Progressive overload: how to keep making progress

The idea behind progressive overload is old and simple: a muscle adapts to what you ask of it, so to keep adapting you have to keep asking a little more. Where people go wrong is in assuming that “more” means one thing — a heavier bar, every session, forever.

The evidence describes something broader and more forgiving. You can progress by adding weight, but also by adding reps, and for muscle growth the two work about equally well. Knowing which to do next, and when the load should finally go up, is most of the skill.

What progressive overload means

The American College of Sports Medicine’s 2009 position stand defines progressive overload as the gradual increase of stress placed on the body during training, and lists several ways to apply it: a heavier load, more total repetitions at the current load, changes to repetition speed, changes to rest periods, and more total volume. ¹ Heavier weight is one lever among several.

That matters because adding weight is not always available. Dumbbells jump in fixed steps, cable stacks in coarse ones, and on small exercises even the smallest step can be a large fraction of the load. Adding reps is always available — and, as the next section shows, it counts.

Adding sets is another lever, and the one with the most direct evidence behind it. Our guide to training volume covers how many sets that evidence supports; this article is about the session-to-session decision of what to change next.

Adding reps is progress

The most direct test of this is a 2022 trial that randomised 43 resistance-trained adults — 27 men and 16 women, averaging 23 years old — to one of two ways of progressing the same lower-body programme for eight weeks. ² One group kept the rep range at 8–12 and added load whenever they could; the other kept the starting load and added reps. Both trained twice a week, with sets taken to or close to failure.

Muscle growth was similar between the groups at nearly every site measured, and the one muscle that differed slightly favoured the reps group. ² Squat strength rose by roughly 20 kg in both; the load group’s gain was about 2 kg larger, but the uncertainty ran from about 8 kg in its favour to about 2 kg against, so the authors judged the difference of questionable practical importance. Their conclusion was that both progressions are viable strategies.

The study has the limits the authors list: young lifters, lower-body muscles only, eight weeks, and a strength test on a Smith machine after training with a free-weight squat. ² It is one trial, not a settled answer. But it is the cleanest evidence available that a lifter adding reps at a fixed weight is progressing, not standing still.

When the load has to rise

If reps work, why add weight at all? Because muscle size and strength respond to load differently.

A 2021 network meta-analysis pooled 28 studies and 747 healthy adults, all training with sets taken to failure, and compared light loads (more than 15 reps per set), moderate loads (9–15) and heavy loads (8 or fewer). ³ Muscle growth did not differ between them. Strength did: heavy and moderate loads both beat light loads, and heavy loads edged moderate ones, though that last difference was not statistically significant.

So the reason to progress the load depends on the goal. For muscle size, a hard set of 20 reps and a hard set of 8 appear to do similar work, which is why adding reps can carry you a long way. For strength, the load has to climb eventually — reps can build toward it, but a lifter who only ever adds reps drifts out of the heavier range where strength is built.

That is also why a rep range has a top. Reps rise until they reach it, then the weight goes up and the reps reset toward the bottom. This is often called double progression, and it captures both findings: reps carry the growth, and the range keeps the load heavy enough for strength.

How hard each set needs to be

Progress depends on effort, but not on maximal effort every set. ACSM’s 2026 position stand, an overview of 137 systematic reviews that updates the 2009 stand, concludes that completing sets to momentary muscular failure does not enhance gains in strength, size or power, so it is not necessary for benefits to occur. ⁴ Its central recommendation is that healthy adults perform progressive resistance training.

The research on proximity to failure fits that. A 2023 meta-analysis found only a trivial advantage for training to failure over stopping short when it came to muscle growth, and concluded there was no evidence that training to momentary failure is superior. ⁵ A 2024 analysis that estimated how many reps were left in reserve found muscle growth improved as sets ended closer to failure, while strength gains were similar across a wide range — but its authors call the work exploratory, because reps in reserve had to be estimated from study descriptions. ⁶

That points to a practical problem: nobody measures reps in reserve directly. A meta-analysis of prediction accuracy found people tended to underestimate how many reps they had left, by about one on average, with accuracy improving slightly closer to failure and in sets of 12 reps or fewer. ⁷ Researchers also lack a consistent way of measuring proximity to failure, and studies define failure itself differently, which makes precise targets hard to justify. ⁸

The workable reading is this: most sets should be hard — within a few reps of failure — without needing to reach it. And because “two reps in reserve” is a judgement rather than a measurement, it is better treated as supporting evidence than as the trigger for adding weight.

A working rule

ACSM’s 2009 stand gives the most-quoted progression rule: when a lifter can perform the current load for one or two reps beyond the target in two consecutive sessions, increase the load by 2–10%, using the lower end for small-muscle exercises and the higher end for large ones. ¹ It is a sensible rule, but worth seeing for what it is. ACSM graded it B — limited evidence — and it rests on a single 1999 paper. ¹ The percentages are practical guidance, not measured thresholds.

Our Progressive Overload Calculator turns that guidance into explicit rules, and labels them as implementation rules rather than science:

• The load goes up when every set reaches the top of your range with technique intact and no pain. Until then, the answer is more reps at the same weight.
• The increase is the smallest step your equipment allows that lands within a band for the type of exercise — 2.5–5% for large and moderate compound lifts, 2–5% for isolation exercises, and 1–2.5% for small ones like lateral raises, following ACSM’s advice to go lower on small-muscle exercises.
• When even the smallest step is too large — 15 to 20 lb dumbbells is a 33% jump — it keeps you adding reps, and allows the jump only once every set goes two reps past the top of the range.
• Pain or a breakdown in technique vetoes any increase, and severe pain stops the calculation entirely. No number of reps earns a heavier load through either.

The tool also asks for last session’s reps, optionally, because a rule like ACSM’s is about consistency across sessions, not one good day — and it says so when it has less to go on.

The bottom line

Progress is not the same as adding weight. Adding reps at the same load is progress, and for muscle growth it appears to work about as well. Load matters more for strength, which is why reps should eventually hand over to a heavier weight rather than climb forever.

Most of the time, train hard but short of failure, and treat your own sense of reps in reserve as a rough guide rather than a precise number. Add weight when every set has reached the top of your range, in the smallest step that makes sense for the exercise — and never let pain or failing technique be the price of a heavier bar.