I blew out my back last year running and I'm still working through it. None of this stuff should hurt your back, but we've had a couple of guys who described the same kinds of problems - mainly because of trying to pull too hard with the back when turning. It may help to concentrate on releasing the musculature and letting the turn come out naturally (you may also find that you can actually turn further that way).
I think I am one of those guys that Chris was talking about. I was so eager that I actually was in pain for a while. Difficult to describe but there is a difference between "relax" stretching and "muscle" stretching. From my own experience, if I have to use my muscle to force myself to do the exercise, something is wrong. However, if I relax my body to do the exercise, it is correct. Bottom line.....you should feel tired but no pain after the exercise. If you fell pain, you did something wrong somewhere. Hope that helped.