METs: Definition, Importance, and How They Are Used in Health and Fitness

What METs Means?

METs, or Metabolic Equivalents of Task, are a standardized scientific measure used to express the energy cost of physical activities, quantifying the intensity of an activity relative to your resting metabolic rate.

What Are METs? The Core Definition

At its foundation, a MET (Metabolic Equivalent of Task) provides a simple, universal way to express the energy expenditure of physical activities. It quantifies how much energy your body is using during an activity compared to the energy it uses while at complete rest.

• 1 MET is defined as the energy expenditure while sitting quietly, equivalent to consuming 3.5 milliliters of oxygen per kilogram of body weight per minute (3.5 ml O2/kg/min). This represents your basal metabolic rate (BMR) or resting metabolic rate (RMR) for a typical adult.
• Activities with higher MET values demand more oxygen and, consequently, more energy from your body, indicating a higher intensity. For example, an activity rated at 4 METs means you are expending four times the energy compared to when you are at rest.

The concept of METs is crucial because it allows for a standardized comparison of physical activity intensity across different individuals, regardless of their body size or fitness level, by normalizing energy expenditure to a resting baseline.

Why Are METs Important? Applications in Health and Fitness

Understanding METs is vital for several reasons, impacting public health recommendations, exercise prescription, and individual fitness goals:

• Quantifying Exercise Intensity: METs provide an objective measure of how hard your body is working during an activity. This allows for consistent communication and comparison of activity levels across research studies, clinical settings, and fitness programs.
• Public Health Guidelines: Major health organizations, such as the American College of Sports Medicine (ACSM) and the World Health Organization (WHO), use METs to define recommended levels of physical activity. For instance, adults are typically advised to accumulate 500-1000 MET-minutes of moderate-to-vigorous physical activity per week to achieve significant health benefits.
• Exercise Prescription: For fitness professionals, METs help in designing appropriate exercise programs. By knowing the MET value of various activities, trainers can prescribe specific exercises that meet a client's intensity goals, whether for weight management, cardiovascular health, or performance enhancement.
• Risk Assessment and Disease Prevention: Regular engagement in activities with specific MET values is consistently linked to a reduced risk of chronic diseases like cardiovascular disease, type 2 diabetes, certain cancers, and obesity. Tracking METs allows individuals and clinicians to assess activity levels against these health benchmarks.

How Are METs Measured and Used?

While direct measurement of oxygen consumption (indirect calorimetry) is a precise scientific method, for practical purposes, MET values for thousands of activities have been compiled into comprehensive compendiums, most notably the Compendium of Physical Activities.

• Compendium of Physical Activities: This widely used resource lists MET values for a vast array of common daily activities, sports, and exercises. These values are typically derived from research studies measuring the average oxygen consumption of participants performing those activities.
• Categories of Intensity: METs classify activity intensity:
  • Light-intensity activities: Less than 3 METs (e.g., slow walking, light housework, standing).
  • Moderate-intensity activities: 3 to 6 METs (e.g., brisk walking, swimming at a moderate pace, cycling at 10-12 mph, doubles tennis).
  • Vigorous-intensity activities: Greater than 6 METs (e.g., running, jumping rope, competitive sports, heavy weightlifting).
• MET-Minutes and MET-Hours: To quantify total physical activity over time, METs are often multiplied by the duration of the activity. For example, walking at 3 METs for 30 minutes equals 90 MET-minutes (3 METs * 30 minutes). This aggregate measure is crucial for meeting public health recommendations.

Examples of Activities and Approximate MET Values:

• Sleeping: 0.9 METs
• Watching TV (sitting): 1.0 METs
• Walking, slow pace (2.0 mph): 2.0 METs
• Walking, brisk pace (3.0 mph): 3.5 METs
• Cycling, moderate (10-12 mph): 6.0 METs
• Swimming, moderate pace: 6.0-7.0 METs
• Weightlifting, vigorous effort: 6.0 METs
• Running (6.0 mph): 10.0 METs
• Jumping rope: 11.0 METs

Limitations and Considerations of METs

While invaluable, METs are not without limitations:

• Individual Variability: MET values are averages. An individual's actual energy expenditure can vary based on their fitness level, body composition, age, gender, and even their efficiency of movement. A highly fit individual might expend less energy (and thus fewer METs) than a deconditioned individual performing the same task.
• Environmental Factors: External conditions like temperature, humidity, and altitude can influence the physiological response to exercise, potentially altering the actual energy cost beyond the standard MET value.
• Activity Specifics: Even within a single activity type, variations exist. For instance, walking uphill or carrying a load will increase the MET value compared to walking on flat ground.
• Not a Direct Measure of Effort: METs measure physiological demand, not necessarily perceived exertion. Two people might achieve the same MET value for an activity, but one might find it easy while the other finds it very challenging. Therefore, using Rate of Perceived Exertion (RPE) scales alongside METs can provide a more comprehensive picture of exercise intensity.

Incorporating METs into Your Fitness Journey

For fitness enthusiasts, trainers, and students of kinesiology, METs offer a powerful tool:

• Understand Your Current Activity: Use the concept of METs to objectively assess your daily and weekly physical activity levels. Many fitness trackers now provide estimated MET values or MET-minutes.
• Set Informed Goals: Align your activity goals with public health guidelines (e.g., aiming for at least 500 MET-minutes/week of moderate-to-vigorous activity).
• Diversify Your Training: Recognize that different activities contribute differently to your overall MET-minute accumulation. Incorporate a mix of light, moderate, and vigorous activities to achieve a well-rounded fitness regimen.
• Communicate Effectively: When discussing exercise with clients or peers, using METs provides a common language for intensity and volume.
• Consult Professionals: If you're unsure how to apply METs to your specific health and fitness goals, consult with a certified personal trainer, exercise physiologist, or healthcare provider.

Conclusion: The Value of METs in a Holistic View

METs serve as a cornerstone in exercise science, providing a standardized, accessible metric for understanding and quantifying the energy cost of physical activity. While acknowledging their inherent averages and individual variability, their utility in public health recommendations, exercise prescription, and personal fitness tracking remains unparalleled. By understanding what METs mean and how they apply to your activities, you gain a powerful tool to navigate your fitness journey, optimize your training, and ultimately, improve your long-term health.