Long Figure Study - Back Pose

Last semester I taught a long portrait and figure class at Watts Atelier. This is the demo that I did for my class. I finished the rest of it at home from a photo. I thought that doing a back pose, that this drawing would go by faster. Generally back poses tend to be faster drawings in my experience, you don't have to worry about a face. I was wrong though, I still ended up spending 40 + hours on this drawing! I am quite happy with the result. I was also trying to push  the 3 dimensionality of the figure without the use of a background, I think it worked out well.