Training close to failure grows muscle but adds no extra strength

How close to failure a set should go is one of the most argued questions in the gym. Grinding every set to the last possible rep is fatiguing and hard to recover from, so lifters want to know what stopping a few reps short actually costs them. Previous pooled analyses had only compared training to failure against not to failure as two crude categories. What nobody had done was treat proximity to failure as a sliding scale and ask how strength and muscle growth change across the whole range.

The researchers quantified proximity to failure as repetitions in reserve, the number of reps a lifter could still have performed when the set ended. Because most studies do not report this directly, the team estimated it from the descriptions of each training intervention. They then ran a series of multilevel meta-regressions on outcomes for both strength and muscle hypertrophy, adjusting every model for load, how volume was equated, the length of the intervention and the training status of participants, alongside a range of sensitivity analyses.

For strength, the best-fitting models showed a negligible relationship: gains were similar whether sets stopped well short of failure or very close to it. For muscle hypertrophy the picture was different, with every best-fitting model showing that muscle size increased more as sets were terminated closer to failure. The overall quality of model fit was described as modest, and the authors stress that because repetitions in reserve were estimated rather than measured, the exact shape of the relationship remains unclear.

This extends earlier work that could only say failure versus not failure, by mapping the dose-response curve across the whole spectrum. It supports a growing view that strength and size respond to different levers: strength appears forgiving of stopping early, while growth seems to reward pushing nearer the limit. The open questions are real, though. Estimated repetitions in reserve are imprecise, the analysis was exploratory by design, and the authors call for large studies built specifically to test this continuous relationship.

If your main goal is getting stronger, this is a reason to think you are not leaving much on the table by finishing sets with a few reps in reserve, which may also make training easier to recover from. If your main goal is muscle size, it is a reason to think proximity to failure matters more, with growth improving as sets end closer to the limit. Neither conclusion is final: the underlying estimates were rough, and the authors themselves urge caution until purpose-built studies confirm the pattern.