Holiday Travel: If you're sitting for 4+ hours, there is a risk of blood clots

Intro / Summary
It doesn't matter if you're riding on a plane, or you're traveling by train, or hitching a ride in the backseat. In all these holiday travel scenarios you're sitting and you're in one place for a while. Doctors say-- if you're in one of these seats for more than four hours at a time.... you're at risk for a blood clot.