Combating the sitting position, or the great slouching position, is a full time job - or at least it should be if you are interested in keeping your body strong and moving well. We spend a lot of time with our body in a compromised position (seated) and then we try to undo the damage with a couple hours in the gym. It's a noble effort but alas, one that will fail in the long run.
I, like many of you, spend a lot of time either in from of my computer or in my car. The combination of these two activities is a good part of my day even though I am fortunate enough to train clients and teach classes every day. Still, even for someone like me, I need to spend time each and every day working on thoracic mobility. If you've had neck or back injuries in the past (many) then you need to spend extra time to make sure you get things mobile and moving when you transition from inactivity (sitting) to activity (training).
Check out the following video for two really good methods to open up your thoracic spine and make you feel and move better!