Hi there,
I am and have been a fitness trainer for ten years, and have written gym instruction manuals that cover all sorts of topics, including not only actual strength training exercises, but also weight loss and aspects like diet. I've also written a number of books on general health and fitness besides, as well as on a number of other topics, so I'm an accomplished writer as well. I'm sending you a private message with some interesting material that I think should be included in a book of this sort - please note that this material is SUBJECT TO COPYRIGHT, from a previous book.
Please consult my private message, because I'll be putting in information about your book there that I can't put in a public bid.
I'm charging about $250 for about 20 pages - these are standard rates. If you wish more pages, the price will increase proportionately. I can also include diagrams and sketches for the exercises if necessary - the rate for diagrams is about $5 per sketch (these will usually be human-body sketches, so this is a good rate).