From Sanjeev Dua:

Re: Backache? Sitting upright could be culprit (Nov. 27, 2006): I read with interest, the recommendation for a 135 deg. Sitting posture. I assume that the stress comparison between the 90 deg. And 135 deg has been done with the back supported. Up to now the conventional teaching based on Axial Loading MR s and CT had shown an even distribution of weight across a normal disc in the 90 deg. Posture rather than in a slouch.

Sanjeev Dua
Consultant Neurosurgeon