I see this question popping up a lot.
From what I understand it stems from putting more muscle on than your genetic limit can handle.
I'm no expert, but I'll try to explain the best way I understand it.
We're all different (duh) so our genetics are going to play a huge roll in how we build and hold muscle.
So as healthy males we all make testosterone, the one thing that's really good at building and SUPPORTING muscle (hence why so many pros blast and cruise) so if you're a person with low test, and spend the next 3 months on 300mg building muscle, how much will your low test hold onto when it's all over? We can can make educated guesses from your blood work, but that's about it. Now if you are in healthy test ranges, a decent cycle and good pct should keep a good % of the muscle you built.
In other words, you need a certain amount of test to hold a certain amount of muscle "your genetic limit"
That's why every single person here will tell you to get your blood work done before hand.
If your natural test is in the toilet, it doesn't matter how well you cycle, pct, diet and sleep, eventually you will lose what that 300mg cycle gave you. But if you're on the normal range, you can do several cycles before you meet your genetic limit, if you're at the high end you can do even more.
That's why bloodwork beforehand is so important!
There's also ways to get around your genetic limit, but that's a big commitment.
If I'm wrong, or missing something feel free to tell me. Like I said, I'm no expert and only (trying to) explain how I understand it.
