Closer to Failure, Bigger Muscles: What Science Says About RIR
New evidence shows strength can be built without going to failure, but hypertrophy may still benefit from taking your sets to the brink.
Do you wonder if pushing every set in the gym all the way to absolute failure is necessary for results, or if leaving a few reps “in the tank” works just as well? This recent meta-analysis directly tackles one of resistance training’s biggest debates: how close should you take your sets to failure for gaining the most strength and muscle possible?
Key Points
Study Aim
Purpose: Quantify the dose–response relationship between proximity to failure (repetitions in reserve, RIR) and outcomes in resistance training—specifically strength gains and muscle hypertrophy.
Methods
The researchers estimated RIR (how many reps short of failure each training set was) for dozens of studies, then used meta-regression to analyse outcomes for both muscle growth and strength.
The included data adjusts for training load, intervention duration, volume equating methods, and trainees’ experience.
Findings
Muscle Hypertrophy: The closer sets were taken to failure (lower RIR), the larger the increase in muscle size. Statistically, there was a meaningful negative slope: fewer reps left in reserve meant better muscle growth.
Strength Gains: Across a wide range of RIR—whether sets were stopped well before failure or just short of it—strength improvements were similar. In other words, training to failure made no meaningful difference for strength gains.
The statistical models fit best for muscle hypertrophy; results for strength were largely “null,” meaning proximity to failure didn’t move the needle.
