measuring physical activity: tools and indicators

Measuring Physical Activity:Tools and Indicators

Bill Kohl

University of Texas Health Science Center – HoustonSchool of Public Health

University of Texas at AustinDepartment of Kinesiology and Health Education

19th International Physical Activity and Public Health Training Course

Palm Beach Aruba, June 2012

Objectives

• Conceptual framework

• Key issues in physical activity assessment

• Overview of physical activity surveillance

Phys

iolo

gica

l, Ps

ycho

soci

al a

nd E

nviro

nmen

tal C

orre

late

s

Leisure

TransportHousehold DomesticSelf-Care

Occupation

Physical Activity

Phys

iolo

gica

l Att

ribut

es

Behavior

Sleep

NonDiscretionary

Sedentary

Discretionary

Human Movement

Characteristic Outcome

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

Leisure

TransportHousehold DomesticSelf-Care

Occupation

Physical Activity

ExerciseSpecific Activity Type

e.g., soccer, lifting heavy boxes or children, walking

Intensity Categorye.g., light, moderate, vigorous

Recall Cue

Frequency

Characteristic

Intensity

Duration

Pattern

Gabriel et al 2011

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

Methodological Concepts

• Validation standards in physical activity assessment

• Energy expenditure• Physical fitness• Physical activity• Body composition

Variety of methods of each standard

Methodological Concepts

• Practicality• Non-reactivity

Physical Activity Assessment

• Calorimetry• Doubly labeled water• Direct observation• Job classification• Monitoring• Self report• Dietary questionnaires

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

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

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

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

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

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

Incr

easi

ng p

reci

sion

Decreasing difficulty

Self-Report

Monitoring

Direct Observation

Indirect Calorimetry

Doubly-Labeled Water

Direct Calorimetry

Physical activity assessment cascade

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

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?

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

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

Caution!

SurveillanceVersus

Assessment

Public Health Physical Activity Surveillance – The Ideal?

Individuals

Policy

EnvironmentalDeterminants

Non-public health data sources

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.

International PA surveillance

International trends in “Regular Physical Activity”: Adults

0

10

20

30

40

50

60

70%

80 82 84 86 88 90 92 94 96 98

18+, 3+ kkd

18+, 1625+ kwk

18+, vigorous

15+, 2+/wk

18+, 3/wk

Finland

Canada

Scotland

Australia

USA

Australia18+, 150m/wk, 5 sessions

With thanks to Cora Craig, CFLRI, Ottawa

IPAQINTERNATIONAL PHYSICAL ACTIVITY

QUESTIONNAIRE

first steps towards global measurement of physical activity

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

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

Proximo?

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

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

GPAQGPAQ Strengths+ domains+ quantifies exposure+ cross cultural application

GPAQ Weaknesses+ new measure+ needs testing

IPAQ LONG IPAQ SHORTJob related = 7; Transport = 6; Home = 6; Recreation = 6; Sitting = 2Total n=27

6 items on PA across the 4Domains; sitting = 1Total n=7

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

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

Public Health Physical Activity Surveillance – Environmental Data

EnvironmentalDeterminants

Urban designDensityAccess to destinationsConnectivityAesthetics

Land useGreen space

TransportationInfrastructure, Public transit

SafetyPerceptions

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

Year

Perc

ent

• Written codes, written standards, unwritten norms• Legislation (enacted, pending, defeated – level?)

Urban designLand useTransportationSafety

• Organizational policySchoolsWorksitesNeighborhood

Public Health Physical Activity Surveillance – Policy-level Data

Policy

Physical Activity Policy Research Framework

  Outcomes of Policy

Develop and Implement Policy

Determinants of Policy

Identify Policies

LocalRegional

StateNational

Research Type

Sector

TransportationParks/Public Spaces

WorksiteSchool Level

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

Year

Perc

ent

Initial legislative topic areas

• Urban design• Land use• Transportation• Community physical activity

promotion• Physical education

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)?

Public Health Physical Activity Surveillance – The Ideal?

Media attention“Critical mass”Industry and marketing data

individual and aggregateTrade associationsOthers?

Non-public health data sources

Public Health Physical Activity Surveillance – The Ideal?

Other Issues:Definitions, definitions, definitionsDataLevel of monitoring?Type of system?How will data be used?PeriodicityAggregation to conduct analyses with other types of surveillance dataLocal, State and Regional needs

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.

Public Health Physical Activity Surveillance – The Ideal?

Individuals

Policy

EnvironmentalDeterminants

Non-public health data sources

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)?

Absolute changes between 1969 and 2001 for School Transport – United States

Diff

eren

ce

Ham, et al., Unpublished