physical activity assessment techniques validity, reliability, tools
TRANSCRIPT
Physical Activity Assessment Techniques
Validity, Reliability, Tools
Introduction
http://abcnews.go.com/WNT/video/america-lags-walking-exercise-obesity-weight-11808653
Where are we?
You should be familiar with the PA guidelines and the ways PA can be quantified
The purpose of this lecture is to help you understand and identify multiple methods to quantify PA so that you can determine if your client meets the guidelines (and prescribe PA)
We must determine what makes one assessment technique “better” than another
Measurement Issues
How can one monitor be “better” than another?
Consider: Sensitivity to change (precision) Reactivity Comfort to respondent (feasibility) Cost of administration (feasibility)
The above can be considered your preference
Two considerations are far more important – validity and reliability
Validity + Reliability
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Reliable w/
poor ValidityPoor
Valid + Reliable
Statistical Note
Reliability and Validity are generally expressed as correlation coefficients Range from -1 to +1
Stronger (and better) relationships are seen closer to 1
A correlation of 0.00 basically means there is no relationship (poor reliability, poor validity)
Recap of Measurement Issues
Evaluate each measurement tool based on these concepts Sensitivity to change (precision) Reactivity Comfort to respondent (feasibility) Cost of administration (feasibility) Validity (accuracy) Reliability (consistency)
Physical Activity Assessment Tools:
Figuring Out Energy Expenditure and Minutes of
Activity
Activity Monitoring Tools
Currently, there is a strong relationship between the feasibility of a PA assessment tool and it’s validity – and that relationship is in the wrong direction
We’ll tackle these different methods in order of weakest validity to strongest
Keep in mind that the tool you select is based on what you want to know and how you are going to use it!!
ValidityValidity
Fea
sib
ility
Fea
sib
ility
QuestionnaireQuestionnaireDiaryDiary
PedometersPedometers
HR monitorsHR monitors
AccelerometersAccelerometers
Direct observationDirect observation
DLWDLW
I. calorimeteryI. calorimetery
Physical Activity Assessments (Feasibility-Validity)
Self Report Tools
Subjective assessment tools are at the mercy of those providing the information Self-Report Instruments
Recall Diaries/Logs Questionnaire
These tools require the client identify their own PA levels (to some degree)
Use time and intensity of PA to further extrapolate to EE
Recall
Example: 7-Day PAR (Physical Activity Recall)
One week period, interview based, participant recalls: Sleep Moderate (minutes) Hard (minutes) Very Hard (minutes) Minutes working on strength/flexibility
Note: Interviewer script, memory cues
Diary/Log
Instead of having the subject recall activity, perhaps validity/reliability can be improved by having them keep constant measurement?
Bouchard 3-Day Physical Activity Diary Minutes of PA and EE
Note: Short intervals, MET-reference guide
Questionnaire
Questionnaires do not ask clients to recall a specific time, nor do they use a continuous log
Simply ask the client how active they are normally
Some are more detailed than others
Example: Godin Leisure-Time PA Questionnaire
Other Self-Report Instruments Numerous examples:
ACLS Questionnaire Paffenbarger Physical Activity Recall CARDIA Physical Activity History Modifiable Physical Activity Questionnaire Yale Physical Activity Survey Historical Physical Activity Questionnaire NHANES Etc…
Other Self-Report Instruments Numerous examples:
ACLS Questionnaire Paffenbarger Physical Activity Recall CARDIA Physical Activity History Modifiable Physical Activity Questionnaire Yale Physical Activity Survey Historical Physical Activity Questionnaire NHANES Etc…
No Caption Available.
Other Self-Report Instruments Numerous examples:
ACLS Questionnaire Paffenbarger Physical Activity Recall CARDIA Physical Activity History Modifiable Physical Activity Questionnaire Yale Physical Activity Survey Historical Physical Activity Questionnaire NHANES Etc…
NHANES
For NHANES, participants are asked very specific questions on about 10 physical activities (like walking, cycling, aerobics, playing sports, etc…)
“On how many of the previous 30 days did you participate in ________?”
“On average, when you participated in _______, how long did you do this activity?”
Remember this?
Data show that nearly four in ten (38.3 percent) adults reported no participation in leisure-time physical activity.
Does knowing how PA was assessed change your perspective on inactivity in the US?
Self-Report: Validity and Reliability In general, reliability of self-report
measures are low-moderate Low to non-existent reliability for light activity High reliability for vigorous activity
In general, validity of self-report measures are moderate for energy expenditure and low for minutes of physical activity Godin ~ 0.30-0.40 compared with kcal/day
Self-Report
Strengths: Low time, cost, work commitment (feasible) When used with MET-compendium, both
energy expenditure and minutes of activity can be identified
Can identify time-frame easily (past month, year, lifetime, etc…)
Allows determination of the “dimensions” of physical activity with both qualitative and quantitative information
Self-Report
Limitations: Biased towards structured, high intensity
(exercise) Low-moderate validity and reliability Not good for estimating minutes of PA (alright
at total EE) Participant ignorance (what’s moderate again?) Certain groups may have poor recall ability
(children) Potential content validity problems
(participants may misinterpret questions) Social desirability
Physical Activity Assessment Techniques
Gadgets
ValidityValidity
Fea
sib
ility
Fea
sib
ility
QuestionnaireQuestionnaireDiaryDiary
PedometersPedometers
HR monitorsHR monitors
AccelerometersAccelerometers
Direct observationDirect observation
DLWDLW
I. calorimeteryI. calorimetery
Physical Activity Assessments (Feasibility-Validity)
Pedometers
Simple pedometers are the first objective monitoring tool we will discuss
Provide information on ambulatory physical activity, priced between $20-$300
Walking: Is the #1 ranked physical activity in the US Accounts for a major portion of total daily
activity Confers substantial health benefits
Simple Question
How valid do you think a pedometer is? High validity in measuring steps, but… Moderate validity in measuring physical
activity (0.30-0.50)
Pedometers assess steps/day, not minutes of activity, or intensity, or energy expenditure Construct Validity with minutes/EE Raw Volume of PA
Pedometers
Although this is a limitation, pedometers are good at what they are supposed to do
Due to their cost and simplicity, they are widely studied and used
We even have separate recommendations for pedometers – and you all probably know it!
Target Steps/day
Hanato (1997), in a Japanese sample, found that subjects getting 10,000 steps/day were more likely to have lower blood pressure and %BF
This “10,000” was pulled from thin air Nice round number, easily remembered, easily
interpretable to clients (not like METs or “moderate” activity
In Japan, the term for pedometer is manpo-kei, which is literally translated to “10,000 step meter”
Versus the 30 minutes (old rec) Welk et al. found that 73% of subjects that
averaged >10,000 steps/day performed >30 minutes of moderate activity
This is due to a moderate construct validity between steps/day and minutes of activity
Overall, it appears that getting about 10,000 is somewhere close to the recommended amount of PA
Pedometer-Specific Groups
Pedometers alone can be used to categorize clients into physical activity groups:
Sedentary: <5000 steps/day Low Active: 5000-7499 steps/day Somewhat Active: 7500-9,999 steps/day Active: 10,000-12,499 steps/day Highly Active: 12,500 steps/day
These targets can be used to motivate clients outside of the gym
Old-Order Amish
In 2004, Bassett completed a study analyzing the steps/day (physical activity) of an old-order Amish community
Besides shaming typical US Adults, it demonstrates what physical activity levels may have looked like 150 years ago Keep in mind that ~ 10,000 steps indicates
they meet US PA guidelines and 12,500 steps is Highly Active
Self-Report
US Adult Guidelines: Minimum 150 min. of moderate activity or 75 min. vigorous
Amish Men: 0% Obesity, Women: 9% Obesity
Pedometer
Strengths: Objective Inexpensive and easy to use Moderate Validity Interpretable Specific targets exist for prescription
Limitations: Doesn’t capture all PA Not direct minutes of PA or EE Reactivity?
ValidityValidity
Fea
sib
ility
Fea
sib
ility
QuestionnaireQuestionnaireDiaryDiary
PedometersPedometers
HR monitorsHR monitors
AccelerometersAccelerometers
Direct observationDirect observation
DLWDLW
I. calorimeteryI. calorimetery
Physical Activity Assessments (Feasibility-Validity)
Accelerometer
Due to the lack of “other” activities being captured by the pedometer, accelerometers have been created
Walking and running 20 steps are equally weighted in pedometry Accelerometers can tell the difference
Instrumentation / Principles Detection of acceleration:
Piezo-electric bender element is sensitive to acceleration - transducer bends and a proportionate electrical charge created
Amount of movement is summed over time
Movement is reported in counts/time
Real time recording allow temporal patterns to be observed
Data Output Whole-Day Accelerometry Adult
0
1000
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90001
2:0
0 A
M
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M
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:00
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1:0
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M
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:00
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Mo
ve
me
nt
Co
un
ts
Sleep
Walk Walk
TVLunch
Off
Outcome Measures Average movement count (total activity)
Counts/min Equations to predict EE from movement counts
Kcal/min or METS Time spent being active
Number of minutes above threshold (cut point derived from regression equation)
Number of bouts of activity Number of times with continuous movement
greater than threshold Ie – were they active for 10 continuous minutes?
Measurement Issues Accelerometry Validity
Indirect calorimetry lab r = 0.80 to 0.90 lab Indirect calorimetry field r = 0.40 to 0.60
Reliability Inter-instrument reliability consistently high (r > 0.90)
Sensitive to change Non-reactive Acceptable to subject Acceptable cost? (units $200 to 500, interface $500)
Development of Prediction Equations and Activity “Cutpoints”
Act
ivit
y co
unts
VO2 or energy expenditure
Light
Moderate
Vigorous
Characterize relationship between movement counts oxygen consumption
0
1000
2000
3000
4000
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6000
7000
8000
9000
12:0
0 AM
1:00
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0 PM
TIME
Mov
emen
t Cou
nts
Movement Count Cut-Point
Application of Count Thresholds for Processing Accelerometer Data
If a threshold accurately defines a particular level of activity, the time spent in activity can be determined.
NHANES
Recall that about 40% of US adults report no leisure-time activity Based on what assessment of PA…?
NHANES recently introduced accelerometry into their survey Objective assessment of PA How many people “meet” guidelines?
Males, Moderate and Vigorous Activity x Age Group
Remember: This is the MEAN or average minutes
Females, Moderate and Vigorous Activity x Age Group
Remember: This is the MEAN or average minutes
How does that compare?
Approximately 5-10% of Americans meet or exceed the recommendation of 30 minutes of at least moderate activity on 5-7 days of the week
Objective vs Subjective methods of assessment
Limitations:
Accelerometers, while very good at what they do, are not without limitations: Not sensitive some movements Not sensitive to grade Not sensitive to increased weight Restricted to mainly ambulatory activity
ValidityValidity
Fea
sib
ility
Fea
sib
ility
QuestionnaireQuestionnaireDiaryDiary
PedometersPedometers
HR monitorsHR monitors
AccelerometersAccelerometers
Direct observationDirect observation
DLWDLW
I. calorimeteryI. calorimetery
Physical Activity Assessments (Feasibility-Validity)
Gold Standard Methods
If you really need to know energy expenditure – then doubly labeled water is THE best way to do it
Metabolism boils down to O2 consumption and CO2 production If I know how much oxygen you use and carbon
dioxide you produce, then I know how many calories you burn (not an estimate)
How can we keep track of O2 and CO2?
Few options
1) Metabolic Analyzers (Indirect calorimetery) Lab-based Portable units
Capable of TEF + PAEE + RMR
Few options
2) Metabolic Chamber Pennington Biomedical Research Unit:
Few Options
Even portable metabolic analyzers are restrictive – not applicable for long-term energy expenditure
Doubly labeled water combines with metabolic analyzer estimates of RMR and TEF to determine PAEE over the course of multiple days with no restrictions
Few Options
3) Doubly Labeled Water Free living estimates
Drink known amount of two stable isotopes (deuterium and oxygen-18)
Collect urine on “drink day” and “end day” to determine the quantity of the isotopes used in metabolism (CO2 production)
Subtract RMR and TEF = PAEE
Doubly Labeled Water
Precise kcal estimates
Can be used from 3 days to 2 weeks
Lacks estimates of minutes of PA or any other qualitative information
Cost ~ $800 per person, per measurement period (depends on size)
Difficult to analyze (and that costs more money)
New Technologies
Validity
Feasib
ilit
yFeasib
ilit
y
DLWDLW
DiarieDiariess Self-reportsSelf-reports
PedometersPedometers
HR HR monitorsmonitorsAccelerometerAccelerometer
ssDirect Direct observationobservation
I. I. CalorimetryCalorimetry
Pattern Pattern Recognition Recognition MonitorsMonitors
Gadgets
Pattern Recognition Monitors Combine multiple PA assessment methods –
plus a few new ones High Validity Cost $80-$5000 Combine the strengths of the previous
methods and advanced equations to accurately assess: What you do When you do it How intense
Energy Expenditure and Minutes of Activity
Gadgets
Kam Monitor Cost ~ $80
Pedometer + Accelerometer
Output ~ METs (Kam Points)
www.mykamunity.com
It’s like Facebook, but for physical activity
Corporate Wellness, School-Health
Gadgets
Actiheart A single-unit instrument that uses
accelerometry in combination with electrocardiogram (ECG) signals to determine respiration, movement, and intensity. HR monitor + Accelerometer
Respironics/Mini Mitter, Bend, OR – www.minimitter.com
Actiheart monitor
• $750 per/unit.$750 per/unit.
•60s epochs for up to 11 60s epochs for up to 11 continuous days.continuous days.
• Combines activity Combines activity monitor and heart rate monitor and heart rate monitor. monitor.
• Branch chain algorithms Branch chain algorithms used to estimate EE.used to estimate EE.
Actiheart Output / Report
Gadgets
IDEEA Monitor Intelligent Device for Energy Expenditure
Activity
Places 5 accelerometers in 5 locations on body
Wires connect sensors and feed into a small computer
A light (59-grams) data
collection microcomputer.
Five sets of sensors:
Chest Thighs Soles of the feet (2).
It can measure angles of body segments and
movement (acceleration) in 2 directions.
IDEEA- Characteristics
IDEEA- Output Data
IDEEA Reports- Detailed gait
profiles
IDEEA
Extremely invasive
Cost ~ $4000-$5000
Extremely valid/reliable
Gadgets
SenseWear Pro Armband (research grade) GoWearFit BodyBugg
www.bodymedia.com
Non-invasive armband that combines temperature readings with pedometer and accelerometer type monitoring
SenseWear Mini Armband (Mini)
SenseWear Pro Armband
Low MotionLow Motion High MotionHigh Motion
High Heat FluxHigh Heat Flux
Low Heat FluxLow Heat Flux
ALGORITHMALGORITHM
ALGORITHMALGORITHM
ALGORITHMALGORITHM
SWA output
Biking Heat FluxHeat FluxEnergy Expenditure
SWA output
SWA output
Energy ExpenditureHeat FluxAcceleration
Sensewear Reports
Gadgets
Sensewear ~ $250$1900 software
BodyBugg or GoWearFit ~ $150-300 $85 yearly payment (online software)
Calabro and Welk
30 people wore two armband monitors for 2 weeks.
No significant differences in TEE.
More recent versions within 20 kcal of DLW
Minifly SWA DLW1500
1700
1900
2100
2300
2500
2700
2900
3100
3300
3500
Dai
ly e
nerg
y ex
pend
iture
(kca
l/day
)
Summary
Multiple methods exist to determine the various quantities of physical activity
As most clients are concerned with diet, PA, and weight management, these are certainly useful tools
Keep in mind strengths and limitations of each method – what are they good at? Not so good?