How close to failure should I train?
Stop most sets 1–3 reps short of failure; going all the way adds fatigue for little or no extra growth.
Growth tends to increase a little the closer you get to failure, while strength gains look similar across a wide range, so the closer end suits muscle and the further end suits heavy strength work.
Judging RIR takes practice: most people think they are closer to failure than they are, by about one rep, and guesses improve near the end of a set. Taking the last set of an isolation exercise to true failure now and then calibrates the feeling; heavy squats and deadlifts are a poor place to do it.
Compare
Sources
5
- Refalo, M.C. et al. (2023). Influence of Resistance Training Proximity-to-Failure on Skeletal Muscle Hypertrophy: A Systematic Review with Meta-analysis. Sports Med 53(3). Momentary failure gave no clear extra muscle growth over stopping short.
- Zourdos, M.C. et al. (2016). Novel Resistance Training-Specific Rating of Perceived Exertion Scale Measuring Repetitions in Reserve. J Strength Cond Res 30(1). The RIR-based RPE scale used to judge proximity.
- Grgic, J. et al. (2022). Effects of resistance training performed to repetition failure or non-failure on muscular strength and hypertrophy: A systematic review and meta-analysis. J Sport Health Sci 11(2). No overall difference in strength or size; in trained lifters, failure gave slightly more growth.
- Robinson, Z.P. et al. (2024). Exploring the dose-response relationship between estimated resistance training proximity to failure, strength gain, and muscle hypertrophy: a series of meta-regressions. Sports Med 54(9). Muscle growth increased as sets ended closer to failure; strength gains were similar across a wide range.
- Halperin, I. et al. (2022). Accuracy in predicting repetitions to task failure in resistance exercise: a scoping review and exploratory meta-analysis. Sports Med 52(2). People underpredicted reps left by about one on average, regardless of training status.