When internet physiologists describe how you build muscle, the most common description is that intense physical activity creates microtears in the muscle and it repairs itself into denser and stronger fiber, a lot like scar tissue.
However, there have been plenty of studies that have shown you can build muscle without working out at all while on gear. So, that seems to suggest that there's another type of muscle building process going on while using peds. There's also the concept of "muscle memory". If you were in very good shape at one point, you have a leg up to get in good shape again quickly if you take a hiatus. Once again, this doesn't seem like a matter of breaking down muscle.
I've always thought the microtear thing sounded like bullshit, but assumed it was solid science. I've been thoroughly researching this matter (via a handful of half-assed google searches) and I'm actually not sure it is solid science. It seems like something people just keep repeating because someone said it at one point.
For those of you who follow studies (or are better at googling than I am), are microtears a dumber concept than deadlifts?