|Soleus (49) lies under the flat gastrocnemius muscle in the calf. This is the only place in the body where a true vein is actually routed through a muscle. As a result, 49 is a powerful venous pump, responsible for pumping the blood in the veins of the calf back up to the heart.
When spasm blocks this action, constricted venous drainage can produce leg cramps. If the deep veins become too constricted, they must be bypassed. This overloads the superficial veins, causing varicose veins (abnormally swollen and twisted blood vessels).
Spasticity in 49 can also cause blood clotting in the calf. These clots are not usually a problem, unless they travel above the knee joint. When they do, they can cause stroke, heart attack, or pulmonary embolism.