individualized guarantee.
- Refalo MC, Helms ER, Trexler ET, Hamilton DL, Fyfe JJ (2023). Influence of Resistance Training Proximity-to-Failure on Skeletal Muscle Hypertrophy: A Systematic Review with Meta-Analysis View source
Approved content v4 · updated Aug 17, 2026