Blog

When we train our muscles, they adapt in several ways. Our nervous system gets better at coordinating movements, and muscle fibers can grow larger. Muscle fibers also contain multiple nuclei, known as myonuclei, which help regulate the processes involved in maintaining and growing muscle tissue.

One particularly interesting idea is that some of the additional myonuclei acquired during muscle growth may remain even when the muscle gets smaller again. A study published in 2010 found that myonuclei gained during overload were retained during substantial muscle atrophy in an animal model. Further research in 2012 also observed that myonuclear numbers remained stable during periods of unloading and reloading.

That could help explain why a previously trained muscle has an advantage when training resumes. However, these findings don't prove that every human muscle permanently retains all of its additional nuclei or that myonuclei are the only reason muscle memory exists. Improvements in movement and coordination probably contribute too.

In practical terms, a break doesn't necessarily mean starting from zero. Once you begin training regularly again, some of your previous progress may return relatively quickly. How fast that happens depends on how long you've been away, your previous training, nutrition and other individual factors.

And that's a pretty encouraging thought for anyone who's had to stop training for a while.

Closing Words

A few weeks or even months away from training don't necessarily mean that all your previous work was for nothing. When you return, muscle memory can help you make progress again, even if it takes some time to reach your old level.

It also makes sense to adjust your diet and calorie intake when your activity level changes, while continuing to get enough protein. That can help you maintain as much muscle as possible during a break.