TRAINING PRINCIPLES
Proximity to failure (RIR)
RIR means reps in reserve. Zero is failure; 2 means you stopped with two reps still available.
The short answer
Tailrep's programs target 2-3 RIR on compound lifts and 0-2 RIR on isolation work. No set is designed to end at absolute failure.
What the research shows
- Refalo et al. (2023) found no evidence that training to momentary failure beats stopping short for hypertrophy (effect size 0.12, 95% CI -0.13 to 0.37).
- Robinson et al.'s (2024) meta-regressions found strength gains essentially flat across a wide range of RIR, while hypertrophy increased as sets ended closer to failure.
- Grgic et al. (2022) concluded that training to failure isn't required for strength or size — though it isn't harmful either, and trained lifters saw a small hypertrophy benefit (effect size 0.15).
- Neither "it's wasted unless you fail" nor "failure is dangerous" matches what the evidence currently looks like.
How to apply it
- Stop compounds like squats and bench with 2-3 reps left. Quitting before form breaks keeps the next set, and the next week, intact
- Isolation work like lateral raises and curls can go near failure. The loads are light and recovery is quick
- Taking every set to failure costs you total sets. Trading volume for intensity hasn't been shown to pay off
Programs built on this principle
References
Limits of this evidence, RIR is self-reported, and less experienced lifters tend to overestimate what's left. Robinson et al. (2024) themselves note the exact relationship stays unclear given how RIR was estimated.
Refalo MC, et al. (2023) Sports Medicine
Influence of Resistance Training Proximity-to-Failure on Skeletal Muscle Hypertrophy: A Systematic Review with Meta-analysis
Robinson ZP, et al. (2024) Sports Medicine
Exploring the Dose-Response Relationship Between Estimated Resistance Training Proximity to Failure, Strength Gain, and Muscle Hypertrophy: A Series of Meta-Regressions
Grgic J, et al. (2022) Journal of Sport and Health Science
Effects of resistance training performed to repetition failure or non-failure on muscular strength and hypertrophy: A systematic review and meta-analysis