How Veins Work - The Leg Pump
The leg pump relies on two factors to pump the blood back up from the foot and into the pelvis:
Movement
The movement of the muscles in the leg push on the veins and squash them. The most important of these movements is the calf muscle moving the ankle joint.
The picture on the left shows the calf muscle moving the ankle joint - watch how it squashes the vein within it when the muscle contracts.
Valves
Pressure from the muscles squashing the veins will make the blood move. But without valves the blood moves without direction and so the blood is not pumped out of the leg.
The picture on the left shows what would happen if there were no valves at all in veins but the muscle contracted as normal.
