If you’ve spoken to enough bro’s at the gym, I’m gonna bet you’ve heard one of them mention something about muscle memory at some point. Although it’s not quite what it sounds like, your muscles do have the ability to regain size and strength a lot faster the second (third, fourth.. etc.) time around. Your muscles don’t have a brain and they can’t recall ever being something, but with each time your muscles increase in size, they increase the number of nuclei they contain, thanks to something called satellite cells. These satellite cells are what allows muscles to be built in the first place (1) and make the process of regaining lost muscle that much easier and faster, giving your muscles a form of ‘memory’.

Satellite Cells

Muscle cells are unique in that, unlike most other cells of the body, they contain more than one nucleus. A nucleus is an organelle that contains the genetic material required to help grow muscle tissue and is what allows muscle protein synthesis (MPS) to occur – the process of turning the protein you consume into actual muscle tissue. Because muscles are extremely large – up to 5 times larger than other types of cells (2) – they require a greater number of nuclei to help drive enough MPS to sustain the volume of the tissue they support. Consequently, a single nucleus cannot synthesise enough protein to adequate hypertrophy the muscle. So what do muscles cells do? They call on their mates – satellite cells –  to come join the party and help out.

Satellite cells are cells located outside of the muscle fiber that are donated to the muscle fiber. It has been shown in a study that muscles actually add more nuclei to the cell before they grow so that as the muscle gets larger, each nuclei looks after the same, if not less, amount of tissue (2). The great thing about muscle tissue is that when training stops and the muscle starts to decrease in size (AKA detraining), they do not lose the extra nuclei they gained. instead, the muscle reduces in size but now has a greater density of nuclei per muscle cell (2).

The Ability to Regain Muscle Faster

Someone who has once gained a lot of muscle but then stopped training still has more nuclei in each muscle cell compared to someone with a similar amount of muscle mass, but who has never trained. In fact, this is one way scientists could determine just how much size a person once had. As the person starts training again after a hiatus, their muscles can skip the step of having to add more nuclei to the muscle cell before it can grow and go straight to increasing MPS to actually build more muscle tissue (2). Therefore, even though two people may have the same amount of muscle, the one who has been a lot bigger at some point prior in their life has the potential to regain muscle at a faster rate than the person who has to build it for the first time (3)! This is where the term ‘muscle memory’ came from; it’s not that the muscles remember they were once big – they just now have the machinery pre-built to accelerate growth again.

The Ability to Regain Strength Faster

Strength is a skill and, therefore, not only relies on the size of a muscle but many other factors such as neural adaptations (increased muscle recruitment, improved neural firing rates, coordination of muscle activation, etc.) and a reduction in inhibitory mechanisms (from Golgi tendon organs) (4). Unlike building muscle size, when it comes to absolute strength (i.e., the greatest amount of force you can produce), you have to train heavy – there’s no other way around it. Unfortunately, this means that unless you’ve got heavy weight to throw around, you will progressively lose your maximum strength. However, the neural aspect of strength is quite fast to recover – it’s the loss in muscle size that helps facilitate greater strength that can take longer. Thankfully, as we just discussed, lost muscle mass is a lot faster recover due to muscle memory and so regaining your strength won’t take as long as building it in the first place.

Conclusion

If you’re forced to take time away from training, it’s not all bad news – you can regain your size and strength faster than what it took to gain it in the first place. Thanks to the fact muscles don’t lose the nuclei they gain during growth, muscles have a form of ‘memory’ that accelerates the regain of lost muscle. Although it’s tough to lose some of your heard-earned gains, it’s reassuring to know that it won’t take anywhere as much time in the gym to recoup them.

References

1. Egner, I. M., Bruusgaard, J. C., & Gundersen, K. (2016). Satellite cell depletion prevents fiber hypertrophy in skeletal muscle. Development, 143(16), 2898–2906. doi: 10.1242/dev.134411
2. Bruusgaard, J. C., Johansen, I. B., Egner, I. M., Rana, Z. A., & Gundersen, K. (2010). Myonuclei acquired by overload exercise precede hypertrophy and are not lost on detraining. Proceedings of the National Academy of Sciences, 107(34), 15111–15116. doi: 10.1073/pnas.0913935107
3. Staron, R. S., Leonardi, M. J., Karapondo, D. L., Malicky, E. S., Falkel, J. E., Hagerman, F. C., & Hikida, R. S. (1991). Strength and skeletal muscle adaptations in heavy-resistance-trained women after detraining and retraining. Journal of Applied Physiology, 70(2), 631–640. doi: 10.1152/jappl.1991.70.2.631
4. Haff, G., & Triplett, N. T. (2016). Essentials of strength training and conditioning. Champaign, IL: Human Kinetics.