I had lower back problems for many years and finally ended up having a spinal fusion. That was 42 years ago! And to this day if I don't walk at least a couple miles every other day, I start having some minor twinges in the back. I have always guessed that walking benefitted my back by strengthening the stomach muscles, but I am no whiz when it comes to muscles and anatomy. Also, I have to have a fairly stiff mattress or the sag in my spine when I lay on my side causes some minor back twinges that can occasionally blossom into sciatica.
Good luck - I hope you can fix your problem!
JEAN
2011 Specialized Ruby Elite - carbon fiber go-fast bike
DiamondBack Expert - steel road bike
Klein Pinnacle - classic no-suspension aluminum MTB