Hmmmmmm.
Okay, here's how it works in a nutshell:
- You are born with skeletal muscle that grows as you age. This is where new cells are created, and this process ends around the cessation of puberty as growth hormone concentrations drop drastically, among other processes.
- When you train, these muscle fibers develop micro tears, that signal to the body that the body is under stress and these tears must be repaired. Not only do they need repair, but there is a need to make them either stronger, more dense, or develop a better efficiency. This is the big difference between set/rep ranges.
- The human body requires certain ingredients to help rebuild these muscle tears; one of which is protein, and the other main ingredient being nitrogen. AAS assists with both of these in that it increases the rate of both nitrogen retention, and the synthesis of protein into muscle fibers from diet.
- When you cease using the muscles, the body senses that the time of stress is over; and it will slowly catabolize the muscle, putting those nutrients to use elsewhere. This causes your muscles to shrink, and you do become weaker. This also can happen if the amount of muscle tissue existing requires values of protein/testosterone beyond that in which your body can produce naturally.
- Muscle memory is a misnomer. It should be really called muscle-brain connection as it's really just the fact that your synapses "remember" how to move the muscle effectively, which gives the illusion of added strength - until your body actually rebuilds the fibers.
- Permanent gains do not exist. You have to continually refresh the demands on the muscles and keep the required nutrients/hormones sustained to retain muscle. Otherwise, the body will deem it unnecessary, and remove it. This is easily the number one reason why so many state that natural gains should come before AAS, as a solid base will always be retained (with exercise) due to the fact it's what your body can support naturally.
Note: What you're referring to is indeed what HGH can provide, as HGH causes the generation of new satellite cells in muscle tissue.
I'm skipping some parts, but I just wanted to give a quick breakdown in between paper writing for this god-awful sociology course.
My .02c