The Skeletal Muscle Pump

The skeletal-muscle pump is the pumping effect of skeletal muscle on veins to increase blood flow. During exercise, muscles squeeze veins, effectively pumping blood back to the heart.

This is a significant factor affecting venous return which is the amount of blood that returns to the heart via the veins.

When the skeletal muscle surrounding a vein is relaxed, both the upper and lower vein valves are closed to prevent backflow of the blood inside the vein.

During activity, when the muscle on either side of the vein contracts, there is a squeezing of the vein, forcing blood both downwards and upwards. The lower valve of the vein is closed up and prevents backflow but the upper valve opens to allow blood flow up towards the heart.