Did you know that by engaging in physical activity and using the muscles in your legs you help your circulatory system move blood back to the heart? Consider the guards that stand in front of Buckingham Palace in London, England. They stand for hours at a time. To prevent blood from pooling in their feet, they must use their leg muscles to pump deoxygenated blood back to the heart to be reoxygenated. The unique structure of veins ensures that blood does not drain back to the feet because the veins have one-way valves at regular intervals that prevent the backflow of the blood once it has moved above a valve. So the next time you are in London, ask the guards if they are contracting their leg muscles to make sure blood gets back to the heart.
