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Measuring Physical Activity: Tools and Indicators Bill Kohl University of Texas Health Science Center – Houston School of Public Health University of Texas.

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Presentation on theme: "Measuring Physical Activity: Tools and Indicators Bill Kohl University of Texas Health Science Center – Houston School of Public Health University of Texas."— Presentation transcript:

1 Measuring Physical Activity: Tools and Indicators Bill Kohl University of Texas Health Science Center – Houston School of Public Health University of Texas at Austin Department of Kinesiology and Health Education 19 th International Physical Activity and Public Health Training Course Palm Beach Aruba, June 2012

2 Objectives Conceptual framework Key issues in physical activity assessment Overview of physical activity surveillance

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4 Physiological, Psychosocial and Environmental Correlates Leisure Transport Household Domestic Self-Care Occupation Physical Activity Physiological Attributes Behavior Sleep Non Discretionary Sedentary Discretionary Human Movement CharacteristicOutcome Activity-Related Energy Expenditure Energy Expenditure Balance Body Composition Muscular Fitness Flexibility Cardiorespiratory Physical Fitness Thermogenesis Basal (or Resting) Metabolic Rate Health Enhancing Health Compromising Variable Association with Health Outcomes Gabriel et al 2011

5 Leisure Transport Household Domestic Self-Care Occupation Physical Activity Exercise Specific Activity Type e.g., soccer, lifting heavy boxes or children, walking Intensity Category e.g., light, moderate, vigorous Recall Cue Frequency Characteristic Intensity Duration Pattern Gabriel et al 2011

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7 Methodological Concepts Validation standard A predetermined criterion against which the accuracy of the test instrument is measured. The standard is presumably less variable than the test method. Variety of validation standards in physical activity

8 Methodological Concepts Validation standards in physical activity assessment Energy expenditure Physical fitness Physical activity Body composition Variety of methods of each standard

9 Methodological Concepts Practicality Non-reactivity

10 Physical Activity Assessment Calorimetry Doubly labeled water Direct observation Job classification Monitoring Self report Dietary questionnaires

11 Physical Activity Assessment Doubly-labeled water Based on ingestion of water with radioisotopic labeled hydrogen and oxygen atoms Energy expenditure measured by measuring unmetabolized portion of water over period of time Highly accurate Impractical for large studies

12 Physical Activity Assessment Direct Observation Individual observer monitoring a consenting individual for a set period of time Videos and still photos are possible alternatives Summary index of energy expenditure Impractical for large population studies Likely highly reactive

13 Physical Activity Assessment Job Classification Index and ranking of individuals based on energy demands of usual occupation/job title May be less useful in populations where variance in job energy demands is minimal Seasonality, selection, misclassification No indicator of leisure time activity

14 Physical Activity Assessment Monitoring Heart rate monitors, motion sensors, pedometers, accelerometers Assume mathematical relation between measurements and physical activity Many can can measure quantity and intensity of physical activity Recent advances make devices more practical

15 Physical Activity Assessment Self-report Diaries, interviews and self-administered surveys Varying lengths of recall, all assumed to be indicators of “usual” physical activity Varying quality of summary indices May not be transferrable among populations Most often used in population-based research Highly variable and questionnable accuracy

16 Physical Activity Assessment Dietary measures Caloric value of food consumed used as a measure of corresponding energy utilized Assumes energy balance Body weight is confounding factor Expensive and difficult to weigh all food prior to intake for any period of time Intake in free-living populations is highly variable Diet surveys are not practical

17 Increasing precision Decreasing difficulty Self-Report Monitoring Direct Observation Indirect Calorimetry Doubly-Labeled Water Direct Calorimetry Physical activity assessment cascade

18 Physical Activity Assessment: Future Directions Emphasis must be on measuring more than just total “dose”: understanding intensity, frequency, and patterns is critical Methods to assess historical physical activity (recall) are important Accelerometers are likely the most productive future trend in physical activity assessment. More work on electronics is needed