"Gravity is constantly pulling on us every second of the day, and most of the day we are on our feet. The average person certainly does not have the occasion to have his feet above his head in the course of his usual daily life. The heart has to push blood quite forcefully to circulate it back up to the legs to the upper body. This, plus the force of gravity, plus the customary use of our legs, causes great pressure upon the walls of the blood vessels of the legs. In time, in a certain percentage of people, this pressure distends the walls of the veins, causing a painful and pathological condition which can eventually develop into varicose veins...yoga inversions have a positive effect on that condition."