Training to failure

Failure is RIR 0 and RPE 10: you can't get another rep. What matters for muscle growth is proximity to failure: a set where you could have done eight more grows muscle much worse than a hard one. But you don't have to go all the way to the edge.

In Grgic et al.'s 2022 meta-analysis of 15 studies, training to failure and not to failure produced similar gains in strength and muscle. In Refalo et al. (2023), muscle growth was close whether sets went to failure or stopped a few reps short — and failure added more fatigue.

A practical rule: keep most of your work 1–3 reps from failure and take only the last isolation set to failure, where it's safe. In a heavy squat or deadlift, failure is risk with no payoff. More on sets that do almost nothing in the junk volume guide.