I'm running into a bit of a hard time finding what the driving factor for newbie gains actually is. My google fu is only returning articles explaining at surface level what newbie gains are.
The basic consensus describes newbie gains as the phenomenon where new lifters gain muscle much faster than experienced lifters. I can't find what drives this though, and it doesn't mention the fact that many people experience newbie gains after years of improper diet once they actually go into a caloric surplus.
My basic assumption for newbie gains is simply that the further we are from our current hormone limits, the faster we will accumulate muscle tissue. On a very basic level, I believe our bodies just have excess building materials that it can comfortably dump into muscle mass. As we get closer to our limits our bodies become more conservative with those materials. This could also explain why fixing your diet/sleep habits can lead to newbie gains years after starting training. Both of those, when done properly, have been shown to increase testosterone and consequently free testosterone.
Does anyone know the true reason for newbie gains?
Edit: I suppose I should have been more clear, I am not asking about neuromuscular adaptation or the related strength gains. I am only asking about why muscles grow faster. There are several studies that indicate that protein synthesis is sped up. For example in this study, they took cross-sectional area measurements of muscle 4 times over the study. It showed that the newbies to training gained on average 3x more muscle tissue than those with previous experience lifting. Or this meta-analysis where it again showed that protein synthesis remained higher for several times longer in untrained subjects. I'm asking what the biological reason is for this, theories and articles are welcome.