Human exercise physiology

Abstract

The oxygen transport system in the human body is described from atmospheric air to working skeletal muscles. It is illustrated that the pulmonary diffusion capacity becomes critical during whole body exercise as the arterial oxygen tension decreases markedly. Furthermore, the Bohr effect on the oxyhaemoglobin dissociation curve means that, with a lowering of pH to below 7.0, arterial oxygen saturation may decrease to below 90%. In addition, the ability to increase cardiac output limits the oxygen transport capacity when working with several muscle groups at the same time, and muscle blood flow is reduced by approximately 30% compared with times when only a single muscle group is activated. Oxygen diffusion to the myocytes thereby becomes affected, while endurance training enhances blood volume and the number of capillaries surrounding the muscle cells as well as the size of the heart, and thus increases maximal oxygen uptake by approximately 50%.