Dr. Phyllis Kozarsky of the Centers for Disease Control and Prevention in Atlanta said when a blood clot forms in an arm or leg, if a part of the clot breaks off and travels to the lungs, it could be fatal.
Kozarsky says people who have to sit for long periods can reduce the risk of deep vein thrombosis by doing a few simple things.
"Get up occasionally, and walk around. Exercise your calf muscles, and stretch your legs while you're sitting," Kozarsky said in a statement. "And select an aisle seat, when possible."
Travelers with higher risk of deep vein thrombosis should talk with their doctor about other preventive steps, such as wearing special stockings.