The CDC has issued warnings to those of us who sit for long periods of time. The concern started as travelers on airplanes were reporting more and more instances of deep vain thrombosis, blood clots that form in the legs. But these medical emergencies are not unique to travel.
Anytime we are sitting for extended periods of time our circulation to and from the heart is being restricted and pressure in these areas increases, putting us at risk for deep vain thrombosis. The highest threat is during eight hour periods of inactivity, similar to a workday at a desk where movement can be limited depending on an individuals habits.
CBS news provides this video on deep vein thrombosis:
So if you're stuck at a desk all day or doing a lot of extended travel remember you're at risk. Take breaks from time to time to get that blood pumping. Also, try to stretch your leg muscles as often as you can.