How many reps, and how heavy

Two numbers cover most of what a busy adult needs to know.

Roughly 4 to 6 reps per set builds strength. Roughly 8 to 15 builds muscle.

That is the working framing used by Sebastian Oreb, the Australian strength coach, and it is a good place to start because it is simple enough to act on and correct enough to be worth acting on.

The research that confused everyone

Over the last decade a body of work has shown that muscle can be built across a much wider range than anyone assumed — anywhere from about 5 reps to about 30 — provided the set is taken close enough to failure.

A lot of people read that and concluded: reps don't matter.

That is not what it says.

What it says is that the hypertrophy outcome is surprisingly robust to rep range when effort is held constant. Those last five words are the entire finding, and they are the part that gets dropped.

The best rep range still depends on three things:

Your goal. Strength and size are related but not identical. Heavy low-rep work develops the neural side — how much force you can express — in a way that sets of twenty do not. If you want to be strong, train heavy sometimes.

The exercise. A set of twenty deadlifts is a fatigue event with a rounding back at the end of it. A set of twenty leg presses is fine. The rep range has to suit what fails first in that movement — which for most hinges is your spinal position, not your muscles.

How you perform the set. Twenty sloppy fast reps and twenty controlled ones are different stimuli with the same number attached.

The part everyone skips

"Close enough to failure" is doing enormous work in that sentence, and it is where most people's training quietly stops producing anything.

The practical instruction: finish each set with about two reps left in the tank. You should genuinely believe you could have done two more with good form — and not five more.

A set of ten that felt comfortable did almost nothing. This is the single most common reason someone trains for a year and does not change: not the program, not the split, not the exercise selection. The sets were too easy and nobody told them.

Why the free guides mostly sit at 8 to 10

The four-week guides use 3 sets of 8 to 10 for most movements, with deadlifts lower at 6 to 8.

For someone in their forties or fifties who has not trained consistently, muscle they do not currently have is worth more than a heavier single they cannot use. Sets of eight to ten also let you accumulate meaningful work with technique that holds together, and they are far more forgiving of the fact that nobody is watching your form.

The deadlift sits lower because, as above, the thing that fails first there is your back position.

Progression, in one rule

When you can complete every set at the top of the rep range with two reps still in reserve, add weight.

That is it. Not a percentage scheme, not a periodisation block, not an app. If 3 × 10 goblet squats at 16 kg now finishes with two clean reps left on every set, go to 20 kg and drop back to eights. Then climb again.

Two things follow from this that are worth stating.

The weight has to actually go up over four weeks. If it does not, you have been maintaining, which is a legitimate goal but not the one these guides are for.

Write it down. Not for discipline — for memory. You will not remember in six days what you lifted, and "roughly the same as last time" is how a year of maintenance disguises itself as training.

What about the days you are wrecked

Some sessions you will be short on sleep, short on time, or coming off a bad week. Train anyway, lighter, and finish. Two-thirds of a session at 80% effort keeps the habit and still stimulates something.

The people who make progress over years are not the ones with the best programs. They are the ones who kept turning up in the weeks the program did not fit.