How long does it take to build muscle

Those are three different answers because it is three different questions, and that is why every page you have read gives you a different number. The rest of this page is what each one rests on, and what the change in your first fortnight actually is.

The short version

Your first fortnight is not muscle

In 2011 DeFreitas and colleagues put 25 sedentary men through 8 weeks of training and scanned their thighs every single week, which almost nobody does. After two sessions, the thigh was already 3.46% bigger.

Two sessions. Muscle does not build that fast, and the researchers did not claim it had. They wrote that muscular oedema may have influenced the result, adjusted for it, and concluded that real growth probably began somewhere around weeks 3 to 4.

So the early number is real, and it is fluid. A muscle you have just trained hard is damaged, and damaged tissue holds water. That is what the tape measure is picking up, and it is why an honest answer to this question has to say what it is measuring before it says when.

When the growing actually starts

The clearest evidence comes from Damas and colleagues in 2016, who took muscle biopsies from 10 young men at the start of training, at 3 weeks and at 10 weeks.

The muscle-building signal was at its highest in week 1, and it was not related to growth at all. Muscle damage was also at its highest in week 1. From week 3 onward, once that damage had settled down, the same signal tracked growth closely. Fibre size itself had only increased by the 10 week measurement.

Read that the right way round and it is encouraging rather than discouraging. The first few weeks are not wasted and they are not nothing. They are the weeks that settle the damage down, and until that happens your body is spending its effort on repair instead of on growth.

Strength moves first, and by a long way

In 2007 Seynnes and colleagues tracked 7 volunteers through 35 days. Muscle size rose significantly by day 20. Force rose 38.9%.

Put those together and the gap is the point: nearly 39% more force against a muscle about 7% bigger. Most of what you gain early is your nervous system learning to use the muscle you already have, not new muscle.

The same study found something even earlier. The length of the muscle fibres had changed by day 10, before any change in size showed up at all. The muscle reorganises before it grows.

One caveat the page will not skip: that trial used a flywheel machine rather than free weights, and its own authors say flywheel training seems particularly good at producing these early changes. Treat its timings as a best case.

Your muscles are not on one clock

The question assumes there is one answer for you. There is not, and the clearest demonstration is the only trial here that used free weights rather than a machine.

In 2012 Ogasawara and colleagues had 7 untrained men bench press three times a week for 24 weeks, scanning them with ultrasound every Monday. The chest thickened first. The triceps did not reach a measurable change until week 5. Strength moved at week 3, in between the two.

The biceps never changed at all. Not at 12 weeks, not at 24. Half a year of pressing three times a week moved that muscle precisely nothing. Worth knowing before you expect one lift to cover a body part it never loads.

One honesty note about that study. Its chest measurement reached significance after week 1, and that is the same week-1 reading the two trials above warn you about. We are not going to quote it as growth when the rest of this page explains why it probably is not. Read it as the chest responding earlier than the triceps, which is what it shows, rather than as a muscle built in seven days.

What to watch instead of the mirror

If strength moves first and size takes months, then the mirror is the slowest possible instrument for a question you want answered now. The log is the fast one.

• Write down what you lifted, every session. It is the only early evidence you have.
• Judge the first 4 weeks on whether the weight is going up, not on how you look.
• Give it 8 weeks before you conclude anything about size. Both trials that measured size properly were still measuring change at that point.
• If the weight has not moved in a month, the problem is the training, not the timeline.

This is the one place the site can help directly. The workout builder records what you lifted last time and shows it to you on the next session, which turns "is this working" into a number you can read. And if you want the other half of the answer, how long to wait inside the session rather than across the months, that is how long to rest between sets.

Common questions

How long does it take to build muscle?

It depends which of three things you mean. Strength starts moving in about 4 weeks. Actual muscle size becomes measurable on a scanner at around 3 to 4 weeks. Size you can see in a mirror takes months, and no study here measured that, so nobody can give you an honest week number for it.

Why do people say you see results in 2 weeks?

Because a muscle measured 2 weeks into training genuinely is bigger, and it is bigger because it is damaged and holding fluid. One study recorded a 3.46% increase in thigh size after only two training sessions. That is not growth, and the researchers said so themselves.

Will working out three times a week build muscle?

Yes. Every trial on this page trained people two or three times a week and all of them produced measurable change. The frequency is not usually what holds people back, the number of weeks is.

How long does it take to fully develop muscle?

Nobody can date a finish line, and no study here looked for one. What has been measured is 24 weeks of bench pressing three times a week. The chest thickened first, the triceps from week 5, and the biceps not at all. There is no single finish line even within one person.

Is a 30 minute workout enough to build muscle?

Length is not what the research measured. What it measured was weeks of consistent training, and the sessions in these trials were ordinary. A 30 minute session you do for 3 months beats an hour you do for 3 weeks.

Do all your muscles grow at the same rate?

No, and not even on the same exercise. In one 24 week study of free-weight bench pressing, the chest thickened measurably in the first weeks and the triceps only from week 5, in the same men doing the same lift. The biceps, which pressing does not train, did not change at all.

How can I tell it is working before I can see it?

Watch the weight on the bar rather than the mirror. Strength moves first and by a long way: one study measured force up almost 39% while muscle size went up about 7%. If the number you lifted last week is going up, it is working.

What is the fastest way to speed up muscle growth?

Nothing on this page will let you skip the weeks. What the research does say is that the early sessions are not wasted. They are not growing muscle yet. They are what settles the damage down, so that later training can.

Where these numbers come from

Every figure on this page comes from one of 4 papers. We store the fetched record for each one, so the author list and the population you are reading are the ones the paper actually has.

• Damas F, Phillips SM, Libardi CA and colleagues, 2016. Resistance training-induced changes in integrated myofibrillar protein synthesis are related to hypertrophy only after attenuation of muscle damage. The Journal of Physiology 594(18):5209 to 5222. 10 young men, biopsied at the start, at 3 weeks and at 10 weeks.
• DeFreitas JM, Beck TW, Stock MS, Dillon MA, Kasishke PR, 2011. An examination of the time course of training-induced skeletal muscle hypertrophy. European Journal of Applied Physiology 111(11):2785 to 2790. 25 healthy sedentary men, 8 weeks, scanned weekly.
• Seynnes OR, de Boer M, Narici MV, 2007. Early skeletal muscle hypertrophy and architectural changes in response to high-intensity resistance training. Journal of Applied Physiology 102(1):368 to 373. 7 young healthy volunteers, 35 days, flywheel ergometer.
• Ogasawara R, Thiebaud RS, Loenneke JP, Loftin M, Abe T, 2012. Time course for arm and chest muscle thickness changes following bench press training. Interventional Medicine and Applied Science 4(4):217 to 220. 7 untrained young men, free-weight bench press, 24 weeks, scanned weekly.

What this page does not claim: a rate of gain in pounds or kilograms, or anything at all about diet and protein. It does not claim beginners gain faster than trained lifters, and it makes no claim about age or sex. It does not claim the biceps cannot be grown, only that pressing did not grow them. Every population above was male. Three of the four studies had seven to ten people in them. None measured what a person can see rather than what a scanner reads, and none measured what anybody ate.

If a lift hurts rather than being hard, stop and see a physiotherapist.