Metabolic equivalent

The Metabolic Equivalent of Task (MET), or simply metabolic equivalent, is a physiological measure expressing the energy cost of physical activities and is defined as the ratio of metabolic rate (and therefore the rate of energy consumption) during a specific physical activity to a reference metabolic rate, set by convention to 3.5 ml O₂·kg⁻¹·min⁻¹ or approximately:

${\displaystyle {\text{1 MET}}\ =1{\dfrac {\text{kcal}}{{\text{kg}}*{h}}}\ =4.184{\dfrac {\text{kJ}}{{\text{kg}}*{h}}}=1.162{\dfrac {\text{W}}{\text{kg}}}}$

Still another definition of 1 MET is 58.2 W/m² (18.4 Btu/h·ft²), which is equal to the rate of energy produced per unit surface area of an average person seated at rest. The surface area of an average person is 1.8 m² (19 ft²). Metabolic rate is usually expressed in terms of unit area of the total body surface (ANSI/ASHRAE Standard 55).

Originally, 1 MET was considered as the Resting Metabolic Rate (RMR) obtained during quiet sitting. MET values of activities range from 0.9 (sleeping) to 23 (running at 22.5 km/h or a 4:17 mile pace).

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