FWIW, my lower back hurts when I'm not stretching my hamstring muscles. My orthopedist said that tight hams can really mess with your lower back. I have spinal stenosis, so I have to keep my lower back strong & happy. That means keeping my hams stretched & happy too. Guess it really is all connected.

At the risk of sounding like a broken record, I've really had many fewer aches & pains since I started Chi running. Previously, I didn't run because I always ended up hurting afterwords - knees, back, etc. I'm not perfect, but when I really concentrate on the form, it feels smoother and more fluid.