TLDR: For building muscle, progressing by adding weight or by adding repetitions at the same weight produce similar results over a training block of eight to ten weeks. For maximum strength specifically, adding load tends to have a small edge, though in controlled studies that edge is often too small to be considered practically meaningful. Most lifters can use either approach, or combine them, without compromising results.
What the research says
A 2022 study by Daniel Plotkin, Brad Schoenfeld, and colleagues, published in PeerJ, randomly assigned 43 resistance-trained adults to one of two eight-week protocols on the back squat, leg extension, and calf raises. One group increased the load they lifted while holding their repetition range steady. The other group held the load steady and increased repetitions instead. At the end of the study, rectus femoris muscle thickness increased slightly more in the group that progressed reps, by about 2.8 millimeters more than the load group, though the confidence interval ran from a small negative effect to a larger positive one. One-rep max squat strength moved modestly in favor of the load group, by about 2 kilograms, again with a confidence interval wide enough to include the possibility of no real difference. Across most other measures, quadriceps and calf muscle thickness, jump height, and body composition, the two groups looked essentially the same.
A separate 2024 study by Thiago Chaves and colleagues, published in the International Journal of Sports Medicine, used a within-subject design, meaning each participant’s own two legs were assigned to different conditions, removing much of the individual variation that complicates between-group comparisons. Thirty-nine previously untrained participants trained one leg with load progression and the other with rep progression on the leg extension for ten weeks. Both legs showed statistically indistinguishable increases in one-rep max strength and in vastus lateralis cross-sectional area measured by ultrasound. The load-progression leg lifted heavier weights throughout the study, as expected, while the rep-progression leg accumulated roughly 292 more total repetitions over the ten weeks. Despite that difference in how the work was done, the outcomes converged.
Why the method seems to matter less than expected
The likely explanation is that both approaches accomplish the same underlying task: they force a muscle to do more work than it did the session before, whether that additional work comes from a heavier load or from squeezing out more repetitions at a given load. Current evidence on loading ranges more broadly supports this. Research summarized by Brad Schoenfeld and colleagues has shown that similar hypertrophy can occur across a wide span of repetition ranges, from as few as five to more than thirty, provided sets are taken close to failure. If the muscle does not particularly care what rep range produced the effort, it makes sense that it would not care much whether that effort was reached by adding weight or adding reps either.
Strength appears to be the exception, and even there the case is not overwhelming. The theoretical argument for load progression having some advantage is specificity: a one-rep max test is itself a measure of moving a very heavy load, so training with heavier loads should transfer more directly to that skill. Both studies found the numbers trending in that direction, but in neither case was the difference large enough to describe as a clear practical advantage.
The practical takeaway
For hypertrophy-focused training, either method of progression works, and alternating between them across a training block, adding reps within a target range and then adding weight once the top of that range is reached, sometimes called double progression, is a reasonable way to use both without having to choose one exclusively. For lifters specifically training toward a strength goal like a heavier one-rep max, prioritizing load progression on the primary lifts makes sense given the specificity argument, even though the measured advantage in controlled trials has been modest.
This sits alongside two other pieces on OUTWRQ. Weekly Sets Per Muscle for Hypertrophy covers the volume side of the growth equation, and Do You Need to Train to Failure, or Is Leaving Reps in Reserve Enough? covers the effort side. Progressive overload is really the third leg of that stool: volume and effort determine whether a session is productive, and progression over time determines whether a program keeps producing results months from now.
Tracking which lifts are progressing by load and which are progressing by reps, across dozens of exercises and months of training, is exactly the kind of bookkeeping that gets lost without a log. OUTWRQ records both automatically session to session, which makes it easier to see at a glance whether a lift has actually been trending upward, and by which method, rather than relying on memory of what happened a few weeks back.
Written by the OUTWRQ team. Published August 2026.