Nearly every certification syllabus teaches some version of the same chart. Low reps with heavy loads build strength and power. Moderate to high reps with moderate loads build muscle size. High reps with light loads build local endurance. The IFPA text follows this structure closely, mapping a preparatory hypertrophy phase to roughly 15-repetition sets, a strength phase to 8 to 10, and a power phase to 1 to 6.
As a teaching device the chart is genuinely useful, and one half of it has held up well under a decade of scrutiny. The other half has not survived, and the way it failed is more interesting than a simple correction — because it hands working trainers considerably more freedom than they were taught they had.
What has held up: strength is load-specific
The strength side of the chart is in good shape. When training volume is equated, heavier loads produce superior gains in maximal dynamic strength. This is exactly what the specificity principle predicts: getting stronger at a lift is substantially a skill, and skills are practised at something close to the conditions in which they are expressed. A client who wants a bigger squat has to squat heavy, reasonably often.
Recent work has sharpened this rather than overturned it. A large 2026 meta-regression in Sports Medicine by Pelland and colleagues, pooling 67 studies and just over 2,000 participants, found that weekly training frequency showed a consistent benefit for strength — more exposures to the lift, more strength — while showing negligible effect on muscle growth. Strength behaves like a practised skill, and it responds to practice.
What has not: hypertrophy is largely load-agnostic
The hypertrophy half is where the chart misleads. Schoenfeld and colleagues' 2017 meta-analysis in the Journal of Strength and Conditioning Research compared training above and below 60 per cent of one-repetition maximum and found essentially no difference in whole-muscle growth between them. The difference in effect size was 0.03, with confidence intervals narrow enough to make the conclusion difficult to argue with: as a standalone variable, load is not what drives muscle growth.
That finding sounds implausible until you ask what load was standing in for. Heavier weights force high effort quickly. Lighter weights only do so if you keep going. When the sets are taken to a comparable degree of effort, the growth stimulus turns out to be comparable too — and load was never the active ingredient, only a convenient way of guaranteeing it.
What actually drives growth: effort and volume
The active ingredients look like proximity to failure and total hard sets. Robinson and colleagues' 2024 series of meta-regressions in Sports Medicine examined how close to failure sets were taken, expressed as repetitions in reserve, and found a clean dissociation between the two goals: muscle growth increased as sets were taken closer to failure, with the benefit flattening out somewhere around two repetitions in reserve, while strength gains were largely indifferent to how close to failure the training went.
Volume behaves differently between the two as well. The Pelland meta-regression found that both size and strength improve as weekly sets increase, but with markedly different shapes: diminishing returns set in far more sharply for strength than for hypertrophy. Adding sets keeps paying for muscle growth long after it has stopped paying for maximal strength.
Put those together and the two adaptations pull apart cleanly. Growth responds to hard sets, accumulated in reasonable volume, taken near enough to failure to matter — and is relaxed about load and about frequency. Strength responds to heavy, specific, frequent practice — and is relaxed about grinding every set to failure.
One mechanism worth retiring
Older texts, IFPA's among them, explain bodybuilding-style growth through sarcoplasmic hypertrophy: high-volume training accumulates lactic acid, the cell takes on fluid, and the muscle 'volumises' into a larger but less dense structure. It is a memorable story and it appears in a great many syllabi.
It has not aged well. A 2020 review in Frontiers in Physiology by Roberts and colleagues, pointedly subtitled with the question of whether sarcoplasmic hypertrophy is a scientific unicorn or a real training adaptation, concluded that while changes in sarcoplasmic content are plausible and have some support, there is no good evidence that it is a distinct adaptation a trainer can deliberately switch on with a particular rep range. The lactic-acid mechanism in particular does not hold up; lactate is a fuel and a signal, not the villain of the older account.
The practical consequence is small but real: do not program a client's training around producing a specific kind of muscle. Program around effort, volume and progression, which are the variables the evidence actually supports.
Resist rebuilding your programme every time a paper lands
It is worth modelling some restraint here, because the same literature that corrects the rep-range chart also produces findings that reverse. Training the stretched portion of a movement — lengthened partials — looked like a meaningful hypertrophy advantage in a 2023 meta-analysis, with a small but real effect favouring it. By 2025, with more studies pooled, the advantage over full-range training had largely evaporated, and the honest summary is that the two approaches perform about the same.
Full range of motion remains a perfectly good default, and a trainer who had rebuilt every client's programme around lengthened partials in 2023 would have spent two years chasing a finding that did not hold. Weight a conclusion by how much evidence sits behind it, and treat a single striking study as a reason to pay attention rather than a reason to act.
What this changes on the gym floor
The load-agnostic finding is the one that changes real sessions, because it converts a constraint into an option. A client with a cranky shoulder, an office worker who trains at home with light dumbbells, an athlete in season who cannot afford heavy spinal loading, an older client who finds heavy barbells intimidating — none of them are excluded from building muscle. They need enough hard sets taken close enough to failure, not a heavier bar.
- Chasing size: enough hard sets per muscle each week, most taken within about two repetitions of failure, load chosen for what the client and their joints tolerate
- Chasing strength: heavier loads on the specific lifts that matter, more frequent practice, and no need to take every set to failure
- Chasing both, which is most general clients: heavy specific work early in the session, higher-repetition accessory work after it
- Progress the variable you are actually training — load and repetitions for strength, hard sets and effort for size
- Record proximity to failure alongside sets and reps, or you are not tracking the variable that drives growth
It also reframes a conversation trainers have constantly. A client who says they want to get toned and not bulky, and a client who wants to get as strong as possible, are not asking for different rep ranges so much as different priorities in the same programme. Both will be lifting weights near enough to failure to matter. What changes is how heavy, how specific, and how often.
A note for exam candidates
As with any place the research has moved past the syllabus: on the IFPA certification test, answer according to the textbook. The exam is assessing the syllabus. Understanding where the evidence has since gone is what makes you a better coach afterwards, and the two goals do not conflict as long as you keep them straight.
The bottom line for trainers
The rep-range chart is half right, and it is worth knowing which half. Strength is specific and load-driven, so train it that way. Muscle growth is driven by hard, sufficiently frequent effort across a broad spectrum of loads, which means you can build it around whatever equipment, joints and confidence your client actually brings. That is a more flexible, more forgiving picture than the chart implies — and being able to explain it to a client in plain language is exactly the kind of programme-design judgement the PFT seminar's exercise prescription phases are built to develop.