I recently read McGill’s back performance book (which I manage to bring up in every other thread I post in). He said his research suggests that the keys to a pain and injury-free back are endurance of the core muscles and motor control, but strengthening the back simply for the sake of strengthening the back is not directly helpful.
His core group of exercises were the prone, supine, and side bridges, crunches for the abs, and the bird-dog exercise to teach spine stabilization. Also prime, prime emphasis on learning to lift with proper technique and to brace the spine in a neutral position while lifting.
An anecdotal comment on that- I’ve really never had problems with back pain or injury. I’ve tweaked it a few times but never anything that hurt for more than a few days… As far as strength goes, I deadlift and squat regularly, do GMs, RDLs, pull-throughs, etc, etc for accessory work, so I always felt my back was plenty STRONG. Well, when I started doing prone and side bridges, I could barely hold them at all- I mean I fell over after maybe 8 seconds of my first side-bridge… So you may be shocked once you try some specific exercises for core stabilization and see what you’ve been missing despite all the big lifts in the gym.
You might also look at Eric C. and Mike R.'s Neanderthal No More program, in case you have whole-body postural problems that are leading to the back strains. And their article on self myofascial release might help get rid of the tightness. I’ve been doing both for a while now and I’m liking it.