The Metabolic Equivalent of Task (MET) provides a standardized way to measure the energy cost of physical activities relative to rest. It is a ratio that compares a person’s working metabolic rate to their resting metabolic rate. Understanding this measure allows for the quantification of physical activity, transforming time spent on exercise into a universal unit of volume. This framework helps people assess both their weekly activity volume and their individual physiological fitness capacity.
Understanding the MET Unit
The MET unit establishes a baseline for energy expenditure by setting 1 MET as the amount of energy consumed while sitting quietly. This resting metabolic rate is conventionally equated to consuming 3.5 milliliters of oxygen per kilogram of body weight each minute. All other activities are then assigned a MET value that represents a multiple of this resting rate. For instance, an activity rated at 3 METs requires three times the energy expenditure of sitting still.
The intensity of physical activity is categorized by its MET value. Light-intensity activity is defined as anything less than 3 METs, which includes gentle activities like slow walking. Moderate-intensity activities fall within the range of 3 to 5.9 METs, such as a brisk walk. Activities that require 6 METs or more are classified as vigorous-intensity, encompassing exercises like jogging or competitive sports.
Achieving Health Guidelines Through MET-Minutes
To determine the total volume of physical activity completed over a period, the concept of “MET-minutes” is used. This is calculated by multiplying the MET value of an activity by the number of minutes it was performed. For example, a 30-minute brisk walk at 4 METs totals 120 MET-minutes, which is equivalent to a shorter 15-minute run at 8 METs. This allows for the comparison of different activities, recognizing that higher intensity for a shorter duration can be equivalent to lower intensity for a longer duration.
Public health recommendations for substantial health benefits are often stated in minutes of moderate or vigorous activity per week. Translating these minutes into MET-minutes provides a single, actionable goal for the total dose of activity. Adults are advised to achieve a total of approximately 500 to 1,000 MET-minutes of activity each week.
This range is equivalent to completing the minimum recommendation of 150 minutes of moderate-intensity activity or 75 minutes of vigorous-intensity activity per week. The target of 500 to 1,000 MET-minutes per week acts as the general benchmark for a good level of physical activity volume. Achieving this volume is associated with reduced risks for various health outcomes, including cardiovascular disease. For those aiming for even greater health benefits, exceeding 1,000 MET-minutes provides additional risk reduction.
Assessing Personal Fitness Capacity with MET Scores
Beyond measuring activity volume, MET scores are also applied to assess an individual’s maximal aerobic or functional fitness capacity. This is often done clinically, such as during a maximal exercise stress test, where the peak MET level achieved reflects the body’s maximum ability to use oxygen. This maximum capacity is closely related to a person’s VO2 max, a measure of cardiovascular fitness.
Higher maximal MET scores are strongly associated with better cardiovascular health and a lower risk of future cardiac events. A peak MET score of less than 5 is considered poor and may indicate an increased health risk. Achieving a peak MET score of 7 to 10 is considered a good functional capacity for the average adult, while a score of 12 or more is excellent.
The specific good MET score varies with age and sex because maximal aerobic capacity naturally declines over time. For instance, a non-trained man may have a good score around 10 METs, while a non-trained woman might reach 8 METs.
For younger, highly trained individuals, maximal MET scores can exceed 15 or even 20, demonstrating a significantly higher physiological reserve. Improving one’s maximal MET capacity, even by a single unit, can lower the risk of heart disease and mortality by 10% to 20%.