So how about blood pressure? When you get it checked, the doctor or nurse tends to ask you to rest your arm on the chair or table and to uncross your legs, putting your feet flat on the floor. The fear is that crossed legs might skew the reading by temporarily raising your blood pressure. By 2010, seven studies had indeed found that leg crossing does result in a higher blood pressure reading, while another study found it made no difference. However, many of these studies were small and relied on taking a blood pressure reading just once. One of the larger studies was conducted at a hypertension clinic in Istanbul. Researchers there took several readings with legs crossed and uncrossed. Again, blood pressure was higher when legs were crossed, but crucially when the measurements were repeated just three minutes after uncrossing the legs, blood pressure was back to the earlier levels. The greatest rise in blood pressure occurs in people already being treated for high blood pressure.

Two possible mechanisms have been proposed to explain why leg-crossing might lead to a temporary rise in blood pressure. One is that the action of putting one knee over the other sends blood from the legs up to the chest resulting in an increased quantity of blood being pumped out of the heart, raising blood pressure. An alternative explanation is that blood pressure rises because isometric exercise of the leg muscles (exercise without the joints moving) increases the resistance to the blood passing through the vessels. This might explain why crossing legs at the ankles doesn’t have the same effect.