As a computer programmer, I sit in front of the computer for at least 7 hours each day.
This is the work I chose to do and I never get bored or tired of doing it even if it takes so many hours.
As you already should have guessed the problem of being sited for a long time is the lower back discomfort and pain you get after the first hour or so.
And it gets worst along the day.
In my case, my legs also become to feel numb after awhile.
When you are very concentrated on your computer work (may it be programming, writing an article using a word processor, doing account with a spreadsheet, and so on)  after awhile you feel something is not right with your body.
To compensate for this annoying sensation you unconsciously start to lean your torso forward and sometimes backward just to try to make the dumbness go away.
But it will not.
What I usually do and most people can't do because they are not allowed is to take a short 15 minutes walk around the block to give time for my leg and back muscles do some exercise so the blood can flow easily.
Now imagine that instead of sitting on a normal chair in front of a normal desk you could sit on a tall chair very much like a bar stool in front of a tall desk.
You keep working in a sited position just like you used to do.
Then, when you start getting those uncomfortable body signs we talked earlier, you simply step down of your tall stool or chair and keep working normally standing up on your feet allowing your lower body to have some space again.
You can even put one foot on the step of the chair for more comfort and lower back relaxation.
You can start to see this happen in lots and lots of places with amazing heath results for the people that, like me and you, have to work the long hours in the same sitting position.
If you miss the 15 minutes walk around the block don't make this suggestion to your boss.
On the other hand, if you want to produce more with your computer with this simple approach you can get one more working hour per single day.