MET

A MET, or metabolic equivalent of task, is a unit used to express the energy cost or intensity of a physical activity relative to a standardized resting value. One MET represents the conventional energy expenditure of sitting quietly at rest and is commonly equated with an oxygen consumption of about 3.5 milliliters of oxygen per kilogram of body mass per minute .^1,2

The MET value of an activity indicates how many times its estimated energy cost is relative to this standard resting value. For example, an activity assigned 4 METs has an estimated energy cost approximately four times the conventional resting value. METs allow activities with very different movements, such as walking, cycling, household work, or sport, to be compared on a common scale of absolute physical activity intensity .^1,2

MET values are also used to classify physical activity intensity. In adults, activity requiring about 1.5 to less than 3 METs is generally classified as light intensity, 3 to less than 6 METs as moderate intensity, and 6 METs or more as vigorous intensity. Compendia of physical activities assign MET values to hundreds of activities using measured or estimated energy expenditure .^1,2

A MET is a standardized reference rather than an exact measurement of an individual's metabolic rate. Actual resting energy expenditure and oxygen consumption vary among people and can differ substantially from the conventional 3.5 mL/kg/min value. For this reason, a given MET value represents a standardized absolute intensity but may correspond to different relative levels of effort in different people .^1,3