Although it's not an in-house activity, swimming (or other water exercises like the aquafit classes you see at YMCA's) is great exercise that's low-impact and easy on the joints and back. Pilates and yoga are also good and cheap (a mat, or the carpet, for a few bucks and you can easily find DVDs, usually quite cheap) if you're not concerned about cardio, and they may help with the back issues too (but common sense applies, DON'T continue doing a movement or such if you feel more than a "Ooh, I'm stiff/that's difficult" pain). Stationary bikes are also good, though if you don't already have one or one you can borrow, kind of expensive.
Facebook (Artist alley only)
Originally Posted by Moofingham
There's a vibe here that says "We're in this together!Through thick and thin fabric! Through cold water washes and burning hot irons! Though we might super glue ourselves to our projects, cut holes/gashes/oh-god-mom's-gonna-kill-me into the dining room table, we will stand strong together. Unless there is a 75% off sale at the Fabric store. Then you're on your own. And get the hell out of my way."<3