It's not hard to find articles about the hazards of too much sitting. If you're stuck with a job that requires lots of it, that stinks. There are things you can do to mitigate it, but the best option is to do less of it.
If you do a lot of work on a computer, you might think sitting on a Swiss ball is a good ideal. Alas, not so much. A stand-up desk can be a great option, but they tend to be expensive. Fortunately, there are improvisational options. (Click on the images to see larger versions.)
At home, I use this improvised set-up for a PC with dual 27" monitors: 
And I recently built some platforms to use on an old computer desk with my 27" iMac:
(Unfortunately, using a plastic crate didn't work and the iMac took a tumble. It came up scratched, but otherwise in good working order.)
Not pictured is the stool for periodic high sitting; standing all the time isn't so good either.
Recently, at a hotel, the chair was broken so I needed to improvise something and wound up with this:
It worked great! I'll use it next time I'm there and really should have done this sooner. But better late than never.
So if you use a computer at work, see if you can convince your employer to get you a stand-up workstation. It's not just for the health of the employee (that's you)--and potential reduced health insurance costs--it may also increase productivity.
As mentioned, standing all the time isn't such a good idea. It can lead to back pain. But that's easily remedied by giving yourself the option to sit when you need a break. A leaning stool might be a good option--I've never tried one. But holy cats! This one is $500! Maybe I need to improvise one of these too.
At home, you should be able to improvise something workable for little or no money. And, as shown above, you might also improvise while on the road. Try it. Because sitting too much really is bad.
Be seeing you.
-gary