Which of the following conditions is NOT a known risk factor for pulmonary emboli?

The condition that is identified as not being a known risk factor for pulmonary emboli is regular physical activity. Regular physical activity actually helps to improve circulation and can significantly reduce the risk of developing blood clots, which are the primary cause of pulmonary emboli. Exercise encourages blood flow in the legs and throughout the body, which helps prevent the stagnant blood flow that can lead to clot formation.

In contrast, obesity, prolonged bed rest, and pregnancy are all considered significant risk factors for pulmonary emboli. Obesity increases the risk due to additional pressure on veins and potential complications related to blood flow. Prolonged bed rest can lead to immobility, which increases the risk of clot formation as blood pools in the lower extremities. Pregnancy poses risks due to increased levels of certain clotting factors in a woman's body, along with changes in blood flow and pressure in the pelvic area, which can contribute to the likelihood of developing clots.