Even if You Exercise Regularly, this One Habit Could Undo All Your Hard Work

Updated: Feb. 10, 2021

Exercise protects your heart, but not if you sit at a desk all day and binge-watch TV at night. Here's how to lower your risk of blood clots.

woman at gym on exercise machineGaudiLab /Shutterstock

If you work out on a regular basis, you know that exercise offers plenty of benefits other than weight loss. So you probably assume that with regular exercise, your circulation is in good shape. Not so fast.

“Working out is a good way to improve your circulation,” says Amy Mullins, MD, medical director for quality and science at the American Academy of Family Physicians. But it’s actually less about the exercise you do and more about how active you are in general. “You may be at risk for blood clots if you’re sedentary for much of the day. Regular movement is important for circulation and to prevent clots from forming.” 

Research shows that people who live a sedentary lifestyle, even if they meet exercise guidelines, have an elevated risk of blood clots in the legs—and those clots can have life-threatening consequences.

How blood clots develop

“The veins are bringing blood back to the heart after arteries have given oxygen and nutrients to the tissues,” says Mary Cushman, MD, a professor of medicine at the Larner College of Medicine at the University of Vermont. “It’s particularly difficult for the veins in the legs to do their job, because they have to bring the blood up against gravity.”

The body relies on leg muscles to push the blood back from the legs to the heart, she says. If the legs are immobile for hours at a time, the blood can begin to clot, leading to what’s known as venous thromboembolism (VTE). Though there are other risk factors for VTE—surgery, traumatic injury, cancer—simply sitting for extended periods can be a primary cause. (These are the silent signs of a blood clot you should never ignore.)

When a clot moves or a section breaks off, the results can be fatal. It can travel to the brain, causing a stroke. A clot also can lodge in the lungs, leading to a pulmonary embolism which can also be deadly. VTE affects between 300,000 and 600,000 people in the United States every year, making it the third leading vascular diagnosis after heart disease and strokes. Yet, according to Dr. Cushman, worldwide awareness is low.

Using TV as a barometer

To detect the impact of prolonged sitting, Dr. Cushman and a team of researchers tapped data from the Atherosclerosis Risk in Communities Study, which followed more than 15,000 people (ages 45 to 64) for 20 years. They looked at the incidence of VTE and how it related to the volunteers’ TV-watching behaviors. (TV habits are a good way for scientists to judge whether someone is living a sedentary lifestyle.)

Sure enough, the data—presented at the American Heart Association’s Scientific Sessions in 2017—showed that people who watch TV “very often” had 1.7 times the risk of suffering a life-threatening blood clot compared to people who seldom or never watched television. To the researchers’ surprise, they found that even frequent TV watchers who exercise regularly were still 1.8 times more likely to get a blood clot than exercisers who rarely watch television.

“You can be physically active and also have sedentary behavior,” says Dr. Cushman. “They aren’t just opposites. People who are physically active don’t necessarily have low sedentary time.” In other words, regular exercise is important for many health reasons, but it’s not enough in itself. People also need to remain active throughout the rest of the day (or throw on some compression socks when sitting idly).

Limit your sitting

Dr. Cushman advocates limiting the amount of time you spend sitting, which includes any prolonged periods such as working at a desk or taking a long flight. “Do your 30 minutes of moderate exercise every day,” she says, “And then if you want to sit and watch TV for three hours at night, you should be moving during part of that time at least.” Dr. Cushman walks on a treadmill while watching TV and sets an hourly alert on her watch to remind her to get up and move around regularly while she’s working.

She has two pieces of advice to help avoid the dangers of VTE: “Number one is to educate yourself about this disease,” she says. “When you are not aware, you can actually die because you don’t get treatment early enough.”

There are two types of VTE: deep vein thrombosis (DVT) and pulmonary embolism. Symptoms of DVT include pain or tenderness in your calf or thigh, leg swelling, redness, and skin that feels hot to the touch. A pulmonary embolism causes unexpected shortness of breath, rapid breathing, chest pain, increased heart rate, and light-headedness. This indicates the blood supply to the lungs has been cut off—which can be fatal. Recognizing the symptoms and seeking medical help right away could make all the difference to your chances of survival.

Know your risk

No two people are alike so it’s important to know your particular risk factors, says Dr. Mullins. “Everybody is unique and risk factors for blood clots can vary,” she says. “For example, having cancer, undergoing surgery, or being a smoker can increase your risk for a blood clot. Also, those who travel over four hours could be at risk. It is important to discuss your individual risk factors with your primary care clinician.”

Although VTE most commonly affects those over the age of 60, establishing good habits when you’re young will reduce your chances of developing chronic conditions like heart disease and strokes later in life.

Dr. Cushman’s second piece of advice: “Keep moving,” she says. “That involves not being sedentary, getting the recommended physical activity, and eating a healthy diet, which will help prevent this disease as well as almost every other chronic disease. These are the key things about preventing disease and maintaining a healthy long life.”