Oxygen consumption is essential to sustain life. The ability to take in and utilize oxygen is necessary for optimal health. At rest everyone consumes 3.5 ml/kg/min. which is one metabolic equivalent to oxygen consumption or MET. METs are used to gauge the intensity of activities based on oxygen consumption. In the American College of Sports Medicine Guideline for Exercise Testing and Prescription, there is a table of activities from A to Z and a range or MET values associated with each activity. The MET level is multiplied by 3.5 to yield a volume of oxygen consumption (VO2) value expressed in milliliters of oxygen per kilogram of bodyweight per unit of time which is one minute. The product of the bodyweight in kilograms and the time engaged in the activity or exercise yields milliliters of oxygen consumed and utilized. The milliliters are divided by one thousand to give liters of oxygen consumed. The liters of oxygen are multiplied by five to calculate the calories burned for the exercise or activity. Metabolic equations to calculate VO2 are established for treadmills, cycles, arm ergometers, step tests, and rowers. The equations were developed by using a metabolic cart collecting expired gases.
At this point, it becomes important to understand that inhaling and exhaling at the lung is ventilation. Respiration refers to oxygen and gas exchange at the cellular level and the basis of metabolism. Analysis using a metabolic cart and collecting expired gases is generally only used in research settings. The collection of expired gases is used to determine what fuels are being utilized and exercise intensity. In this setting, the respiratory expiratory ratio often referred to as respiratory exchange ratio (RER) as well is very important. RER is the carbon dioxide to oxygen ratio of the expired gases. A RER of .7 is a lower intensity where fatty acids are the primary energy source. At an RER of .8 to .9, there is a combination of protein and carbohydrates utilized for energy. A RER of one or above means that carbohydrates are almost exclusively being used for energy. A RER of 1.1 demonstrates that a maximal test or intensity has been reached. Oxygen consumption values are critical to establish exercise intensity, fuels utilized, and caloric expenditure. For articles on nutrition and exercise, visit our blog at tpnperfectbodies.com.