The Superior vena-cava collects de-oxygenated blood to the heart aided by heart suction. This vein carries blood from left to right. Centrifugal force due to anticlockwise running helps this suction. If we run clockwise, the centrifugal force impedes suction. That is why, in olden days, health officers ensured that all carnival merry-go-rounds were run only in the anti-clockwise direction. As the heart is on the left side, for humans and animals, running anticlockwise makes the centrifugal force in the body to act from left to right. Whereas it is from right to left for clockwise running. Racing tracks, animal shows in circuses, bullock-drawn pelt on wheels, all mostly have only left turns. Stairways in temple towers have only left turns for going up. Clockwise running tires people.
Goteti Mvsr Krishna, Tadepalligudem, India