"The heart, an organ weighing about three hundred grams, is supposed to 'pump' some eight thousand liters of blood per day at rest and much more during activity

"The heart, an organ weighing about three hundred grams, is supposed to 'pump' some eight thousand liters of blood per day at rest and much more during activity, without fatigue. In terms of mechanical work this represents the lifting of approximately 100 pounds one mile high!" The amount of blood that descends to your legs is the same amount that the heart has to lift...