Muscle memory is a concept that suggests our muscles have the ability to return to, or close to, previous levels of size and strength faster than they originally adapted. Would someone who once exercised regularly really be able to regain their former levels of muscular fitness faster after being sedentary? Or do we start over from our original baseline?
Well I have good news for former exercisers who’ve taken time off. Your body actually does adapt faster. Here’s how!
Mechanism #1
Neuromuscular connections are relatively permanent. While they may need to be refreshed, they’re definitely not lost. Since exercises are skills, the faster you are able to properly perform exercises, the better you can recruit muscles and the faster you’ll adapt. Think of this as a road being built between two cities. City 1 is your brain and city 2 is your muscle. An individual who exercised in the past has already done all the excavating, prep work, and paved the road. The road may be in rough shape but repaving is a lot easier than having to construct the road from scratch.
Mechanism #2
New research has shown that there are actually structural changes within the muscles that allow muscles to regain strength and size faster when training resumes. Muscle cells have more than one nucleus (probably thousands). The nucleus of the cell is the command center and is in charge of creating more muscle. As muscle grows, so do the number of nuclei within the muscle. It was once believed that as the muscle shrinks the nuclei reduce in number. However, new imaging techniques have shown that this is not true. We actually hold onto these nuclei (for a LONG time, possibly permanently), and they increase our growth capacity and rate when training resumes. Think of these nuclei as construction cranes at the site for new high rise apartments. If you have more cranes, you can build more buildings (muscle) and build them faster.
Practical Relevance
• Get your kids exercising as soon as possible!! It’s easier to develop these nuclei when you are young. Since lean mass is such an important predictor of long term health, you would be doing them a HUGE favor.
• It’s not too late to start back up! Get off the couch and return to old form. Improving your level of fitness will give you the confidence to pick up sports you once played, which will further improve your fitness.
• Never exercised? While it’s easier for young kids to develop these nuclei, it doesn’t mean that you can’t build more when you are middle aged. In addition to the immediate benefits, you will also be investing in your long term health!
 Conclusion
Your body does make structural adaptations to exercise that allow you to return to previous levels of muscular fitness faster upon returning to training. While this is referred to as muscle memory, the term isn’t quite accurate. Muscle doesn’t remember like the brain remembers — it simply doesn’t lose some of the components that allow for growth.