i dont know if there's any science behind it but i trained for years then stopped for about 4 years. This year when i started up i got really good gains early on but i dont know weather thats because of training well or muscle memory.

One example of the top of my head is dwain chambers. He got banned for steriod use and even now after x amount of years people stll say he should be banned as some people believe it to stay lurking in your muscles for years after then pop up again when training hard again. Perhaps this can generally be said for muscles in general but im not to sure myself