I have the same symptoms as you; standing still, my lower back starts to ache after 30 minutes or so, but I can walk or run for miles and my back is fine.
My hamstrings are very tight from sitting all day, to the point that I cannot even bend 90 degrees at the waist with my back straight without discomfort in my hamstrings. I've assumed that tight hamstrings are the root cause to my back pain while standing, but I haven't fixed it yet.
The best results I've had in the past when I was more physically active were from doing "good-morning" exercises. I think it's because you build strength in the stretched position, which is important according to various books I've read like "relax into stretch" and articles on PNF stretching. When I was doing these exercises regularly I was able to put my forhead to my knees without doing any regular stretches.
My hamstrings are very tight from sitting all day, to the point that I cannot even bend 90 degrees at the waist with my back straight without discomfort in my hamstrings. I've assumed that tight hamstrings are the root cause to my back pain while standing, but I haven't fixed it yet.
The best results I've had in the past when I was more physically active were from doing "good-morning" exercises. I think it's because you build strength in the stretched position, which is important according to various books I've read like "relax into stretch" and articles on PNF stretching. When I was doing these exercises regularly I was able to put my forhead to my knees without doing any regular stretches.