The veins in our legs carry deoxygenated blood back to the heart. When we walk, the movement of our calf muscles helps the blood in our veins overcome gravity. But sitting down for a long time, especially with our legs crossed, interferes with circulation. This means that the deoxygenated blood in the veins flows more slowly, becomes thicker, and the blood platelets can stick together. Our veins become congested and our legs gradually become heavy and swollen. Anything that also slows down circulation and causes blood to flow less smoothly makes these symptoms worse. Not drinking enough water in the summer is an example. Air in planes or air-conditioned train compartments is often dryer than we think, and this means that we lose more water through the mucous membranes. The answer is as easy as it is effective: drink more. If you get thirsty while traveling during your vacation, you might fancy a beer or a spritzer, you are on vacation! But watch out. Drinking alcohol causes your body to excrete more water. So the outcome is counter-productive, and your circulation slows down even more. After a long trip, your legs can be so heavy and tired that they are visibly swollen.