Computer Fitness

How do you keep fit and alert at the computer, sitting for hours a day can create many physical problems. I am a Triathlete in my spare time, this keeps me in good physical condition and I have set my workstation up to the best I can. Seat position, computer set to the correct height etc. What tips can you bring on board for a healthy life next to the computer?

I am a personal trainer and have been asked this before. Do pressups now and again that helps, do a couple of standing squats now and again. Go for a litle walk every 2 hours. Good to see you have your chair properly set up thats normally the main problem of many injuries