What are exercise Metabolic Equivalent of Task (MET) values?

From the Guidelines

MET values are a standardized measure of the energy cost of physical activities, ranging from sedentary behavior (1-1.5 METs) to vigorous activities (≥6 METs), with moderate activities typically falling between 3-6 METs. According to the most recent and highest quality study 1, examples of moderate-intensity physical activity (3–6 METs) include brisk walking, slow cycling, recreational swimming, and gardening, while vigorous-intensity physical activity (>6 METs) includes running, fast cycling, fast swimming, and competitive sports. METs are useful for exercise prescription because they provide a way to compare different activities and tailor exercise programs to individual fitness levels 1. Understanding exercise in terms of METs can help individuals gauge whether they're meeting physical activity guidelines, which typically recommend accumulating activities that equal 500-1000 MET-minutes per week for health benefits. The concept is based on the physiological principle that higher intensity activities require more oxygen consumption and energy expenditure, creating greater cardiovascular and metabolic demands on the body.

Some key points to consider when using MET values include:

• Sedentary behavior is defined as any waking behavior characterized by an energy expenditure ≤1.5 METs while in a sitting, reclining, or lying posture 1
• Light activities like casual walking might be 2-3 METs, while moderate activities like brisk walking are typically 3-6 METs, and vigorous activities like running can be 6+ METs 1
• Healthcare providers often use MET values to prescribe appropriate exercise intensity for patients, especially those with cardiovascular conditions 1
• The relationship between physical activity and outcomes is curvilinear, with the largest gains yielded from an inactive to a mild or moderately active lifestyle 1

Overall, using MET values can help individuals and healthcare providers make informed decisions about exercise intensity and duration to improve health outcomes.

From the Research

Definition of Exercise Metabolic Equivalent of Task (MET) Values

• One metabolic equivalent (MET) is defined as the amount of oxygen consumed while sitting at rest, equal to 3.5 ml O2 per kg body weight x min 2
• The MET concept represents a simple, practical, and easily understood procedure for expressing the energy cost of physical activities as a multiple of the resting metabolic rate 2
• The energy cost of an activity can be determined by dividing the relative oxygen cost of the activity (ml O2/kg/min) by 3.5 2

Limitations of MET Values

• The 1-MET value of 3.5 ml O2 x kg(-1) x min(-1) overestimates the actual resting VO2 value on average by 35%, and the 1-MET of 1 kcal/h overestimates resting energy expenditure by 20% 3
• The MET concept does not apply well to all individuals, and height, weight, and resting metabolic rate (RMR) should be considered when estimating energy cost of physical activity 4
• Adiposity confounds MET values, and lean mass proportional measures of energy expenditure would enable a more truthful choice to assess physical activity 5

Clinical Applications of MET Values

• METs are routinely employed as a guide to exercise training and activity prescription and to categorize cardiorespiratory fitness (CRF) 6
• However, there are inherent limitations to the concept, as well as common misapplications, and CRF and the patient's capacity for physical activity are often overestimated and underestimated, respectively 6
• Moderate-to-vigorous physical activity, which corresponds to ≥3 METs, may increase MET capacity and decrease the risk of future cardiac events 6