Physical Activity Questionnaires: Scoring, Interpretation, and Best Practices

How to Score Physical Activity Questionnaires

Scoring physical activity questionnaires involves standardized protocols, often utilizing Metabolic Equivalent (MET) values, frequency, and duration to quantify an individual's reported activity into interpretable metrics, such as MET-minutes per week or categorical classifications, enabling comparison against health guidelines and tracking progress.

Understanding Physical Activity Questionnaires (PAQs)

Physical Activity Questionnaires (PAQs) are self-report or interviewer-administered tools designed to assess an individual's typical physical activity levels over a specified period (e.g., the last 7 days, a typical week, or a month). They serve as cost-effective and practical instruments for large-scale epidemiological studies, clinical assessments, and personal fitness evaluations.

Types of PAQs and Common Data Points: PAQs vary significantly in their length, complexity, and the specific domains of activity they capture. Common types include:

• Global PAQs: Such as the International Physical Activity Questionnaire (IPAQ) and the Global Physical Activity Questionnaire (GPAQ), which assess activity across multiple domains (work, transport, domestic, leisure).
• Domain-Specific PAQs: Focusing on particular types of activity, like leisure-time physical activity or occupational activity.
• Single-Item Screens: Quick questions to gauge overall activity levels.

Regardless of the type, most PAQs collect data on:

• Frequency: How many days per week or times per day an activity is performed.
• Duration: How long each session of activity lasts.
• Intensity: The perceived effort level (light, moderate, vigorous) or the specific type of activity that implies intensity.

General Principles of Scoring PAQs

The underlying goal of scoring PAQs is to transform raw, self-reported data into quantifiable metrics that can be analyzed and interpreted. This process relies on standardized methodologies to ensure consistency and comparability.

• Standardized Protocols: Each validated PAQ comes with specific, detailed scoring instructions. Adhering strictly to these protocols is paramount to maintaining the validity and reliability of the data. Deviations can lead to inaccurate results.
• Metabolic Equivalents (METs): A cornerstone of PAQ scoring is the use of METs. One MET is defined as the energy cost of sitting quietly and is equivalent to an oxygen uptake of 3.5 ml/kg/min.
  • Light-intensity activities: Typically assigned MET values between 1.5 and 2.9.
  • Moderate-intensity activities: Assigned MET values between 3.0 and 5.9.
  • Vigorous-intensity activities: Assigned MET values of 6.0 or higher.
  • By assigning MET values to reported activities, researchers can estimate the energy expenditure associated with different types and intensities of physical activity.
• Calculating Activity Volume: The most common metric for quantifying physical activity is MET-minutes per week. This is calculated by multiplying the MET value of an activity by its duration (in minutes) and frequency (in days per week).
  • MET-minutes/week = MET value x minutes/session x sessions/week
• Handling Missing Data and Outliers: Scoring protocols usually include guidelines for managing incomplete responses or implausible data (e.g., reporting 24 hours of vigorous activity per day). This often involves imputation methods, data capping, or excluding invalid responses.

Step-by-Step Guide to Scoring Common PAQs: The IPAQ Example

The International Physical Activity Questionnaire (IPAQ) is one of the most widely used PAQs globally. Its scoring protocol provides a clear illustration of the principles outlined above. The following steps are based on the IPAQ's official scoring guidelines for the long form, which typically covers walking, moderate-intensity, and vigorous-intensity activities in four domains (work, transport, domestic, leisure-time).

Step 1: Data Cleaning and Truncation

• Invalid Entries: Any "don't know" or "refused" responses are treated as missing data.
• Minimums: Any reported duration less than 10 minutes for a given activity (walking, moderate, vigorous) should be re-coded to zero. Activities lasting less than 10 minutes are generally not considered health-enhancing.
• Maximums: Capping is applied to extreme values. For instance, any single activity duration reported over 3 hours (180 minutes) is truncated to 180 minutes. The total weekly physical activity (sum of all activities) is capped at 16 hours/day (960 minutes/day) or 1920 MET-minutes/day (which is 16 hours 60 min/hr 2 METs for light activity, or 16 hours 60 min/hr 2 METs for light activity, or if we use 16 hours 60 min/hr 10 METs, it would be too high). For IPAQ, the common cap is 16 hours/day total activity across all domains and intensities, or 960 minutes/day. More precisely, the total weekly physical activity is capped at 16 hours/day * 7 days = 112 hours/week, or 6720 minutes/week.

Step 2: Assigning MET Values The IPAQ uses standard MET values:

• Walking: 3.3 METs
• Moderate Physical Activity: 4.0 METs
• Vigorous Physical Activity: 8.0 METs

Step 3: Calculating MET-minutes for Each Activity Domain For each domain (work, transport, domestic, leisure) and each intensity (walking, moderate, vigorous), calculate the MET-minutes per week:

• MET-minutes/week = (Days/week) x (Minutes/day) x (MET value)

Step 4: Summing for Total Physical Activity Sum the MET-minutes/week across all domains and intensities to get a Total Physical Activity MET-minutes/week score.

Step 5: Categorical Scoring (Optional, but common) The IPAQ also allows for categorization of individuals into three levels:

• Low: Does not meet criteria for Moderate or High activity.
• Moderate:
  • 3 or more days of vigorous activity of at least 20 minutes per day OR
  • 5 or more days of moderate-intensity activity and/or walking of at least 30 minutes per day OR
  • 5 or more days of any combination of walking, moderate-intensity, or vigorous-intensity activities achieving a minimum of 600 MET-minutes/week.
• High:
  • Vigorous-intensity activity on at least 3 days and accumulating at least 1500 MET-minutes/week OR
  • 7 or more days of any combination of walking, moderate-intensity or vigorous-intensity activities accumulating at least 3000 MET-minutes/week.

Interpreting the Scores

Once a PAQ has been scored, the resulting metrics need to be interpreted within a relevant context.

• Comparison to Health Guidelines: The most common use is to compare an individual's activity levels to established public health recommendations, such as those from the World Health Organization (WHO) or national health agencies. For adults, these typically recommend at least 150-300 minutes of moderate-intensity aerobic activity per week, or 75-150 minutes of vigorous-intensity aerobic activity, or an equivalent combination.
• Categorization: Placing individuals into "low," "moderate," or "high" activity categories can be useful for population health surveillance, identifying at-risk groups, or setting general fitness goals.
• Tracking Progress: For individuals, repeated PAQ assessments can track changes in activity over time, helping to monitor the effectiveness of interventions or lifestyle changes.
• Research Applications: In research, scores are used to correlate physical activity with health outcomes, evaluate intervention efficacy, or describe population activity patterns.

Challenges and Considerations in PAQ Scoring

While PAQs are valuable, their scoring is subject to several inherent challenges:

• Recall Bias: Individuals may inaccurately recall the frequency, duration, or intensity of their activities, leading to over- or under-reporting.
• Social Desirability Bias: Respondents may report higher levels of activity than they actually perform to align with perceived healthy norms.
• Subjectivity of Intensity: Perceived intensity can vary greatly between individuals, making the assignment of fixed MET values an approximation.
• Cultural and Contextual Differences: The interpretation of activities (e.g., "walking") and their associated energy expenditure might differ across cultures or environments.
• Data Cleaning Complexity: Thorough data cleaning, including managing outliers and missing data, requires careful attention to avoid skewing results.
• Validation: PAQs require rigorous validation against objective measures (e.g., accelerometers) to ensure their accuracy in different populations.

Best Practices for Researchers and Practitioners

To maximize the utility and accuracy of PAQ scoring:

• Adhere Strictly to Protocols: Always use the official, validated scoring algorithms for the specific PAQ being administered. Do not create ad-hoc scoring methods.
• Train Administrators: Ensure that those administering the questionnaire are well-trained on how to explain the questions clearly and handle common queries, minimizing misinterpretation by respondents.
• Provide Clear Instructions to Respondents: Emphasize the importance of accurate recall and provide examples of different intensity levels.
• Consider Data Triangulation: Whenever feasible, supplement PAQ data with objective measures (e.g., accelerometers, pedometers) or other assessment methods to provide a more comprehensive and accurate picture of physical activity.
• Be Transparent About Limitations: Acknowledge the self-report nature of the data and its potential biases when interpreting and disseminating findings.
• Use Appropriate Software: Utilize statistical software or dedicated scoring tools to automate calculations, reduce human error, and apply complex cleaning rules efficiently.

Conclusion

Scoring physical activity questionnaires is a crucial step in transforming self-reported data into meaningful, quantifiable metrics. By understanding the principles of METs, adhering to standardized protocols, and carefully considering the inherent challenges, fitness educators, researchers, and health professionals can effectively utilize PAQs to assess physical activity levels, inform interventions, and contribute to a better understanding of public health. While not without limitations, PAQs remain an indispensable tool in the field of exercise science and kinesiology.