The Respiratory-Circulatory Model: Concepts And Applications
Published 1984 · Medicine
It is generally known and accepted that activity of skeletal muscles in the limbs exerts a pumping effect on the veins and lymphatic vessels which pass through, or by, these muscles. The valves in these vessels, almost twice as many in the lymph vessels as in the veins, prevent back-flow through this pumping system. Therefore, the rate of flow of lymph and blood back toward the heart is in direct proportion to the amount of muscle activity, which generates a need for increased supplies of oxygen and blood-born nutrients, and for faster removal of carbon dioxide and catabolites [1–3]. This supply and demand equation is often out of balance: during exercise, demand may exceed supply. It follows, therefore, that during rest supply must, at times, exceed demand. Otherwise we would all prematurely experience organismic failure … death.