Oxygen consumption of muscle The cells of all the tissues of the higher animals use oxygen continuously, when it is available, throughout their living existence. When a tissue, such as muscle, is thrown into activity its oxygen requirement and oxygen consumption rise, but there is an appreciable oxygen consumption even during states of complete rest. The fact that most tissues, muscles not excepted, can endure complete oxygen deprivation for variable periods of time and can again resume their normal respiratory processes upon the return of its normal oxygen supply, has led to many misunderstandings and wrong conceptions regarding the method by which tissues use oxygen. Even in the absence of oxygen, carbon dioxide may be and usually is given off in appreciable amounts. This suggested to the earlier workers that the tissue was obtaining oxygen from some other source than atmospheric oxygen, that is, from some chemical combination. Muscles do have a strong affinity for oxygen and can remove it from chemical combination. This may be demonstrated by the fact that if a solution of alizarin-blue is injected into an animal, it can be shown upon killing the animal that the blood is blue while the muscles have their normal red color. Alizarin-blue solutions depend upon the presence of oxygen for their blue color. When reduced they are colorless. If now the animal's muscles are exposed to the air they will take on a blue color. The alizarin-blue has then not only reached the blood but the tissues also. The muscles have utilized the combined oxygen, thus decolorizing it, but immediately upon coming in contact with the air the lost oxygen is regained and the alizarin compound turns blue. This experiment, however, goes no further than to tell us that muscle has a remarkable affinity for oxygen and is capable of removing it, at times, from chemical combination. It tells us nothing about the normal mechanism of oxygen consumption. After periods of complete oxygen deprivation, an oxygen-consumption rate is found which is greater than normal or of that during the period immediately preceding the asphyxiation. This excess oxygen consumption during recovery is equal to that which was omitted during the period of asphyxiation. Earlier physiologists believed the tissues to contain a store of intramolecular oxygen from which they could extract their needed supply during periods of want, and replenish this store in times of oxygen excess. Later discoveries have rendered such a mechanism unnecessary and have given us a simpler and more natural explanation of the facts. When the acid was once formed, its removal was assured if the tissues were placed in an atmosphere of oxygen. Since the lactic acid reacted with the carbonates of the tissues, carbon dioxide was produced and accounted for its formation during asphyxiation. These observations show that oxygen consumption is not necessary for the immediate activity of muscles, but for the removal of the lactic acid formed anaerobically so that activity may continue. In the absence of the oxidative phase, the acid accumulates in the muscle and stops the working of the muscle machine, that is to say, fatigue occurs. It has since been shown that hand in hand with the removal of lactic acid in the oxidative phase there is an increase in the glycogen content of the muscles. In addition to that which may be formed by the muscles from the glucose coming to them in the blood, that an amount of glycogen equivalent to four-fifths of the lactic acid removed during the aerobic phase will be returned to the muscles. The remaining one-fifth of the lactic acid is oxidized with the liberation of energy, one portion of which is used to drive the resynthesis of the other four-fifths into glycogen and another portion is lost as heat.		Home Classes of levers Varieties of muscle Smooth muscle The blood supply to muscles The neurone Cardiac muscle On the nomenclature of skeletal muscles The nerve supply to muscles Structure of a skeletal muscle Central nervous system The reflex arc and reflex action Physiologic properties of muscle Mechanical Changes The effects of temperature on muscular contraction Muscle glycogen, its source and fate The reaction of muscles Oxygen consumption of muscle Determination of the oxygen consumption of muscle The viscosity factor in muscle and muscle efficiency Significance of the recovery heat Production of Electricity Amsterdam Traveler Troy: Fact or Fiction