muscle memory

[jlp_2908]

Muscle memory is also a term used to regain lost muscle at an extreme rate due to atrophy. There are people who have gained like 20, 30, 40 even 50 pounds due to this "phenomenon"
It MAINLY has to do with the stretching of the fascia. There are other factors too such as neurological, # of muscle fibers etc. I dont think there ever has been a study on it but from personal experience and those of others it DOES exists.
Sorry I couldnt go in depth but Im sure you can find more information about it

To your original question, I think 10 years is much too long especially for only 20 pounds. The connective tissue binding your muscle fibers together would have shrunken back to their original state / adapted to the size of what they are currently