We are reminded that contracting the calves and moving the ankles every 40 or 50 minutes can prevent pulmonary embolism. Some users then asked how the calves could affect the lungs. Before introducing the principle, let me tell you a story. Around 1996, a 32-year-old female patient was admitted to the Kanagawa Kitasato University School of Medicine in Japan. The reason for her hospitalization was left-sided chest pain with dyspnea after activity, and it had been going on for ten years, during which her symptoms were getting worse. This patient’s job was making Japanese kimonos. She had been doing this work since she was 18 years old and sat on the floor approximately 12 hours a day. An initial chest x-ray showed significant dilatation of her pulmonary arteries, and further nuclear perfusion scans showed a lack of blood supply to multiple areas of her lungs, and a pulmonary angiogram showed multiple narrowing and obstruction of blood vessels. Based on this evidence, the physician diagnosed her with chronic pulmonary artery embolism. Because this patient did not have any other risk factors that could lead to pulmonary embolism, such as malignancy, pregnancy, obesity, and other congenital abnormalities in coagulation mechanisms, etc., the doctor determined that her pulmonary embolism was due to prolonged sitting, blood stasis in the lower extremities forming a blood clot, which dislodged into the pulmonary artery to form a pulmonary embolism. If this is a special case not representative, the 18-year-long observation of nearly 70,000 nurses at Massachusetts General Hospital in the United States is more convincing. While overall there was no statistical correlation between the occurrence of pulmonary embolism and the amount of time spent sitting per day, the least active 10,000 or so (sitting more than 41 hours per week outside of work) had more than twice the risk of pulmonary embolism compared to the most active 10,000 or so (sitting less than 10 hours per week outside of work). This trend was derived by excluding many other factors such as age, body mass index, caloric intake, smoking status, race, spousal education, menopause, use of anticoagulants, hypertension, coronary artery disease, rheumatic disease and dietary habits. Also, the least active people have a significantly higher incidence of coronary heart disease, hypertension and other diseases compared to the most active people. In addition to this, there is a lot of evidence that prolonged flight travel, long hours of computer work, and other jobs that require prolonged sitting are associated with the occurrence of pulmonary embolism. The root cause is the prolonged huddled position, which leads to slowed and stagnant blood flow to the lower extremities and the formation of deep vein thrombosis. The reason why deep vein thrombosis occurs mainly in the lower extremities when sitting is related to the characteristics of venous circulation: venous blood flow is different from arterial blood flow. Arterial blood flow relies on the contraction of the heart and the elastic retraction of the aorta, like a pump to the periphery; while venous blood mainly relies on the relative negative pressure generated when the heart is diastolic, slowly back to the flow, it does not have a strong driving force behind. In this way, it is natural that the blood coming close to the heart and high will flow back first, and the blood coming far from the heart and low will wait first. Once the heart has collected enough blood for the next contraction, it will immediately contract and pump it out, and the blood that waited for a while had to wait again. Waiting left and right is like a traffic light at an intersection. If the red light lasts too long, the next few intersections will not move. In this way, the stagnant blood in the veins of the lower extremities has a greater chance of coagulating and forming clots, and if these clots occasionally fall off in small pieces, they flow with the blood into the right atrium, through which they enter the right ventricle, which pushes the dislodged clots directly into the pulmonary artery. If the clot is small, only blocking small blood vessels may not have obvious symptoms, but once the accumulation of small becomes many, or a large clot, directly blocking the main trunk of the pulmonary artery, then it will produce obvious symptoms of dyspnea and chest pain. And this kind of difficulty in breathing through oxygen is not helpful at all, just like the root system is broken, and no amount of water will help. Without proper treatment, about one-third of the patients will die. Pulmonary embolism used to be considered a rare disease in our country, but over the years, more and more people are “sitting” and sitting for longer periods of time, and the number of cases is increasing, partly because of the increased attention to this disease. In the past, because of the lack of awareness, mistaken for myocardial infarction, was done coronary angiography is also a large number of people. Many people who play games all night in Internet cafes and stay awake for dozens of hours and eventually die suddenly must have some pulmonary embolism caused by deep vein thrombosis of the lower extremities. Pulmonary embolism caused by sedentary can be prevented by standing up, moving, and not being a lazy person. If it’s a long trip, remember to get off the bus after a while to rest, take a flight or a meeting to move your legs and feet after a while, and remember to drink more water to keep the venous blood flowing and smooth.