Sitting for a long time, calf stomach swelling is due to: lower extremity venous return need to overcome gravity, on the one hand, rely on the diastole of the heart to produce negative pressure, the lower extremity blood pumped to the heart, on the other hand the need for contraction of the lower extremity muscles (such as walking, running), to play a role in squeezing the muscles, increase venous pressure. In addition, the veins of the lower extremities have venous valves to avoid blood reflux. If you sit quietly for a long time, blood will accumulate in the lower limbs and there is no strong muscle contraction in the lower limbs, which is also the cause of swelling in the lower limbs. The symptoms can be relieved by adopting the lying position and elevating the lower limbs appropriately.