The circulatory system returns blood back to the heart by means of both surface and deep veins. Because of the distance from the heart to the legs, blood pressure in those veins can be particularly low. The veins' one-way valves are designed to keep blood flowing in one direction, despite this low pressure. In fact, the leg's deep veins are responsible for carrying the majority of the blood back to the heart from the legs and are surrounded by muscle to aid in this task. During regular walking, the calves compress these veins and their muscles, helping propel blood against gravity. However, if such a vessel becomes distended due to inflammation, clotting, age, or undue strain, the vein's inner valve edges, or cusps, may not close completely. This lets blood flow backwards as well, creating a condition known as a varicose (VEH-rih-koas) vein. This can be both painful and unsightly. Since blood travels even more slowly through the nonmuscular surface veins, they may also become varicose, although this situation doesn't usually cause pain. To some extent, varicose veins may be hereditary and are often more problematic in women having successive pregnancies accompanied by edema. However, there are a number of preventive measures that may help avoid the development of these veins. Daily, brisk walking is generally the most beneficial, both for prevention and for comfort from pain and distension of existing varicose veins. Support hose can also help the legs maintain constant pressure against gravity, especially during long periods of standing. It may also help to elevate the legs several times a day, avoid extended periods of sitting, and to place the feet on some kind of support several inches off the ground while at a desk. Finally, drinking plenty of water throughout the day may alleviate some swelling and pain, preventing the fluid retention that often aggravates varicose veins. If you're concerned about your circulation or have questions about varicose veins, contact a healthcare provider.