A quick summary:
You hear people often referring to muscle memory - usually when they have been out of training for a few weeks and hope to regain muscle strength and size quickly. But do our muscles really have “memory" and how does it all work? Muscle memory literally is the quick regain of muscle strength and size following a period of no training or less training in muscles that were previously trained. When you start training, your muscle cells will steal nuclei from other cells to use as their own as this helps the muscle cells to grow. More nuclei present means more muscle growth (due to increasing protein synthesis).
It’s been shown that after training stops the number of muscle cell nuclei does not decrease, and can stay the same for 15 years. This does not mean that muscle strength and size stay the same. Just the cell nuclei adaptation remains the same for a long time while the muscle strength and size may decrease.
Therefore when it comes to training the muscles again they are ready to go and much more receptive to training than they may have been the first time around when they had to steal the nuclei from other cells.
It’s believed that this change in the muscle cells goes back to when we had to hunt for food in the summer then store it for the winter months. Moving very little in the colder winter months, the cells would remain adapted so that it would be easier to train them again (through hunting) when the summer came around to hunt again.
In conclusion, muscle “memory” is present. The increase in nuclei stored in the muscles from training help the muscles to regain strength and size quicker after longer periods of rest or no training.
