I do 308lbs for 5x5 and that mobility/stretching aspect is really not to be underestimated. I do mobility/stretching every day and its great for your performance in the gym. On the other hand I immediately notice when I skip it for a while. Just experienced this last week, had been skacking on it for a couple weeks and my lower back was on some
shyt after my workout. Been totally back on my stretching/mobility routine the last few days and its back to normal/non flabby
So do mobility/stretching breh if you aint already doing it, regularly