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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


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


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

19 Physical Activity Assessment: Future Directions Intra-individual variation in physical activity assessment: How many days are enough? Methods for assessing non-aerobic activities How can existing physical activity assessment instruments be adapted/adopted into different populations and subgroups?


21 The Uses of Public Health Chronic Disease and Behavioral Surveillance Systems Quantify magnitude of health problem Describe natural history of disease Detect “outbreaks” Document Person, Place and Time Test hypotheses Evaluate intervention measures (control/prevention) Detection of changes in health practices Policy and planning Adapted from Thacker, 1994

22 Steps in Planning a Public Health Surveillance System Establish objectives Develop case definitions Determine data source(s) and mechanism of collection Develop instruments Field-test methods – refine as necessary Develop and test analytic approaches Develop and test dissemination mechanisms Evaluate analysis and interpretation Adapted from Teutsch, 1994


24 Caution! Surveillance Versus Assessment

25 Public Health Physical Activity Surveillance – The Ideal? Individuals Policy Environmental Determinants Non-public health data sources

26 Public Health Physical Activity Surveillance – Individual-level data Individuals Frequency Intensity Duration Mode Domains “Meeting” recommendations Health Objectives eg. BRFSS; YRBS; HANES; NHIS; NHTS, etc.


28 International PA surveillance

29 International trends in “Regular Physical Activity”: Adults With thanks to Cora Craig, CFLRI, Ottawa

30 IPAQ I NTERNATIONAL PHYSICAL ACTIVITY QUESTIONNAIRE first steps towards global measurement of physical activity

31 IPAQ group : measurement and development tasks 1997-2004 Phase I dreaming up a global measure 1997-8 Phase II testing, formative work on questions internationally Phase III formal reliability and validity testing in 11 countries 2000 Phase IV International prevalence study – testing it in the field 2003-4

32 IPAQ summary Reasonable measurement properties First internationally comparable studies used IPAQ – initially in Europe only Short and long versions IPS - prevalence differences noted Differences in sitting time Methodological issues with international work An example of good PAPH collaboration of national physical activity scientists

33 Proximo? IPAQ developed 1998-2000 IPAQ reliability and validity study IPAQ prevalence study But IPAQ was not enough …..

34 Development of GPAQ Half way between IPAQ short form and IPAQ long form STEPwise approach to NCD risk Factor surveillance (“STEPS”) especially for developing countries

35 GPAQ GPAQ Strengths + domains + quantifies exposure + cross cultural application GPAQ Weaknesses + new measure + needs testing IPAQ LONG IPAQ SHORT Job related = 7; Transport = 6; Home = 6; Recreation = 6; Sitting = 2 Total n=27 6 items on PA across the 4 Domains; sitting = 1 Total n=7

36 Developments Portugal meeting 2005 and Rome meeting 2007: consensus re findings of GPAQ- discussion of GPAQ in the field Feedback from STEPS countries; Suggestions for change Remaining issues –How well GPAQ or IPAQ reflects PA patterns in sub populations in developing countries –Recall of time and understanding of 10 minute minimum –More research warranted in developing countries / continue to build capacity

37 Current Global PA surveillance WHO has canvassed across countries (May 2005) and made slight changes to GPAQ - new version is called GPAQ2 So global surveillance has 2 currently used PA instruments “IPAQ” adapted countries will use IPAQ, and “GPAQ experienced” countries continue to use GPAQ / GPAQ2 Other countries with existing PA surveillance will likely rely on existing systems


39 Public Health Physical Activity Surveillance – Environmental Data Environmental Determinants Urban design Density Access to destinations Connectivity Aesthetics Land use Green space Transportation Infrastructure, Public transit Safety Perceptions

40 Prevalence environmental determinants and supports for physical activity, US 1990-1998 Year Percent

41 Written codes, written standards, unwritten norms Legislation (enacted, pending, defeated – level?) Urban design Land use Transportation Safety Organizational policy Schools Worksites Neighborhood Public Health Physical Activity Surveillance – Policy-level Data Policy

42 Physical Activity Policy Research Framework Outcomes of Policy Develop and Implement Policy Determinants of Policy Identify Policies Local Regional State National Research Type Sector Transportation Parks/Public Spaces Worksite School Level

43 Prevalence of policy supports for physical activity, US 1990-1998 Year Percent

44 Initial legislative topic areas Urban design Land use Transportation Community physical activity promotion Physical education

45 Upcoming Challenges Emerging research Level? Local versus state (and linkages) Indices and weighting Appropriations Measuring change Legislative policies, regulations, organizational policies, social norms? Appropriate outcome data How will data be most useful (and to whom)?

46 Public Health Physical Activity Surveillance – The Ideal? Media attention “Critical mass” Industry and marketing data individual and aggregate Trade associations Others? Non-public health data sources

47 Public Health Physical Activity Surveillance – The Ideal? Other Issues: Definitions, definitions, definitions Data Level of monitoring? Type of system? How will data be used? Periodicity Aggregation to conduct analyses with other types of surveillance data Local, State and Regional needs

48 Public Health Physical Activity Surveillance – The Ideal? Surveillance systems must: Address a measurable construct. Be able to quantify changes as they occur. Apply to the majority of the population of interest. Must address public health issues that are changeable. Be responsive to new data and methodolgic advances.

49 Public Health Physical Activity Surveillance – The Ideal? Individuals Policy Environmental Determinants Non-public health data sources



52 National Household Transportation Survey (NHTS) Conducted by U.S. D.O.T. Household survey using telephone interviews and a 24-hour travel diary (N=69,817 households) Travel patterns for work, school, and other daily travel were assessed How did the child get to (or from) school? How far is it from home to child’s school (or from child’s school to home)?

53 Absolute changes between 1969 and 2001 for School Transport – United States Difference Ham, et al., Unpublished

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