More sets keep building muscle, but strength gains flatten out much sooner

Weekly set volume and training frequency are the two main dials lifters turn to manage how much resistance training they do. Earlier research had already linked higher weekly volume with greater muscle growth and strength, but the actual shape of that relationship, whether gains keep climbing or level off, remained unclear. Evidence on frequency was even messier, with mixed results on whether spreading work across more days helps at all. Getting the dose right matters because time and recovery are finite, and wasted sets carry a real cost.

The researchers pooled 67 studies covering 2058 participants, 79.1% male and 20.9% female, with an average age of just over 25 years. Before analysing, they classified every training set as direct or indirect depending on how specific it was to the muscle or strength test being measured, then compared different ways of counting indirect work. Counting indirect sets as half a set, the fractional method, had the strongest evidential support and anchored the main models. A series of multi-level meta-regressions then mapped volume and frequency against hypertrophy and strength, adjusting for study duration and training status.

For weekly volume, the probability that more sets meant more muscle and more strength was 100%, but both relationships showed diminishing returns, and the flattening was considerably more pronounced for strength. In other words, size kept responding to added volume more steadily than strength did. Frequency told a different story: for strength, gains increased with more frequent training, again with diminishing returns, while for hypertrophy the frequency effect was compatible with being negligible. The authors also concluded that distinguishing direct from indirect sets appears essential for predicting what a given programme will deliver.

This work confirms the established finding that higher weekly volume drives greater adaptations, and extends it by describing the shape of the curve rather than just its direction. It also helps resolve the long-standing confusion around frequency by separating its effects on strength, which were consistently identifiable, from its effects on size, which were not. The participants were mostly young and mostly male, so how far these curves generalise to older lifters or to women remains open. So does the question of exactly where an individual's returns diminish.

If muscle size is the goal, this is a reason to think total weekly sets matter more than how many days those sets are spread across. If strength is the goal, both levers move the needle, but piling on ever more volume pays off less and less, and quite quickly. It also suggests that how you count sets matters: work that indirectly trains a muscle appears to contribute roughly half as much as work that targets it directly. None of this pinpoints a magic number of sets, and the right dose still depends on the person.