Don't improve your sitting posture: stand instead! We know about posture, but we're rubbish at it because humans are lazy! More scientists say you should stand or treadmill while working, and I definitely concur.

Standing is so much better for you: http://www.bbc.co.uk/news/education-20947605

and http://www.washingtonpost.com/wp-dyn/content/article/2010/10...

and http://www.nytimes.com/2012/12/02/business/stand-up-desks-ga...