The Weider Principles ring supreme.
Those principles were taken from what Joe learned from bodybuilders. He was quite honest about it in that he named them the "Weider Principles" but he learned them from bodybuilders.
For example, Mr. America 1945 Clarence Ross had big arms and Joe watched Clarence training a young man one day and Clarence was admonishing the kid for improper form on the barbell curl. The kid was humping the weight up instead of doing them in a strict manner as Clarence had shown him.
Later on Joe watched Clarence doing his own arm training and noticed that Ross was doing what he called "cheat curls". He asked him why and he said that it helped to do them some days to overload his biceps and aid growth and also helped him to be able to perform strict curls with more weight. Joe named this the "Cheat Principle".
Weider could be a real schmoe but he was also actually interested in what made champions, Champions.