(DISCLAIMER: I'm reporting a study and my own experience. I'm not a doctor, physical therapist, certified coach, or anything other than an amateur runner.)
I don't have major back trouble. Several times in my life, I've misused or overstressed muscles in my lower back and have been down for a day or two. And, I have a small twinge in my lower back from time to time. Over the last 6+ years of running, though, I have experienced that I have much less trouble with my back when I run than when I don't. In fact, in those 6+ years of running, I have not had a single incident of my back going out. I also know that my twinge is much less likely to appear on the days I run than on days I don't run. A lot of that is probably attributable to the fact that I'm many pounds lighter than in my pre-running days.
Runner's World's Peak Performance reported on a study that showed that running is an efficient exercise for backs. So, there is a study that corroborates my experience. It's good to know that I have been doing something good for my back as well as my heart, lungs, and waist.
Here's the link to the actual study report:
Trunk muscle activation during moderate- and high-... [Appl Physiol Nutr Metab. 2009] - PubMed result
All that being said, though, December has been a wash for me as far as running. I had some upper thigh issues around Thanksgiving and took 8 days off. Then, when I ran again, I was extra sore. Add in the rains, a trip to the US, vacation here, and now a cold -- I could count on one hand the number of runs I've had in this month. That will change -- not only do I like to run but I like to eat. :-D
Run well, y'all,