IMO, trigger point work (self-applied and by massage therapist) is the way to go.
I have (had?) L4-L5/S1 bulges, and core work certainly helps, but my daily “stretching” sessions include hunting down and attacking trigger points, especially in QL, erector spinae/iliocostalis/iliopsoas (everything that originates on lumbar spine, essentially).
In terms of stretching, iliopsoas, rectus femoris and QL, it’s impossible to stretch them TOO much. Iliopsoas gets overworked by cycling and running, but is vulnerable for those of us with desk jobs–sitting is just plain bad.
While some back troubles are acute, most of us spend many years doing daily activities in ways that get us out of balance muscularly, and then when we add sports on top of that, everything that is wrong is brought to the fore. So if you want to stay active you have to just work harder to overcome whatever you’ve done to yourself for however long you’ve been alive.
PM with email address if you’d like my doctored stretching routine that apparently works well for people; one guy just emailed me that after a week he is doing much better.
When I was in teens through 20’s, I could easily crack/adjust my entire spine by myself, as I was really, really flexible and in good condition. As I grew older and less active for awhile, became progressively less flexible, and then I started running and stuff and guess what, the body didn’t like it so much. But after a good 1.5 years of concerted stretching and a commitment to twice weekly core sessions, I’ve recovered much of my back flexibility. This is not to say my back doesn’t tighten up a bit after a long or hard run–it does–but I can get back to my normal state in under 24 hours because I stretch daily. I haven’t been to a chiro in 2 years and have no plans to go back. IMO, a good sports massage therapist versed in trigger point therapy will do much more good.
Another thing that seems to be working is to breathe bilaterally for the bulk of my swim sessions. I know it’s making a difference, since I’m right-handed and a right-side breather, my right back was getting more of the workout. In just 4 months since I decided to go all bilateral, I’m noticing that my back is doing even better, and whereas I’ve been able to crack my back twisting only to the right, the left side is now coming around.
YMMV