I have a pretty serious back injury (vaguely defined as spondylosis, which basically means "vertebrae in places they shouldn't be"). I started out with pilates-type PT, and worked my way to weight lifting. My current self-motivational exercise is deadlifting. It's one of those exercises where you can measure exact improvement, and I love it. It's not the only exercise I do, obviously! The most beneficial thing I do is actually rowing, followed by squats and kettlebell swings. But the deadlifting is how I motivate myself. I'm currently working on increasing my hand/wrist strength so I can lift more, as my hands are now the weakest link in my form.