Whenever I used to play MOHAA or even just sit at the computer for a while, my back would start to hurt, so I looked around for a table or anything that would be more ergonomic and comfortable. I found something called the Comfort Slope, and since I've been sitting at it, I've realized it's helping my back pain. Check out this site and the literature, and you'll understand why it works so well!!
http://classicclassrooms.com/page80.htm