What is a metabolic equivalent?

The metabolic equivalent of the task, known as MET or metabolic equivalent, is a concept frequently used to indicate the amount of oxygen or energy that the body uses during physical activity. A metabolic equivalent unit expresses the ratio of the average person's metabolic rate while performing some task compared to their resting metabolic rate. In practical application, METs is a way of comparing the level of effort and energy expended when people of different weights perform the same physical activity. The metabolic equivalent can also compare the aerobic intensity and energy expenditure of various physical activities when performed by a single person.

It is conventionally agreed that 1 MET is the equivalent of the energy or oxygen used by the body while at rest. One MET is considered the resting metabolic rate, or the metabolic rate at which the body consumes 3.5 milliliters of oxygen per kilogram of body weight per minute. In mathematical terms, 1 MET = 50 kcal/hour/m2 of body surface.

The harder a body works during a given activity, the more oxygen is consumed and the higher the corresponding MET level. Activity between 3 and 6 METs is considered moderate intensity, such as walking the dog. A person experiences an increase in breathing and heart rate and 3.5 to 7 calories are burned per minute. Vigorous activity, 6 METs or more, burns more than 7 calories per minute and includes running and playing basketball.

The MET concept can be used to make fitness recommendations, to plan or monitor physical activity, or to measure aerobic intensity levels. For example, it is recommended that people get between 500 and 1,000 MET minutes per week for good health. This equates to at least 150 minutes of moderate-intensity or 90 minutes of vigorous-intensity activity per week. The metabolic equivalent concept is also useful in prescribing exercise, such as determining the activity required for the rehabilitation of patients with various conditions.

METs are estimated predictions based on controlled experiments and are highly inaccurate when applied to specific individuals. The actual energy expenditure, often described as "calories burned," during a physical activity depends on a person's body mass, fitness level, and a variety of other circumstances. Published metabolic equivalent values ​​and MET-based exercise "calorie calculators" are averages only and should not be used by individuals. Measuring actual METs usually involves a treadmill test, in which a person wears a mask that measures oxygen consumption and carbon dioxide exhalation.

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