Your body requires oxygen to turn fat and sugar into energy, as well as to carry out many other biochemical reactions necessary for life. Oxygen is carried through your body by a protein in your blood called hemoglobin. In your lungs, oxygen binds tightly to hemoglobin, but in the rest of your body, hemoglobin loses its affinity for oxygen, releasing the bound oxygen into your body's tissues. The mathematical description of this process is called the oxygen-hemoglobin dissociation curve.
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Oxygen and Exercise
Oxygen is required to turn fats and sugars into energy. When sufficient oxygen is not available, lactate, an intermediate product in glycolysis, the metabolic conversion of sugar into energy, builds up in your muscles. In high levels, lactate can damage your muscle cells, contributing to pain, soreness and swelling after exercise. The need to make up the extra oxygen to clear lactate from your body, excess post-exercise oxygen consumption, is thought to partially underlie the increase in metabolism following exercise.
The hemoglobin protein resides within erythrocytes, red blood cells. Each hemoglobin molecule contains four atoms of iron that assist in binding oxygen. Hemoglobin binds oxygen as it flows through your lungs and allows oxygen to dissociate to feed your body tissues. If you do not have enough iron in your body, hemoglobin will not be able to sufficiently transport oxygen to your body, resulting in a medical condition called iron-deficiency anemia.
The Bohr Effect
The Bohr effect describes how the affinity of hemoglobin for oxygen changes depending on the local biochemical conditions. An increase in acidity, temperature and the concentration of intermediate chemicals in the conversion of sugar to energy—specifically 2,3-diphosphoglycerate—decreases hemoglobin's affinity for oxygen, causing oxygen to diffuse into the tissues. The local availability of oxygen also affects whether oxygen tends to bind or dissociate from hemoglobin.
Exercise causes an increase in acidity, temperature and metabolic intermediates and a decrease in oxygen in your muscle tissues. This causes an increased dissociation of oxygen from your blood flowing through your muscles, supplying them with much needed oxygen. Your body increases blood flow to your muscles to supply them with more oxygen. Warming up before exercise can help prime your muscles to receive ample oxygen by kick starting metabolism and increasing temperature.