One thing that is slightly off topic but I will add anyway. I sit at a computer all day and have done so for years. At some point, my posture caused me to have problems with my upper back. It has given me trouble for years now. And when I run I feel like it causes my form to be a little stiff. Anyway, at one point I went to a physical therapist, and he had me do some exercises and they really helped. But then I stopped doing them and the pain came back. So now I'm going to start doing them again. The point is that I think upper-body strength training and maybe even stretching can help keep your form smooth and keep you from having such problems as I have had with my back. Since I have little kids, I may try using them as weights.
I have the same thing (sit at a computer all day). Sitting loads the back, and is pretty bad for it. Standing, kneeling, or squatting is much better for the lower back. I've found that getting up at work and walking around every half hour helps a lot. Also, I tend to find some excuse to run an errand, so I often get in a half mile to a mile walk during the day (I work downtown, so have places to walk to). And one of the things I look forward to every night is rolling out my back on a foam roller. I usually get some good cracks out of it, and then I just lay with the roller under my lower back for a few moments, which really stretches it out well. I do similar things on an exercise ball, and after all that stretching, plus some crunches and a yoga pose or two (namely, upward-facing dog), my back is usually feeling pretty good. This is all a time committment of about 5 minutes, which I can handle.
