Oxygen saturation (medicine)
Oxygen saturation is the fraction of oxygen-saturated hemoglobin relative to total hemoglobin (unsaturated + saturated) in the blood. The human body requires and regulates a very precise and specific balance of oxygen in the blood. Normal blood oxygen levels in humans are considered 95–100 percent. If the level is below 90 percent, it is considered low resulting in hypoxemia. Blood oxygen levels below 80 percent may compromise organ function, such as the brain and heart, and should be promptly addressed. Continued low oxygen levels may lead to respiratory or cardiac arrest. Oxygen therapy may be used to assist in raising blood oxygen levels. Oxygenation occurs when oxygen molecules () enter the tissues of the body. For example, blood is oxygenated in the lungs, where oxygen molecules travel from the air and into the blood. Oxygenation is commonly used to refer to medical oxygen saturation.
Physiology of marathons
The primary components of an individual's VO are the properties of aerobic capacity that influence the fractional utilization (%VO) of this ability to take up and consume oxygen during exhaustive exercise. The transportation of large amounts of blood to and from the lungs to reach all bodily tissues is dependent on having a high cardiac output along with sufficient levels of total body hemoglobin. Hemoglobin is the oxygen carrying protein within blood cells that allows for the proper transportation of oxygen from the lungs to other bodily tissues via the circulatory system. In order for the transportation of oxygen in blood to be effective during a marathon, the distribution of blood needs to be equally efficient in order for a marathoner's oxygen demands to be met during a race. The mechanism that allows for this distribution of oxygen to the muscle cells is muscle blood flow. A 20 fold increase of local blood flow within skeletal muscle is necessary for endurance athletes, like marathon runners, to meet their muscles' oxygen demands at maximal exercise that are up to 50 times greater than at rest. Upon successful transportation and distribution of oxygen in the blood, the extraction and utilization of the blood within skeletal muscle are what give effect to a marathoner's increased aerobic capacity and the overall improvement of an individual's marathon performance. The extraction of oxygen from the blood is performed by myoglobin within the skeletal muscle cells that accept and store oxygen for utilization. These components of aerobic capacity help to define the maximal uptake and consumption of oxygen in bodily tissues during exhaustive exercise.