Figure 2

When the gastrocnemius and soleus muscles contract, they expel more than 60% of venous blood into the large popliteal vein (Figure 2). In the resting state, veins of the calf fill at 1 to 2 millimeters per second—actively by compression of the sole of the foot and passively during muscle relaxation. It takes 70 seconds to refill 90% of the blood volume back into the calf and 31 seconds to restore hydrostatic pressure. Basically, the calf pump efficiently contracts to return the venous blood from one segment of the extremity to another.

Figure 2. Deep veins of the extremity carry most of the return blood flow out of the leg. By anatomic situation, they are surrounded by muscle and fascia (fibrous tissue), particularly in those areas between the ankle and hip (e.g., foot, calf, and thigh). Blood that collects in these segments is compressed and expelled by muscle contraction; valves prevent reflux.  (From Gloviczki P, Yao, JST, eds. Handbook of Venous Disorders, 2nd ed. London: Arnold, 2001:18, Fig. 2.9.)

The thigh muscle is believed to contribute only a small portion of the venous return. In contrast to the 70-second refill of blood in the calf, the thigh requires less than 10 seconds to refill. Compression of the veins of the foot forces the blood out of the foot, and the blood is directed into the deep tibial veins. All leg pumps work together to move the blood from one segment of the leg to another for a venous return of blood to the heart.