VO2 is measured in which units?

VO2 is measured in which units?

• A. μmol/min
• B. L O2/min
• C. mL O2/hour
• D. mL O2/min

Answer: (D)

VO2 is the rate at which the body uses oxygen. Because it’s a flow of oxygen over time, the unit should express a volume of O2 per unit time. In physiology, the standard way to report this is milliliters of O2 per minute. This makes the value easy to relate to physiological rates, such as resting oxygen uptake (roughly a few hundred milliliters per minute) and peak exercise uptake (several liters per minute). You can also use per kilogram (ml/kg/min) for comparisons between individuals, but the fundamental measure remains milliliters per minute. Other options are less practical: micromoles per minute is a molar rate that would yield very small numbers and isn’t convenient for whole-body measurements; liters per minute is possible but less commonly used in standard practice; milliliters per hour would be too coarse to capture the rapid changes in oxygen uptake that occur during activity.

VO2 is the rate at which the body uses oxygen. Because it’s a flow of oxygen over time, the unit should express a volume of O2 per unit time. In physiology, the standard way to report this is milliliters of O2 per minute. This makes the value easy to relate to physiological rates, such as resting oxygen uptake (roughly a few hundred milliliters per minute) and peak exercise uptake (several liters per minute). You can also use per kilogram (ml/kg/min) for comparisons between individuals, but the fundamental measure remains milliliters per minute.

Other options are less practical: micromoles per minute is a molar rate that would yield very small numbers and isn’t convenient for whole-body measurements; liters per minute is possible but less commonly used in standard practice; milliliters per hour would be too coarse to capture the rapid changes in oxygen uptake that occur during activity.