Muscle memory, what is it and how does it work?

I've recently replied to some muscle memory questions. Ever wondered what this term means or how it works? Here you go...

All research and studies will have variable outcomes yet the most recent and agreeable reasoning behind "muscle memory" is as follows: 

Your body will come back to where you were much quicker than it took you to get you there referred to "muscle memory" (there are 2 types this and I.e. Remember how to ride a bike after years) 

It refers to memory of the brain on a movement of muscle not memory of or in an actual muscle!!

The nervous system mechanisms may explain the strength gains, but it doesn’t explain how you can gain back the muscle size so quickly. (Most people this the nervous system causes them to get the size gainz back quick-wrong, just strength) 

Unlike other cells, muscle cells have more than one nucleus (probably thousands). When your muscles get bigger, your body had to add more muscle nucleus. When you stop training the muscle has the same number of muscle nuclei. Meaning it is easy to build the muscle back to its previous size.