Though this thread seems long neglected I could see no point in starting a new one. I've been lifting/bodybuilding for over forty years, basically since I blew my knee out in my twenties and had to give up boxing! Still work out most days and (not bragging, mind you...okay, maybe a little) still look better than most guys half my age. Although I dropped a lot of bulk as I got older.
Anyway, I actually got my start as a writer (one that made money!) turning out articles for fitness and bodybuilding magazines back in the 80s and 90s. Most of them defunct titles now, though I did get stuff published by MuscleMag International. I largely count that as my apprenticeship, learning how to write economically and to the point, before I turned to fiction. I occasionally think of pulling some of that old material together for a book but I have far more interesting projects to keep me from it.