dunno anything about band work, so i can't comment. however, strengthening your hamstrings is good for lower back problems. i've had some low back problems in the past (slight bulge in a disc) and in physical therapy we did a lot of hamstring related work.
start laying face down and lifting one leg up and the opposite arm and hold them there for 5 seconds. then switch. i remember that as one of the exercises we were doing.
another one you can do is to get down on all 4, then with your palms face down, slide your butt back as far as you can and lower it to the ground. hold this position for 15 seconds at a time. it's a long slow deep strech. those are 2 of the exercises i remember doing, i can't remember any of the others (it's been a year). within a couple of weeks, my lower back pains were starting to go away. i was told to do these a minimum of 2x a day, 3 or 4x if possible, but it wasn't for me during the week.
so there's 2 things i remember that helped my lower back. strong hamstrings are important for the lower back, and the first exercise will help to strengthen them and strech them at the same time. strong abs are also essential, as they'll take the weight off of your lower back as well. dunno if these will help you or not, cause i don't know what your injury was, but they were helping me quite a bit. hope that helps!
Mike