Pressure in the deep limb veins may be 90 mmHg or so, depending upon the length of the hydrostatic column from the heart to the foot. By taking steps and the contraction of the skeletal muscle surrounding the veins, venous pressure is sequentially decreased, to as little as 20-30 mmHg depending upon the walking speed. Pressure lowering requires the action of unidirectional valves in the veins. With cessation off walking, deep vein pressure gradually returns to its original value. The skeletal muscle pump is an important mechanism for assisting venous return to the heart.
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