Have you ever noticed your posture slowly change while sitting at a computer?
You begin with good intentions and maybe you have even adjusted the ergonomics of your
workstation. However long the fight for good posture might be, gravity wins everytime.
The average human head weighs about 10 -12 lbs, which is about the same weight as a bowling ball. Little wonder your head and neck hurt after hours of sitting slouched at a computer. Try holding a bowling ball in your hands, outstretched for even five minutes and your arms would be exhausted.
Let me offer a little advice, try taking breaks. Set time limits. Every hour stand up and do a few stretches or jumping jacks. These breaks if done well will not interfere with work but will be invigorating and refreshing and as a result will increase work productivity.
In the Sports Medicine world we also see that the things which "improve performance also help prevent injuries."