In Arnold's own book, "Education of a Bodybuilder," he states that he started when he was 16 years old and that one of his first training partners was a doctor. Looking at the pictures of him in the book going from that first year to the pictures of him at 19 alone tells you he was on something. The thing that made me angry later on was that he wrote the whole book to sound like it was only all his genetics and diet that made it possible for him to gain like that.