Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Here we are with another topic that is quite current in this time of returning from vacation and the very beginning of the new training season. We will talk about muscle memory and why returning to form after a break is much faster than when we first achieved that form.
What is muscle memory?
When muscle memory is mentioned in a conversation, it refers to one of two things. Most people think of the ability that allows us to automatically start performing some actions and movements without thinking about them. A great example is riding a bicycle. Once we learn to ride a bicycle, we no longer think about the details of that action, such as pedaling and keeping balance—it simply becomes normal for us. Also, we hardly forget those things, and we quickly remind ourselves if we get on a bicycle again after a long time.
This is what we will call motor learning in this article. It actually does not take place in the muscles, but in the brain—it is a neurological adaptation. For some time, it was thought that this was the only thing that existed, but it turned out that there is still some form of memory, i.e., “remembering,” in the muscles themselves.
We are interested in muscle memory, which lets us quickly regain lost mass after a training break. Let’s say someone trains regularly for a solid period, for example, a year. If a person takes a three-month break, they will lose most muscle mass gained the previous year. When they start training again, they will regain all the muscle mass much faster than they did the first time.
This is really well documented in the literature and is known from experience to a large part of exercisers. A very good example is now after the quarantine. For a lot of people, this was the biggest break they took from the gym for a very long period. Anyone who seriously took up training after the break saw how quickly muscle mass returns.
What is the explanation for this muscle memory, what is the mechanism?
As we said in the previous section, unlike motor learning, which takes place in the brain, some form of memory must also exist in the muscles themselves. Muscles must somehow “remember” their size, making it easier to return to that previous level.
Although the existence of muscle memory has been documented for decades, we only got the first major hypothesis regarding the mechanism in 2010, thanks to the work of Bruusgaard et al. Just briefly for easier understanding of the rest of the article, myonuclei are the nuclei of muscle cells. It was already known that when muscle mass increases, the number of myonuclei in the muscles also increases.
The accepted theory at that time was that if muscle mass decreased later, the number of myonuclei also decreased again. Bruusgaard and Gundersen hypothesized that the myonuclei number stays high even if muscle mass shrinks. They proposed this as a potential explanation for muscle memory.
This mechanism was the main explanation during the last decade, but it was questioned last year. The last year or two has seen fruitful research, resulting in many published papers. The main limitation of the earlier works we mentioned is that they were done on rodents, and these new studies done on humans did not replicate those results.
A new potential mechanism for muscle memory could be related to epigenetics. Seaborne and colleagues first showed in 2018 that changes in gene expression occur after weight training and muscle growth. These changes remain even when muscle mass returns to its original state after a break. They appear to help you regain your form faster when you start training again. More research on this topic is definitely needed, but the hypothesis has potential.
Conclusion
Although the exact mechanism behind muscle memory is still unknown, we definitely know that it exists. We can use this knowledge so that we do not have to be afraid to take a break from training, for whatever reason.
Lost progress returns fast with retraining, and a break can renew your desire to train.
