Leg veins and the muscle pump
The leg veins carry a large volume of blood, which collects in the lower legs as a result of gravity. These veins are surrounded by strong calf muscles, which act as a kind of pump to help the blood return to the heart. Every time you use your leg muscles, by walking or exercising your feet and legs, you are helping the 'muscle pump' to do its job.
When you sit or stand still, the muscle pump stops working and the action of gravity pools blood into the leg veins. Pressure begins to build up and fluid starts to leak out into the tissues, until the muscles get going again.
An active healthy muscle pump helps the legs stay feeling light and comfortable. Anything that interferes with this mechanism, including certain lifestyles, can lead to a build up of fluid and uncomfortable feelings such as aching, heavy and tired legs.
Excess fluid leaking out into the surrounding leg tissues leading to aching, heavy, tired legs.