Leg Veins are faced with the difficult task of taking the blood up to the heart against the pulling force of gravity. To do this the leg veins depend on the contraction of the calf and thigh muscles to pump the blood. This is why walking is good for your circulation.
So when you walk, the contraction of your leg muscles pumps the blood up. However, as the saying goes “what goes up must come down” which is what happens to blood in the leg veins. Therefore, to prevent the blood from falling back down, nature has designed valves in the leg veins which open in only one direction: upwards. So the valves allow the blood to get through but when it comes back down, the valves shut and stop the blood going all the way down. The next contraction sends the blood even higher until it eventually reaches the heart.
In venous disease, the underlying problem appears to be damage to the valves. The abnormal reticular veins, for instance, act as “feeders” of the spider veins . The blood flow in these feeder veins can be compared to a “two-way” street. In other words, blood in the feeder veins can go back and forth. This backward flow through the incompetent valves dilates up the smaller veins (medically called “post-capillary venules”). These dilated post-capillary venules are commonly referred to as “spider veins”.
The same principle applies to varicose veins. The abnormal valve cannot stop the blood from rushing back down. The blood in these veins is oxygen low and in fact carries a lot of toxins. In the case of varicose veins, the increased pressure in the veins stimulates nerves in the vein wall, leading to aching, cramping and ‘heavy legs’ at the end of the day.