Can easing into failure match always pushing to the limit? A new study tested constant vs. progressive RIR to see how effort shapes gains and fatigue.
Overview
- What did they test? Researchers compared two training styles in resistance-trained men: always staying close to failure (~1 RIR) versus starting further from failure (4 RIR) and progressively closing the gap to 1 RIR. They measured strength, muscle growth, perceived exertion, and RIR accuracy.
- What did they find? Both groups improved strength and muscle size to a similar degree. Bench press 1RM rose by about 7–10% and squat 1RM by about 9–10%, while quadriceps CSA increased by 5–7% in both groups. Only the progressive RIR group showed a significant gain in triceps thickness. Training volume was comparable, but perceived exertion was lower when RIR was gradually reduced.
- What does it mean for you? Changing how close you train to failure doesn’t seem to boost short-term strength or muscle growth, but it can make workouts feel easier. RIR is already a reliable tool for trained lifters, and practicing it may make you even better at judging effort.
What’s The Problem?
Resistance training adaptations are strongly influenced by effort, but how close one must train to failure remains debated. Traditional percentage-based prescriptions (%1RM) do not account for individual variability in repetitions to failure, often leading to mismatches in actual training intensity. Repetitions-in-reserve (RIR) is a practical autoregulation tool, allowing lifters to gauge effort more precisely on a set-by-set basis.
Training to muscular failure is thought to maximize motor unit recruitment, particularly of high-threshold type II fibers, but recent evidence shows that near-failure training can achieve similar results as non-failure. For instance, Refalo et al. (2024) found that training to failure and stopping short produced nearly identical muscle growth 1. In studies that did not equate training volume between the groups, Grgic et al. (2022) showed significant favoring of non-failure training on strength gains. In another subgroup analysis for resistance-trained individuals, they found a significant effect of training to failure for muscle hypertrophy 2. Research using velocity-based training has shown that avoiding failure can result in comparable strength and power adaptations and the same muscle growth 3.
What remains less understood is whether systematically varying proximity-to-failure across a training cycle provides any unique advantage. Some coaches advocate beginning a block further from failure and progressively closing the gap, arguing this strategy balances fatigue management with progressive overload. Yet, despite its popularity in applied settings, direct evidence is sparse. The present study by Martikainen et al. (2025) addresses this gap by comparing a constant RIR approach (always ~1 RIR) with a progressive scheme (4 → 1 RIR across ten weeks). By examining outcomes in muscle hypertrophy, maximal strength, perceived exertion, and RIR accuracy in resistance-trained individuals, the study offers new insight into whether varying RIR meaningfully enhances adaptations or simply represents another way to achieve the same results.
Purpose
The study aimed to compare the effects of varying versus constant proximity-to-failure on muscle strength, hypertrophy, perceived exertion, and RIR estimation accuracy in resistance-trained individuals.
Hypothesis
The authors did not state a specific hypothesis.
