The amount of venous blood returned per unit time depends on the difference between peripheral and central venous pressure and venous resistance to blood flow. So all factors that can affect peripheral venous pressure, central venous pressure, and venous resistance can affect venous return blood volume. The main ones are: i. The average filling pressure of the body circulation. The higher the degree of blood filling in the vascular system, the more the amount of venous return blood will be. When the blood volume increases or volume vasoconstriction, the mean filling pressure of body circulation increases, and the venous return blood volume increases and vice versa. Second, the contraction force of the heart. The stronger the contractility of the heart, the more complete the ventricular emptying during blood uptake. During the cardiac output period, the intraventricular pressure is lower, and the pumping force of blood in the atria and large veins is greater, and the amount of blood returned to the heart will be greater. Third, the change of body position. When the body changes from lying position to standing position, the veins in the low hanging part of the body expand and the volume increases, so the return blood volume decreases. Fourth, the squeezing effect of skeletal muscle. In the muscle movement when the muscle contraction, can be within the muscle and the muscle between the vein squeeze, so that the venous blood flow is accelerated, while the venous valve so that the blood in the vein, can only flow in the direction of the heart, and can not backflow. Five, breathing exercise. When inhaling, the negative pressure of the chest cavity increases, and the large veins in the chest cavity and the right atrium expand more, which is conducive to the return flow of blood from the peripheral veins to the right atrium, and the opposite when exhaling.