According to WebMD here are some stretches you can do at work. Working on a computer or at a desk can be strenuous on your body especially if you're in one position all day. Here are some tips to help you get through the work day.
Your hips and low back get tight from too much sitting. This seated stretch can open both.
Sit on the edge of your chair with your feet hip-width apart, directly under your knees.
Cross one ankle over the opposite knee.
Gently stretch forward.
This stretch will undo the chaos of your workday. Use it to calm your mind and open your low back after hours at the office.
Low Back Release
Shake (don’t stir) the tension from your low back with a twist -- all you need is a chair.
Turn sideways in a chair.
Hold the back of the chair with the arm closest to it.
Gently twist the front of your body toward the back of the chair.
Reach your other arm to the opposite knee or farther if you can manage it.