IPAQ MET Categories: Understanding Walking, Moderate, and Vigorous Physical Activity

What are the met categories for IPAQ?

The International Physical Activity Questionnaire (IPAQ) utilizes specific Metabolic Equivalent of Task (MET) categories—specifically 3.3 METs for walking, 4.0 METs for moderate physical activity, and 8.0 METs for vigorous physical activity—to quantify and standardize the energy expenditure associated with different levels of physical activity reported by individuals.

Understanding IPAQ and METs

The International Physical Activity Questionnaire (IPAQ) is a widely used instrument designed to provide a standardized method of assessing physical activity levels in diverse populations. It collects information on various types of activity, including walking, moderate-intensity activities, and vigorous-intensity activities, across different domains such as work, transportation, household chores, and leisure time. To translate the reported activity into a quantifiable measure of energy expenditure, IPAQ relies on Metabolic Equivalents of Task (METs).

A MET is a physiological measure expressing the energy cost of physical activities. One MET is defined as the energy expended while sitting quietly, equivalent to 3.5 milliliters of oxygen consumed per kilogram of body weight per minute (mL/kg/min). Essentially, it represents the ratio of a person's working metabolic rate to their resting metabolic rate. For example, an activity with a MET value of 4 means that a person expends four times the energy they would at rest while performing that activity. By assigning specific MET values to different types of activities, IPAQ can calculate an individual's total physical activity in MET-minutes per week, allowing for comparisons and classifications of activity levels.

The IPAQ MET Categories

IPAQ employs three primary MET categories, each assigned a standardized value, to quantify the reported physical activities:

• Walking (WALK): 3.3 METs
  • This category encompasses walking for transportation, at work, at home, or during leisure time. The 3.3 MET value represents the average energy cost of walking at a moderate pace, typically around 3-4 miles per hour (4.8-6.4 km/h). This standardized value allows for a consistent calculation of energy expenditure across all reported walking activities.
• Moderate Physical Activity (MOD): 4.0 METs
  • Moderate activities are those that require more effort than walking but do not lead to a substantial increase in breathing rate or heart rate. Individuals can typically carry on a conversation during moderate activity. Examples include cycling at a regular pace, general gardening, sweeping, or light to moderate lifting. The 4.0 MET value is an average assigned to these types of activities.
• Vigorous Physical Activity (VIG): 8.0 METs
  • Vigorous activities are characterized by a significant increase in breathing and heart rate, making it difficult to hold a conversation. These activities demand a high level of effort and cause sweating. Examples include running, fast cycling, vigorous swimming, competitive sports, heavy lifting, or strenuous aerobics. The 8.0 MET value reflects the higher energy expenditure associated with these intense activities.

It is important to note that IPAQ also collects data on sedentary behavior, specifically time spent sitting, which is reported in hours and minutes. While sedentary time is a critical component of overall activity assessment, it is not assigned a MET value for the purpose of calculating active energy expenditure, but rather represents a lack of activity.

Calculating Physical Activity with IPAQ METs

The assigned MET values are crucial for calculating an individual's total physical activity score in MET-minutes per week. The calculation for each type of activity is as follows:

• MET-minutes/week = MET value × minutes of activity per day × days per week

For example, if an individual reports walking for 30 minutes, 5 days a week: 3.3 (METs for walking) × 30 (minutes/day) × 5 (days/week) = 495 MET-minutes/week from walking.

These calculations are performed for walking, moderate activity, and vigorous activity, and then summed to provide a total MET-minutes/week score. This aggregated score allows for the classification of individuals into different physical activity categories (e.g., low, moderate, high), which can then be used for public health surveillance and research.

Interpreting IPAQ Results and Health Implications

The standardized MET categories enable IPAQ to provide a quantitative measure of physical activity, which is vital for understanding population-level activity trends and the relationship between physical activity and health outcomes. Public health guidelines often recommend specific targets for moderate and vigorous physical activity, usually expressed in minutes per week. By converting reported activities into MET-minutes, IPAQ data can be directly compared against these recommendations, helping to identify individuals or groups who may be at higher risk due due to insufficient activity.

For instance, the recommended 150 minutes of moderate-intensity activity per week (equivalent to 150 minutes × 4.0 METs = 600 MET-minutes/week) or 75 minutes of vigorous-intensity activity per week (equivalent to 75 minutes × 8.0 METs = 600 MET-minutes/week) can be directly assessed using IPAQ scores.

Limitations and Considerations

While the MET categories in IPAQ offer a robust framework for activity assessment, it's important to acknowledge certain limitations:

• Self-Report Bias: IPAQ relies on an individual's recall and estimation of their physical activity, which can be subject to over- or under-reporting.
• Generalized MET Values: The assigned MET values are averages. The actual energy expenditure for an individual performing a "moderate" or "vigorous" activity can vary based on their fitness level, body composition, and specific intensity within that category.
• Contextual Factors: The questionnaire may not fully capture the nuances of all physical activities or the specific context in which they are performed.
• Difficulty in Interpretation for Complex Activities: For activities that combine elements of different intensities, assigning a single MET value can be challenging.

Despite these limitations, the use of standardized MET categories within IPAQ remains an invaluable tool for researchers, public health professionals, and fitness educators to assess and promote physical activity across populations. Understanding these categories is fundamental to accurately interpreting IPAQ data and applying its insights to health and wellness strategies.