As a preface, there are obviously several factors that go into such a consideration. Therefore simply assume that we are looking at a genetically average individual who has gone through puberty and is no longer growing, training and nutrition are being optimized for muscle growth.
Which then circles back to my question; What are realistic rates of muscle growth? Starting from the new lifter and ending at the advanced level. I would also prefer that FFMI be used as an objective measure of progress instead of subjective “beginner” and “advanced” labels, but if that’s not possible then so be it.
Please note that this question is not asking about general lean mass gains, but rather muscle mass specifically. It’s also not asking about individuals who are predisposed towards being notably different than average (such as those with short, tall, broad, or lithe frames) and is instead looking at the typical expectations from which deviations may be surmised. This question isn’t interested in rates of muscle regrowth, only new muscle. Finally, this question is not merely asking for the popular Lyle McDonald or Alan Aragon models of muscle growth.
I’m calling into question these models as being potentially inaccurate for the situation I’ve described above. After a lot of consideration, I’m really not sure what their measures are based upon, but they suggest that an average skinny guy in his mid 20’s could go from an FFMI of 18 to an FFMI of 23 in two years time. Having some more gym experience behind me as well as hearing the thoughts of experts and others leads me to believe that this is ridiculous.