You don't have to be a scientist to understand how blood and oxygen operate during exercise. Red blood cells, or erythrocytes, transport oxygen from the lungs to the rest of the body. Muscles and other cells in the body require oxygen to generate energy. During exercise, the demand for energy-making oxygen rises, so the lungs inhale more air and the red blood cells become saturated with oxygen.
Just like you use caffeine to get that "pick-me-up" in the morning, cells use oxygen as an ingredient to make energy. Little organelles called mitochondria use oxygen to transform sugar into fuel. The byproducts of this reaction include water and carbon dioxide, which are released through sweat and exhalation. As the intensity of a workout rises, the energy demands of the muscles rise and the oxygen consumption rate rises.
VO2 Max and Oxygen Debt
During an intense activity, the body eventually reaches its maximal oxygen consumption rate, or it's VO2 max. In layman's terms, your body is consuming as much oxygen as it possibly can. If you need more energy to continue working out and you've reached the VO2 max, then an "oxygen debt" occurs. When cells need energy and have insufficient oxygen access, they create energy anaerobically, or without oxygen. The process of creating energy anaerobically is expensive for cells. After your exercise, when oxygen is abundant again, these cells require extra oxygen to return to a normal resting state. In other words, red blood cells must pay off the "oxygen debt" incurred over the course of the activity.
Role of Red Blood Cells
Red blood cells transport gases, like oxygen and carbon dioxide, between the lungs and other cells in the body. Unlike most cells, these short-lived cells cannot reproduce themselves. Instead, bone marrow creates these cells through a process called erythropoesis. During exercise, hormones are released in response to low levels of oxygen. These hormones trigger erythropoesis in the bone marrow, creating an upsurge of red blood cells. More red blood cells means more oxygen carrying potential, which also means an increase in the VO2 max.
According to popular belief, athletes can develop so-called sports anemia, or low red blood cell counts. In reality, athletes have more plasma -- fluid -- in their blood, diluting the concentration of erythrocyte proteins like hemoglobin. Diluted blood gives a false illusion that there are fewer red blood cells in the blood. A more accurate problem that exercise causes is low iron, which will lead to regular anemia. Athletes can easily remedy iron-deficiency and anemia by taking iron supplements.
- Santa Barbara City College: Blood Cells
- Ohio University: Oxygen Consumption
- Nicholas Institute of Sports Medicine and Athletic Trauma: Sports Physiology: Maximum Oxygen Consumption Primer
- Biology-Online.org: Oxygen Debt
- National Institutes of Health: Sports Anemia, Iron Supplements, and Blood Doping
- Photo Credit Chad Baker/Photodisc/Getty Images