Physical Activity Assessment Techniques Validity, Reliability, Tools.

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

+++++++

+ ++++

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

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…

No Caption Available.

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

DLWDLW

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

DLWDLW

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

Walk Walk

TVLunch

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”

VO2 or energy expenditure

Moderate

Vigorous

Characterize relationship between movement counts oxygen consumption

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

DLWDLW

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

yFeasib

DLWDLW

DiarieDiariess Self-reportsSelf-reports

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

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

SWA output

Biking Heat FluxHeat FluxEnergy Expenditure

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

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?

Physical Activity Assessment Techniques Validity, Reliability, Tools.

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