People love to tell you their stories about how quickly they came back after seemingly years of not training. They tell you how “muscle memory” worked in their favor and made it all so much easier than they expected. And you might ask yourself: Is there actually any truth to that? Does muscle have a memory of former glory days? Let’s delve into the science and find out.
First, the term “muscle memory” is a bit misleading because muscles don’t have their own brain with a memory. Instead, the term refers to how muscles can quickly return to their previous shape or “remember” their previous fitness level. However, science is still investigating the exact mechanisms of how this works.
There may be a significant neurological aspect to muscle memory, which places the “memory” within the brain rather than the muscle.
Other factors that could be responsible are at a cellular level in your muscle cell's nucleus.
There is also research into effects at the epigenetic level, i.e., the influence external factors can have on the expression of your muscle's genome.
Let’s dive deeper into these three different possible aspects of the “muscle memory” effect.
Muscle memory on a neurological level
One of the most important potential aspects of muscle memory has nothing to do with your muscles. It’s purely about the brain, or more precisely, the motor patterns your brain keeps saved even though you might not train for a while.
Any movement we perform is stored within the brain as a neurological pathway, which is like a movement program. This is true for all movements, from a simple Squat to a complex exercise such as a Kettlebell Snatch.
Any movement you repeatedly practice gets deeply ingrained into your brain as a neural pathway or movement pattern. Eventually, it becomes subconscious. One typical example of this is riding a bike: once you learn how to do it, you most likely will never forget it.
A lot of what we call strength is based on neuromuscular coordination, which is the efficiency with which your brain controls your muscles. When we do an exercise such as a Bench Press, we often assume it is simple (we just push the barbell up and let it come back down), but to move a weight is actually a highly complex process where our brain has to coordinate and fire a lot of neurological pathways.
While more coordinative tasks, such as juggling, probably come to mind when we talk about the neurological aspect of muscle memory, it is also essential for strength performance as well. Of course, muscle mass also plays a significant role (you can’t coordinate the strength of muscle mass you don’t have…).
When you take a longer break from training but resume it again later, your brain will likely find the motor patterns for your exercises again after a few tries. This allows you to find your way back to your old level (at least on the coordination level) much faster than if you were learning the movement or exercise for the first time.
Our brains are so powerful that this aspect of muscle memory is likely what you will feel the fastest because it is independent of the growth process that muscle cells go through.
The brain can quickly rewire your old motor patterns in as little as 1-2 weeks. However, rebuilding muscle mass is a process that may take longer.
Muscle memory on a cellular level
One of the reasons you can come back quicker from a long training break than someone who just started for the first time may lie deep within your muscles. Or, more precisely, the core or nucleus of the muscle cells. This aspect of muscle memory is tied the closest to the actual muscles you have.
When you stop training, the first visual loss of muscle is due to the loss of glycogen (carbohydrates stored within the muscle). When glycogen is lost, you also lose a lot of water content from the muscles, which makes them look smaller.
Next, the body begins to reduce the thickness of your muscle cells. However, the nuclei of these cells stay alive for quite a long time after you stop training.1 They just lose a lot of their cell mass.
When you start training again, your body doesn’t have to build new muscle cells. It simply rebuilds your muscle cells to their former volume. This is why getting back to your former muscle mass may take less effort once you start exercising regularly.
However, the amount of time you can take off training and still be able to keep your cell nuclei is likely not indefinite.
Epigenetic muscle memory
Your genetics play a huge role in your athletic potential. While they won’t stop you from becoming more muscular or defined, they do define your potential range, i.e., how far you can take your athletic development.
However, while your genes will not change, the expression of them can be altered. This process is called epigenetics, or the change in gene expression due to external environmental factors (in this case, exercise).
When you expose yourself to athletic training, a process called methylation occurs within your muscle cells. Here, a chemical tag called a methyl group is attached to the genome of your muscle cell.
This tag is passed along to future muscle cells as well. It essentially chronicles the training adaptations for future generations of your muscle cells.
Your former fitness, i.e., strength or endurance, is chronicled within your cells' epigenetic memory, ready to be reactivated once you consistently return to training. This aspect of the muscle memory effect could be more permanent compared to the neurological and cellular aspects.
This is another reason why, when you once were well trained, you may have an easier time finding your way back to your old form than someone who was never athletic.
If you find yourself in a situation where you return from a long training break (i.e., months), you can benefit from the muscle memory effect. To do so, try to recreate your old training habits.
However, ease back in slowly for the sake of injury prevention. Don’t try to do the same amount of repetitions or weights or run the same distances and times you once did. Start returning bit by bit and keep training consistently instead of rushing the process.
When will you reach your old form again? This is highly dependent on what your level was and how long you took off from training.
If you were training or performing at a high level and take a long break from training, you will likely lose your adaptations and performance. And the longer it will take to get back there.
However, a solid baseline of athletic fitness could be reached again within 4-6 weeks of consistent training.
Start by applying progressive overload, i.e., increase your training performance one step at a time, and allow your joints and tissues to readapt to your training load.
Thanks to the muscle memory effect, you’ll find it will not be as challenging as when you started training for the first time.
All in all, the “muscle memory” effect exists and is real. It’s just that the name is slightly misleading. In short, when we stop training, the initial losses we see in the mirror are not due to the loss of muscle cells but a loss of water within the muscle.
Later, the body will reduce the mass of your muscle. And eventually, the brain puts its memory of how certain exercises work into the back storage.
When you do come back to training, it can be a bit easier compared to when you first started training due to the three aspects of muscle memory:
Neurological: how your brain remembers old movement patterns
Cellular: the fact that your muscle cells' nuclei may still be there
Epigenetic: the way your gene expression is primed to bring back former adaptations
So forget the idea of forever losing your fitness. Breaks can be healthy, and your body knows how to pick things right back up thanks to muscle memory.