As someone who's been here before (only mine was my mid-back), try finding yourself some Isometric Exercises. You want something that lets you work your muscles against the native weight of your own body and nothing more. When that starts to feel easy, you do the same set of exercises only with a 1lb, 2lb, then 5lb hand weight. Once you get to the point where the isometrics with a 5lb weight feel easy enough to do a couple reps, you should be able to go back to doing your normal free weights or nautilus strength training.