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
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
Characteristic
Outcome
Basal (or Resting)
Metabolic Rate
Leisure
Occupation
Human
Movement
Thermogenesis
Activity-Related Energy
Expenditure
Energy Expenditure
Household
Domestic
Self-Care
Transport
Physical Activity
Sedentary
Non
Discretionary
Gabriel et al 2011
Physiological Attributes
Physiological, Psychosocial and Environmental Correlates
Behavior
Cardiorespiratory
Muscular
Fitness
Flexibility
Balance
Body
Composition
Physical Fitness
Health Enhancing
Discretionary
Health Compromising
Sleep
Variable Association with
Health Outcomes
Frequency
Exercise
Occupation
Specific Activity Type
e.g., soccer, lifting heavy
boxes or children, walking
Intensity
Leisure
Duration
Household
Domestic
Self-Care
Transport
Intensity Category
e.g., light, moderate, vigorous
Pattern
Physical
Activity
Gabriel et al 2011
Recall Cue
Characteristic
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
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Energy expenditure
Physical fitness
Physical activity
Body composition
Variety of methods of each standard
Methodological Concepts
• Practicality
• Non-reactivity
Physical Activity Assessment
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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
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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
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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
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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
Physical activity assessment cascade
Increasing precision
Doubly-Labeled Water
Indirect Calorimetry
Direct Observation
Monitoring
Self-Report
Decreasing difficulty
Direct Calorimetry
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
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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!
Surveillance
Versus
Assessment
Public Health Physical Activity
Surveillance – The Ideal?
Individuals
Non-public health
data sources
Environmental
Determinants
Policy
Public Health Physical Activity
Surveillance – Individual-level data
Individuals
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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
70%
Finland
60
50
Australia
15+, 2+/wk
18+, 150m/wk, 5 sessions
Canada
40
30
Scotland
18+, 3/wk
18+, 3+ kkd
20
Australia
18+, 1625+ kwk
10
USA
18+, vigorous
0
80
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84
With thanks to Cora Craig, CFLRI, Ottawa
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IPAQ
INTERNATIONAL 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?
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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
IPAQ SHORT
IPAQ LONG
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
GPAQ
GPAQ Strengths
+ domains
+ quantifies exposure
+ cross cultural application
GPAQ Weaknesses
+ new measure
+ needs testing
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
Urban design
Density
Access to destinations
Connectivity
Aesthetics
Land use
Green space
Transportation
Infrastructure, Public transit
Safety
Perceptions
Environmental
Determinants
Prevalence environmental determinants and
supports for physical activity, US 1990-1998
50
Percent
40
30
20
10
0
1990
1991
1992
1993
1994
Year
1995
1996
1997
1998
Public Health Physical Activity
Surveillance – Policy-level Data
•Written codes, written standards, unwritten norms
•Legislation (enacted, pending, defeated – level?)
Urban design
Land use
Transportation
Safety
•Organizational policy
Policy
Schools
Worksites
Neighborhood
Physical Activity Policy Research
Framework
Research Type
Outcomes of Policy
Develop and Implement Policy
Determinants of Policy
Identify Policies
Transportation
Parks/Public Spaces
Worksite
School
Sector
Local
Regional
State
National
Level
Prevalence of policy supports for physical
activity, US 1990-1998
50
Percent
40
30
20
10
0
1990
1991
1992
1993
1994
Year
1995
1996
1997
1998
Initial legislative topic areas
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Urban design
Land use
Transportation
Community physical activity
promotion
• Physical education
Upcoming Challenges
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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?
Non-public health
data sources
Media attention
“Critical mass”
Industry and marketing data
individual and aggregate
Trade associations
Others?
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
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
Non-public health
data sources
Environmental
Determinants
Policy
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)?
Difference
Absolute changes between 1969 and 2001
for School Transport – United States
Ham, et al., Unpublished