This puts you at risk for something most of us are unprepared for and could become deadly.
Lou Baxter explains in today's health news.
Frequent road trips home during college were a part of life for college student Mallory Click.
Mallory, "I was trying just to drive straight through, just so I wouldn't be wasting time driving."
However, the five and a half hour trips nearly took her life at age 21.
Mallory, "My leg was just throbbing and I had a hard time sleeping that night. I was just kind of tossing and turning all night."
The pain and swelling were caused by deep vein thrombosis, a blood clot in her leg that nearly doubled its size and sent her to the emergency room.
Mallory, "It's crazy. I would have never thought at such a young age I could get blood clots."
DVT impacts two million people a year in the U.S. and Dr. Heather Hall says most people know nothing about it or its risks.
Dr. Hall, "It's when that clot breaks off and travels to the lung and becomes a pulmonary embolism that it can be fatal."
Every year, DVT kills more than 100,000 Americans, more than breast cancer and AIDS combined.
Dr. Hall, "Anything that makes a person less active or less mobile is going to put them at risk for developing a DVT."
She says that if you are driving, then you should stop every four hours to stretch your legs to get your blood flowing.
Dr. Hall, "If you're stuck on a flight and you can't get up and walk, something you can do while you are sitting in your seat is calf raises. So, keep your toes on the floor and raise your heels up and down."
Plus, stay hydrated. Dr. Hall, "Try to avoid alcohol. Try to avoid becoming dehydrated when you fly."
Also, know your risk factors.
Dr. Hall, "Are you a smoker? Are you overweight? Do you have a family history of developing blood clots?"
These are all things Mallory is aware of now.
Birth control pills can also increase your risk of DVT. If you experience sudden pain and swelling in your calf or leg, Dr. Hall recommends that you see a doctor immediately.