I was at a couple of muscle type sites recently and the focus there seemed to be:

Join my site and: - see me work out nude, - see me pose nude & - discuss with the guys on the message board diet, training and stuff like that..

As for your site -- hmmm well I vote that its mainstream. I think the real test though would be if you also plan on getting any sponsors or affiliate merchants on your site -- what they think or how they classify it as.

Because, as I've found out with my dating tips site -- it doesn't really matter what I think -- a lot of affiliate merchants won't touch me.