Discover the science behind muscle memory and why it helps you quickly regain strength and muscle after a break.
Think of the expression “muscle memory,” and there’s a good chance the phenomenon of never forgetting how to ride a bike instantly comes to mind. But there’s more to muscle memory than simply remembering how to perform a certain skill.
Muscle memory can also refer to the ability of previously trained muscles to build strength and size after an exercise hiatus much quicker than untrained muscles, according to research published in the Journal of Physiology. Of course, muscles don’t have legit memory like the brain does, so the term isn’t universally agreed upon within the research world. However, most experts say it does exist, says Brach Poston, Ph.D., an associate professor who teaches the neurophysiology of movement and strength courses at the University of Nevada, Las Vegas.
Based on the current research, there isn’t one clear-cut physiological mechanism, but scientists have a few theories as to why previously trained muscles can regain strength and volume fast after deloading, says Poston. Here are the three main hypotheses.
You’ve Established Motor Memory
When you repeatedly perform a new behavior — say, a kettlebell swing — a plethora of structural and functional changes occur throughout the central nervous system, research shows. Specifically, pathways between neurons (nerve cells that send messages throughout the body) are created, and connections between different areas of the brain are established, says Poston. As you practice, you also become more efficient at performing the behavior, so your swings progressively improve and you typically become stronger.
Even when you take a break from the behavior (e.g., you ditch kettlebell training to focus on other priorities), some of those connections remain. In turn, you’ll continue to cognitively understand how to do the skill, and when you pick up that activity again, you’re able to achieve a high level of performance faster than it took you the first time around, says Poston.
“It's like a path in the forest,” he explains. “When people are always going on it, it’s really clear. If they stop using that path, it starts to get [overgrown] a little bit, but that path is still there. [Motor memory] is kind of the same concept — it's been done before, so there are some lasting changes that are still sitting there under the surface that are ready [to be used].” Once you start kettlebell training again, you’ll be able to tap into those established connections and begin performing well — and building strength — fast.
You Have More Myonuclei
Myonuclei — the nuclei of muscle fibers — may also play a role. Outside of your muscle fibers are dormant satellite cells that, when you progressively strength train, bind to your muscle fibers and add extra nuclei, says Poston. This increase in myonuclei, combined with other mechanisms, leads to an increase in muscle size (aka hypertrophy), he says.
It’s thought that once you stop training, the domains of the nuclei (essentially their coverage area) added to the muscle will shrink, but the nuclei in their entirety won’t disappear for a long time, potentially years, says Poston.
When you start training again, you’ll already have more myonuclei than you did when you first began lifting. Plus, “since the domain has already been that [larger] size before and you already have the nuclei in place — it doesn't have to be added over time — [muscle size] increases faster than when you first did it,” says Poston.
Think of it this way: You start with 100 myonuclei in a muscle fiber, and you gain 10 during training. The size of their domain will shrink during a break, but you’ll still have 110 myonuclei in the muscle. Upon your return to lifting, “if you increase the size of some of them, the whole muscle size also is going to increase,” says Poston.
Your Previous Training Led to DNA Methylation
DNA methylation — a chemical modification of DNA that can be retained as cells divide and alter gene expression — may also be a contributing mechanism, says Poston. “Basically, DNA methylation means that when you train, the genes that regulate muscle size and are responsible for hypertrophy get upregulated,” he explains. “When you take off [with training again], those genes have already been activated, and so they get upregulated again easier. And that leads to an increase in muscle size faster than the first time you did it.”
For a better understanding of DNA methylation's role in muscle memory, imagine you had a factory that manufactured candles. If you halted production, you’d have machines, tools, and production lines waiting idly by, says Poston. Once you’re ready to pick up your candle business again, you wouldn’t need to repurchase all your equipment in order to create your product — it’s all right there, waiting to be “activated.” Consequently, you’re able to power up your business and churn out candles quicker than if you were starting from scratch.
The Bottom Line
While experts generally agree muscle memory is a real phenomenon, there’s no consensus on the mechanisms at hand and how great of a role they each play, says Poston. But don’t let that uncertainty stop you from harnessing its power: “If you're the average person in the gym training, you don't need to know the exact mechanisms — just know it happens, so use that as motivation to get in there,” he adds. “It'll be easier than it was the first time because you reached a certain level, so do it.”