As you might imagine, LOTS of people want to get their product or service featured on these networks! QVC and HSN are looking to work with people who already have a name brand and a following. If you have self-published your book, you need to make sure it looks like a quality product and contains quality information that is uniquely your own. Once that's in place, you need to get the word out about you, the book, the special advice you offer (or your custom fitness solution). So before you can get them to consider you and your book, I'd advise that you hire a good PR firm to help market you as a fitness expert to a variety of media platforms (print, radio, cable, network TV). Forget gold--great editorial coverage is worth platinum! I'd also suggest you get some media coaching, so you can refine your message and pitch before you are put in the limelight. Once you get a buzz going for your book, your particular fitness approach, and a polished professional pitch, then you can reach out to QVC or HSN. On a side note: Books of this nature are often packaged with a video and maybe a branded exercise tool of some kind (rubber bands, inflatable ball, jump rope, etc.) In your industry a packaged product, versus just a book can be promoted for a higher price--something which would be more interesting to both QVC or HSN.
Best of luck with your venture!