Swollen Hands and Walking, on today's Moment of Science.
Do your hands swell up when you walk? If they do, it probably has to do with your circulation.
The circulatory system is a one way street. Blood flows away from the heart in the arteries, down the arms and legs then back up to the heart in the veins. When walking, our leg muscles squeeze blood back up though tiny valves in the veins. If you don't move your arms very much when you walk, blood pools in your hands and makes them swell. Plus, gravity acts on the blood and helps it stay down in the hands instead of flowing up to the heart.