I doubt the small to medium sized niche content will survive in real print form for much longer. And even then, the bodybuilding mags face a special challenge. With the bigger magazines and some smaller ones that skew toward the collectible hobbies, repackaging of old content has become a big thing. They reissue some stuff as ebooks, they offer pay access to their archives, etc..... Also a lot of money is still made from folks that just never bothered to stop their subscriptions, places like doctor's offices, etc.....
You just won't see that with bodybuilding magazines. It's a short attention span hobby meaning that a lot of the people involved are only in it for a few years, and many just aren't interested in the history of it, at least to the point of paying for it. So I doubt that you'll anyone offer archives of past issues, etc..... Also since it is a young men's hobby, piracy is pretty strong. The kids just aren't paying for them much in any form anymore.
It's been a while since I looked, but even the big ones were losing subscribers at a rate of #5000 - 10000 a year the past decade, and that just continues to grow.