Find your primal posture and sit without back pain: Esther Gokhale at TEDxStanford

I haven't read all the other comments so not sure if this has been mentioned already. The modern concepts of posture may be wrong. I have a curved butt to shoulder area. It makes me look somewhat duck like. However, I never have any back aches etc. I know of people who are straight as a plank, and complain constantly of aches and pains. This TED talk will explain why curved is better than straight: [VIDEO]

I read about this a long time ago in a book by Esther gokhale called lose the back pain. I think she called it stack sitting iirc. There was another thing in the book that has really helped me over the years and it's called the shoulder roll. The way to do it is to roll your shoulders in counter clockwise motion and leave it when they move back. It really does help while sitting. That book was full of such things like hip hinging, walking properly, etc and pictures incidentally also of Indian men who do hard labor much like the loom guy in the article. Here is a relevant video from her: [VIDEO]

[VIDEO] I found this Ted talk helped me with some lower back and leg issues. I don't do exactly what she demonstrates in the video, but I find focusing on the 'tail out' posture helps a lot. Also regular breaks and going for walks.