The human body is about 60% water. Around 2/3 of body water is intracellular fluid, and 1/3 of body water is extracellular. If we remain standing or sitting for an extended period, the leg muscles remain stationary and blood circulation in the veins will slow down. The blood flowing to the legs will not flow smoothly back to the heart. This increased pressure on the blood vessels may lead to excessive accumulation of extracellular fluid between the cells, resulting in edema, or swelling, in the calves,ankles and/or feet. Apart from long-distance travel, edema can also be caused by other conditions such as chronic heart failure, kidney diseases, arthritis, and hypothyroidism.