hanzosword, I couldn't find the link in your profile, but are they your own original workout DVDs or do you mean you're offering a selection of them from other distributors/manufacturers?
Anyway, as I noted above in my first paragraph, one method I know that can really work is become an active participant in fitness forums, social media around it (Facebook discussion groups, Tweeting/re-Tweeting Twitter posts on the topic, etc.) - answer questions, chime in, become a fountain of knowledge. You don't have to pimp out your site in a tagline, but you could write something general (after a while, establishing yourself as not being there just to shill!) like "Fitness instruction, workout vid host" and people can click through more if interested. It can work where people respect your advice and see you're contributing and would like to own something from you. There's a theory too about "giving away" some of your work (like if you're a photographer) for free, or with a small watermark, in the idea it'll attract paying customers for gigs - sometimes you have to lose a little money to make money. So you could do Youtube excerpts or something, or supplemental updates, and keep the full-length ones steadily available.