The numbers that flash across a treadmill’s display often include a metric called MET, which stands for Metabolic Equivalent of Task. This value provides a standardized, objective measure of the energy demand an activity places on the body. Understanding the MET value helps translate the effort exerted on the machine into a universal physiological language, representing the ratio of your working metabolic rate compared to your resting metabolic rate.
Defining the Metabolic Equivalent of Task
The MET system is built upon a single, fixed reference point: 1 MET. This value represents the energy expended while sitting quietly at rest, defining the baseline metabolism. Scientists standardized this resting metabolic rate by establishing a specific oxygen consumption rate. One MET is equivalent to consuming 3.5 milliliters of oxygen per kilogram of body weight per minute.
Any physical activity is measured as a multiple of this resting rate. For instance, an activity rated at 4 METs requires the body to expend four times the energy it would use while at rest. Because the 1 MET standard is based on a fixed physiological value, it provides a consistent measure of energy expenditure for any activity, regardless of an individual’s personal fitness level.
How METs Measure Exercise Intensity
The MET value displayed on a treadmill serves as an immediate indicator of the workout’s intensity and the physical effort required. Health organizations use specific MET ranges to categorize physical activity into three main levels. Activities between 1.1 and 2.9 METs, such as a slow stroll, are classified as light intensity.
Moderate-intensity activities typically fall between 3.0 and 5.9 METs. For a treadmill user, this range often includes brisk walking at a speed of about three miles per hour, which is commonly rated around 3.4 METs. Increasing the incline or speed to a more challenging level pushes the MET value higher, signifying a greater demand on the cardiovascular system.
Activity levels that reach 6.0 METs or more are considered vigorous intensity. Running at a pace of six miles per hour, for example, typically corresponds to an estimated MET value of 8.4. These higher numbers indicate that the body is utilizing oxygen and energy at a significantly faster rate to meet the demands of the exercise.
METs are also useful for tracking progress toward weekly activity goals, which are often expressed in “MET-minutes.” The total MET-minutes are calculated by multiplying the MET value of the activity by the number of minutes spent performing it. A common goal for significant health benefits is achieving 500 to 1,000 MET-minutes per week. This metric allows a user to accurately compare a long, moderate-intensity walk with a shorter, vigorous-intensity run.
Translating METs into Calorie Expenditure
The final practical step for a treadmill user is converting the MET value into an estimate of total calories burned. While the MET value itself is a standardized measure of intensity, the calorie calculation requires individual input, specifically body weight. The formula used to estimate energy expenditure in calories per minute is: METs \(\times 3.5 \times\) body weight in kilograms \(\div 200\).
The constant 3.5 in the equation represents the standardized oxygen consumption rate of 1 MET. This formula demonstrates why two people performing the exact same workout on a treadmill—same speed and incline, same MET value—will burn different amounts of calories. The individual with a higher body mass requires more energy to move their body, leading to a higher calculated calorie expenditure.
The calorie count displayed on a treadmill is an estimate based on this standardized MET calculation. This is why it may differ from a value provided by a heart rate monitor or fitness watch. Treadmills often do not accurately know the user’s weight, or they may use a default value, affecting the final calorie total. Therefore, the MET value provides the most consistent measure of the objective work being done.