Describe the process for measuring oxygen uptake.

Measuring oxygen uptake (VO2) requires the measurement of the difference between the inspired and expired volumes of O2 over a given amount of time while performing the exercise. In general, the measurement time is usually one minute; that is, liters of oxygen per minute (L O2/min.). In the laboratory, the traditional method of measuring the amount of O2 used requires the collection of the volume of expired air in a Douglas bag at one-minute intervals.The bag's volume of expired air, percentage of O2, and percentage of CO2 are analyzed, and based on a number of valid assumptions involving the physical gas laws and the physiologic inert property of nitrogen at sea level, the metabolic use of O2 and CO2 production and the volumes of inspired and expired O2 also are calculated. Thus, the difference between the inspired oxygen volume (ViO2) and the expired oxygen volume (VeO2) is the oxygen uptake measured in L/min.