You’ve probably heard the term in a strength sports context: muscle memory. Muscle memory is what helps you regain your strength and muscle mass faster than when you first tried to grow them. The term suggests that your muscles would have memory. That is of course not true; your memory is in your brain and in that sense muscle memory is indeed a myth. But if we don’t interpret the term too literally, there is indeed such a thing as muscle memory, although that name is a bit unfortunate.

PROCEDURAL MEMORY

I don’t fear the man who practiced 10,000 kicks one time. I fear the man who has practiced one kick 10,000 times.

Was signed, Bruce Lee. And he had a point. If you do something often enough, at some point you will do it without consciously thinking about it. If you have practiced a kick 10,000 times, the 10,0001st kick will more or less come naturally. Just like entering your PIN or a known phone number. You’ve done that so many times, it’s become part of your so-called procedural memory, which is located in the cerebellum. The individual actions have become a fluid process – like calling up a phone number from your phone memory instead of entering the ten digits individually.

In short, your brain has become very good at quickly and efficiently ‘telling’ your muscles that they have to perform a certain (series of) action(s). So good, that the process takes place unconsciously, automatically if you like. The moment you start thinking about what you are doing again, a process that takes place elsewhere in the brain, things often go wrong. You often see this happen with darts players, for example, who miss singles at crucial moments, who they normally throw with their eyes closed. Apparently it is better to leave certain tasks to the unconscious.

The procedural memory is quite different from the so-called muscle memory, a metaphorical term usually used in the context of strength sports. Of course you’ll soon master a bench press again if you haven’t done it for years, but used to be weekly. But that is purely about the execution of the exercise and therefore concerns the procedural memory. By muscle memory, in strength sports or bodybuilding terms, we mean something else.

MUSCLE MEMORY

You are probably familiar with the phenomenon that after a (long) break a strength athlete needs less time to reach his old level than he needed to get there before. Some argue that the muscle must remember its old state and call this phenomenon ‘muscle memory’. It should be clear: a muscle does not ‘remember’ anything at all. All a muscle does is adapt to a certain load. If the load is heavier than the muscle is used to, it results in hypertrophy, or muscle growth. However, when the muscle is no longer stimulated, it decreases in size to its old size – this is called atrophy.

But how is it possible that when the muscle is stimulated again after a long time, it grows easier and faster than before? Let’s face it: the scholars are not yet in full agreement.

Some argue that this has to do with training sensitivity: after a long period of detraining, your body is more sensitive to training stimuli than if you have continued to train regularly. You react to your training like a newbie, and we know that novice strength athletes build muscle mass much faster than more advanced ones. That you ‘resensitise‘, perhaps already after 9-14 days of detraining, is considered plausible. The fact that you often experience enormous muscle soreness after you have not trained a muscle for a long time seems to be proof of this. Yet, strictly speaking, this is not what we mean by muscle memory. Muscle memory also seems to be in effect with ‘later’ gains, the muscle growth that you achieved when you were no longer a beginner and when, through adaptation, you were no longer so sensitive to training.

Muscle memory seems to have (mainly) to do with something in the muscles themselves, as research by Norwegian physiologist Gundersen from 2011 shows. Resistance training results in a permanent change in muscle tissue. Strength training creates new muscle cell nuclei because satellite cells, a type of stem cells, divide and develop into new muscle cell nuclei, something that ordinary muscle cell nuclei cannot do. This increased number of muscle cell nuclei is maintained, even if the training is discontinued (long-term). The increased protein synthesis due to the increased number of muscle cell nuclei could, in part, explain why someone who has trained a while ago becomes stronger and builds muscle mass relatively more easily than someone who has never trained.

Multiple studies seem to confirm that theory, but direct evidence for it has so far only come from animal studies, as shown by a 2020 meta-analysis from Maastricht University. Coach and author Greg Nuckols of Stronger by Science does not find the theory convincing yet and also notes that the increase in muscle cell nuclei as a result of strength training is not permanent. He does not doubt the existence of muscle memory in itself:

The question here isn’t, “is ‘muscle memory’ real,” but rather, “does this particular mechanism seem to be a primary driver of the ‘muscle memory’ phenomenon?

CONCLUSION

Yes, there is such a thing as muscle memory. If you’ve trained for a long time and then not for a longer period of time – months, or maybe even years – you will get to your old level much faster than the time it took you initially to reach that level.

However, much is still unclear about muscle memory: which mechanisms exactly underlie it, how long or short it lasts and what duration and intensity of training is needed to build muscle memory.