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What is muscle memory and how long does it last?

Was ist das Muskelgedächtnis und wie lange hält es an?

Muscle memory is your body's ability to rebuild muscles that it had once built up. Studies show that muscle memory can last up to 15 years - maybe longer.

A few years ago, I had a friend who put a lot of time and effort into her fitness. She trained hard, ate well and made sure she got enough sleep. She also had a body that showed it. She could bench press more than most of the guys at her gym, she moved over 150 kilos doing squats and she had the body of a goddess.

But then she injured her lower back. The consequences? Three months of no training - neither weights nor cardio - just rehabilitation training. For someone like her, this was the ultimate punishment. She lost a lot of muscle mass, built up some fat and had to watch her bench press weights drop to 45 kilos.

But once she was back in the gym and able to train properly again, she regained her previous form in record time. While it had originally taken her seven years to achieve this form, she was now able to rebuild everything in a tenth of the time.

And no, she didn't know any "ancient Chinese secrets". What she experienced was the power of muscle memory. And you can experience this too.

What is muscle memory?

Muscle memory sounds good, doesn't it? Almost too good to be true. But this is one of those cases where things are as they seem. I'm sure you've heard the argument that bodybuilding is a thankless sport. As long as you give it everything you've got, you'll be fine. But stop training once and you will lose everything. Forever.

This is partly true. Scientific research seems to suggest that we can maintain our gains without exercise for about two weeks before we start to lose them (1). You will get weaker and your muscles will shrink. Although it is possible to maintain good body development with relatively little effort, you will need at least some training to achieve this.

However, if you start training seriously again after a long break, you will find that you get back to your old shape much faster than it took you to get there in the first place. Like my friend, you can expect to get back to your old shape five to ten times faster.

If you've been through this before, then you know there's a lot of truth to this. If not, you may still be skeptical. However, the fact is that muscle memory is something we can all benefit from as it is a fundamental part of our physiology. But how exactly does it work?

The science behind muscle memory

Cellular memory is a well-established phenomenon within the body. Ultimately, this is the process that makes us immune to many viruses we have suffered from in the past. The body generates and stores memory cells that are inactive for years and then come to life when we are attacked by the same virus years later to quickly destroy that virus.

Let's move on to the muscles.

The typical cell in your body has a nucleus, also known as the control center of the cell. However, muscle cells are slightly different in that they are larger, longer and tubular. These cells have many nuclei, each of which is responsible for a specific area of the cell (3).

Each nucleus has a limit to the size of the area it can control. In other words, once a muscle gets big enough, the existing nuclei will reach their limit in terms of the area they control and you will no longer be able to grow the muscle any further.

Visualize each nucleus as a guardian. If you hire a dozen guards to guard a building, then everything is fine. However, if you instruct that dozen guards to patrol the entire neighborhood, then it will be impossible for them to monitor the entire area.

The solution? We hire more guards. In the case of our muscles, the body adds new nuclei to the muscle cells. However, the muscles cannot make these nuclei themselves - they have to be added from satellite cells (4). These are the cells that lie dormant around the muscle cells and are occasionally called upon to repair muscle tissue and build new muscle tissue.

When needed, these satellite cells fuse with muscle cells and donate their nuclei to them (5). The ever-growing arsenal of nuclei within muscle cells allows us to continue building new muscle for years to come.

But here's the interesting part:

As soon as you stop exercising, your muscles begin to shrink - the technical term for this is atrophy - but the nuclei once accumulated remain (5). As soon as you start exercising again, your muscles will therefore grow back to their previous size at a much faster rate.

In one study, subjects trained for 7 weeks, then took a 7-week break from training and then trained again for 7 weeks (6). The scientists found that the changes in DNA levels brought about by the training were maintained during the non-training phase. This means that the muscle-building potential was fixed in the DNA for later use.

Another paper also concluded that muscle memory is a real phenomenon (7).

So what does all this mean? Well, if you've built up a significant amount of muscle mass (at least 5 to 10 kilos above baseline), then you're likely to have a lot more nuclei in your muscle cells than you did before you started training.

Even if you take a break from training and lose some muscle mass and strength, you will be able to rebuild this quickly. It is not necessary for new satellite cells to donate their nuclei to your muscles in order to grow them back to their original size. Instead, your muscle cells will use the previous starting point to restore their original size, which is much more efficient.

How long does muscle memory last?

It's clear that muscle memory is real and that it works amazingly well for bodybuilders. The question now is how long muscle memory lasts.

The scientists who wrote the paper we looked at above couldn't give a definitive answer to this question, but said that it lasts for at least seven weeks (6). This was the length of the non-training phase during their study.

Some hypertrophy experts suggest that these changes could last for many years and will lead to a rapid rebuilding of muscle mass even after a very long break from training.

In one study, scientists found that myonuclei are stable for at least 15 years and may even be permanent in nature (8). The authors of the paper also made the following statement:

"Myonuclei are harder to recruit in older people, however, and if long-lasting muscle memory also exists in humans, then early strength training could be considered a public health recommendation."

So it's better to start training early when muscle growth is faster. This will help you build muscle mass much faster and easier than with age.

It's not uncommon for people who train with weights in high school or college to stop training for a few decades, then start training again and make amazing progress over several months. With the research we have so far, combined with anecdotal evidence, we can assume that muscle memory lasts a lifetime.

The problem is that it is very difficult to conduct studies to determine the duration of muscle memory. This would require finding many subjects who were active and muscular in their teens and twenties, then stopped exercising and lost their muscles, and are now in their fifties, sixties or even seventies.

These subjects would also need to be willing to resume their regular training, be healthy enough to train efficiently and tell the truth about the gains they made decades ago.

Can this be done? My guess is yes. But even if we don't get the answer in the near future (or maybe never), we can still assume that muscle memory lasts a lifetime and we can use it to our benefit.

Does muscle memory help you build muscle faster?

People who have just started training build muscle at a much faster rate because their bodies are not used to the stress of training. This phenomenon is known as "beginner gains" and lasts for about three to nine months. Thanks to this sensitivity to training stress, the body ramps up many muscle-building processes, which includes an infusion of myonuclei into the muscle cells on a large scale.

During this time, you can expect to build muscle and get stronger every week. Once you get past the beginner gains phase and continue to build more muscle, it becomes much more challenging to continue making progress.

Building new muscle will become difficult, the process of adding more nuclei to your muscle cells will slow down considerably and your training sessions will have to become harder and more demanding to produce results.

This is the effect of repetitive effort in action (9). In other words, what has gotten you this far will not get you where you want to go. The more you expose your body to demanding training, the more resilient it will become and the less it will feel compelled to continue to adapt and improve.

Several processes are responsible for muscle growth, but the activation of satellite cells is the most important of these. And the whole thing gets even more complicated:

  • There are fewer infusions of satellite cells.
  • Your workouts need to get progressively harder to cause enough of a disruption to get satellite cells to donate their nuclei.
  • The disruption of homeostasis that occurs results in significantly less satellite cell activation.

Some people believe that we can use this whole thing to our advantage and accelerate muscle growth. As we have seen above, you lose muscle mass when you stop exercising, but the accumulated muscle cell nuclei remain (probably for life).

If we don't lose our hard-earned nuclei, the question is whether there is a way to resensitize the satellite cells to the disturbances of training and thereby speed up the process of merging satellite cells with muscle cells. And even if this were possible, the question is whether this would help us build more muscle or increase our overall capacity for muscle growth.

This is quite an interesting question and there are a few studies that have looked at this idea in more detail, although the scientists did not look at the influence of satellite cell activity.

In one study, 15 untrained men were divided into two groups (10). One group trained continuously for 15 weeks and the other group trained for 6 weeks, then took a break for three weeks and then trained for a further 6 weeks.

After the 15 weeks, the scientists compared the results of the two groups. No significant differences were found. In addition, the scientists did not observe any significant decrease in strength or muscle size in the second group after the three-week training break.

Another study came to similar conclusions (11). In this study, fourteen young, untrained men were divided into two groups:

  • Group 1 trained continuously for 24 weeks.
  • Group 2 repeated a cycle of six weeks of training followed by 3 non-training weeks a total of three times.

The training protocol for both groups consisted of bench presses three times a week at 75% of the maximum weight for one repetition for three sets of 10 repetitions. After the first six weeks, both groups had built up similar amounts of strength and muscle mass, which was to be expected.

Group 1 showed a gradual slowdown in progress after the first six weeks, while Group 2 made significantly better progress during their training weeks. Ultimately, the results slowed for both groups and both groups built similar amounts of strength and muscle mass within 24 weeks.

Oddly enough, both groups made similar gains even though one of the groups had not exercised for six weeks. Here are some possible reasons for this:

  1. All of the subjects in both studies were novice exercisers, which means they were extremely sensitive to training. If the researchers had used more experienced exercisers, the results could have been different. We could also argue that beginners are more resistant to losing their initial progress than more experienced exercisers. This would explain why they had not lost much of their progress after three weeks off training.
  2. Both studies included only a relatively small group of subjects. With more subjects, the differences between the groups could have been more significant.
  3. It is possible that the subjects who took the training breaks felt more motivated and enthusiastic and therefore put more effort into their training. Knowing that you only have a few weeks of training left before you get a break can be a powerful motivator to push yourself harder.

Additionally, these studies were relatively short-lived, so we shouldn't overstate the results. Sure, both groups were able to achieve similar results over a 15 or 24 week period, but how would these results change if the subjects were able to gain more training experience for one, two or three years?

Can we realistically expect to train 25 to 30% less and still make the same progress in the long run, all other factors being equal?

Finally, the periodized training groups did not build more muscle. If anything, they only achieved the results of the continuous training groups.

It's common sense that if you want to get better results from something, you need to put in more effort, not less. In the case of training, volume and intensity are crucial factors for muscle growth. Not training doesn't seem to be the best strategy if your goal is to achieve better results.

Of course, the importance of taking a break from training is unquestionable. We need periods of less demanding training sessions to regenerate, get a mental break and get back to training with more energy and enthusiasm.

What is the conclusion and what does this mean in practice?

The findings on muscle memory tell us that we can stop training for weeks, months or even years without worrying about losing our progress forever. The nuclei accumulated through resistance training are likely to last a lifetime and serve as a reset point for our muscle development.

In other words, the progress we have made once will come much more easily the second time around. We have upgraded our muscle-building ability for the foreseeable future - and perhaps for life.

If you get injured or ill and can't or shouldn't train, then you can be sure that you can get back to your old form much faster. You don't have to train through the pain to maintain your muscles. Give yourself time to heal completely and then start training again.

Scientific research also shows us that we are more resistant to losing our gains than we might have thought. Up to two weeks without training will not result in a loss of strength or muscle. So you don't have to worry about losing it all again after months of hard training if you take a week or two off.

The only disappointing thing is that we can't use muscle memory to build new muscle faster. Or maybe there's a way that science hasn't discovered yet.

In the end, maybe bodybuilding isn't such a thankless sport after all.




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