I have the bulging L5-S1 disk as does a significant fraction of the population over 40..
According to the Mayo Clinic,
url=http://www.mayoclinic.com/invoke.cfm?objectID=0000C8FB-D0CA-1B77-962480AEBC2F006D&page=1http://www.mayoclinic.com/invoke.cfm?objec...BC2F006D&page=1[/url]
"most adults - as many as eight or nine in 10 - experience low-back pain at some point. A herniated disk, however, doesn't always cause this pain. Disk herniation is often the result of a gradual, aging-related, degenerative process. These changes are part of the aging process and often occur without pain. Because of the natural course of disk degeneration, one-third of all adults age 20 and older show signs of disk abnormality. But only a small number of these people experience discomfort. The portion of the disk that herniates tends to shrink over time, and many cases show partial or complete shrinkage after six months to a year. About 90 percent of herniated lumbar disks get better without surgery."
I found all this was quite reassuring during my episode of severe back pain two years ago.. I could swim and bike without pain, in fact both of these actually helped the pain. Only running caused severe problems. My PT gave me a large range of exercises, and recommended both Pilates and yoga as maintenance in the long term. I had about four months off running, with weekly PT sessions and massage. I now have only mild pain, very little as long as I keep up with the core exercises and stretching.
Last year the back pain morphed into sciatica, which I'm still battling through. That too is responding slowly to a different set of core exercises and stretching. What really sucks is my limited training time now has to include a couple hours a week of core. I don't enjoy core exercises.
It's still the case that only running causes problems - no pain or issues at all when biking or swimming. I suspect this is just the basic overuse syndrome - whatever you did most of is what causes the problem. Ex-runners have problems from running, ex-bikers have problems from the bike..
Surgery is a last resort, and not always successful. My father-in-law had the surgery six months ago, but now is in as much pain as before.