I see the TS is banned, but I'll post this anyway.
I've started to go to the gym very regularly, and my lower back pain has reduced dramatically, to the point that I'm mostly hardly even aware of it. I do lower body work every other day I'm at the gym, including back squats, leg presses, etc. I also do ab work such as situps and use the weight machines which work the back. I also run at least a mile or two on the treadmill.
For the most part, I don't really hold back at all. Of course a little common sense is required. Such as, if during sit ups you really start to feel the pain in your back, it might be wise not to push yourself beyond your comfort zone so as to crank out those extra 5 reps. Needless to say, I've left the gym with a sore back numerous times, and one night recently I slept on the floor to get the extra support. However, it hasn't lasted more than a day, and was just sore muscles. Again though common sense is important. Try to know your limits, etc.