Strengthen my back

I started a new exercise regime two weeks ago. It’s called Slim in 6. It’s from TV. Haha. Auuh, I didn’t order it, a friend did and I am borrowing it. Well, my back is getting stronger. And I guess I don’t know what I did, but over the course of the last year, I think my back has gotten stronger and my torso has shrunk a bit. It’s probably from yoga, (which I haven’t been doing lately), but will start again after my six weeks of toning and building strength. I am a bit worried about the program because most of the moves make my bad knee pop and crack so I really have to watch it. I am so ready to get Slim in 6 weeks though. You just have to work out six days a week for six weeks and you move to a more difficult workout every two weeks. The workouts are great for the strange climate changes we’ve been experiencing here in mpls. It has been really cold every other day so when I am working and begin to feel cold, I just get up and do the workout and it keeps me warm for a few hours. It’s gonna be all about getting my blood circulating this winter.

Does anybody know a great way to strengthen your back without needing some kind of elaborate home gym? It seems like the only time I can ever feel my back muscles working is during yoga, but I want more. Should I do push ups? I used a resistance strap attached to my door tonight and that seems like it has some back strengthening potential, but who knows? Give me some tips if you got ‘em!