Here is some information that is not video, but with pictures. I can tell you that when I was having major back problems, picture number two method really helped me. That means I got a chair that would slant or used a slanted pillow. It really took the pressure off of my lower back and I could work with much less pain. http://www.wikihow.com/Sit-at-a-Computer
Since Doc is a Chiropractor she may have some better suggestions.