Lec 2: Measuring PA & Sedentariness Flashcards
Why is it important to Measure PA?
1-4
1 Specify which aspects of PA are important for a particular health outcome
ex: cardio vs strength for depression
2 Prevalence of PA in population
3 Monitor changes in PA over time
4 Monitor effectiveness of interventions
Criteria for Evaluating PA Measures
1-6
1 Validity (accuracy)
- error in self-report
- pedometer can assess hair brushing as steps
2 Reliability (consistency) - test-retest
3 Sensitivity to change - sensitive enough to pick up small changes
4 Being non-reactive - doesn’t influence respondent behaviour
5 Being acceptable to respondent (decrease burden)
6 Acceptable cost of administration (self-report -> pedometer
Motion Sensors: - - - -
PROS & CONS of pedometers:
- Pedometers (Digiwalker) steps/min
- Accelerometers (ActiGraph) change in acceleration - speed
- Worn at different sites
- PA Monitors for consumers
P & C:
P: small, good for many population, decrease burden, easy to collect & analyze, cheaper, VALID/RELIABLE
C: reactivity, *doesn’t assess intensity, freq, duration
Motion Sensors:
Internal Mechanisms
-
I M - traditional pedometer: spring mechanism - when there is force = movement of spring to collect a step
M & D
- simple pedometer = manual reset
- accelerometer -based pedometer = rolling record & # of min
- Research - based accelerometer - increased quality, memory
Direct Outputs =
vs
Indirect Outputs =
From accelerators:
= you as consumer can see
= needs to be processed by company (isn’t rigid difference)
: summarized digital display
classified as volume indicators & rate indicators
Direct Outputs:
Volume Indicators
1
2
Axis
1
2
3
Rate Indicators
1
2
Actigraph cut off points SLIDE 14
1 Steps/day
- accumulated
- or relative to preferred time
2 Total activity counts/day
Single or Tri axis accelerometer: 1 vertical 2 Anterior/Posterior (front / back) 3 Medio-lateral (side to side) **** Look at notes for visual****
1 Cadence or steps/min - relates to intensity - time-stamping capability (4:01 - 4:06) 2 Activity counts/min - not meaningful without reference frame [EPOCHE = time interval] - researcher sets
- 1 2 3
Derived Outputs: (1) Peak Effort
- AKA
- Ex
: (2) Time Indicators 1 Ex 2 Ex : (3) Event Counts Ex
= extra processing needed
- generated by later processing
- classified as (1)peak effort indicators, (2)time indicators and (3)event counts
AKA Peak Cadence
Ex: Peak 30 min cadence
= take avg steps per min
+ take most active steps in 30 min (avg 30 min)
1 Time -stamped STEP accumulation patterns
Ex 40-59 steps = purposeful steps [SLIDE 17]
“How many min a day doing purposeful steps?”
2 Time-stamped ACTIVITY COUNT accumulation patterns
- cut-off points
- refer to actigraph cut-off points [Ex : MOD intensity = 2020-5998 activity counts / min]
- SLIDE 19 visual
(3) Event Counts
Ex # of breaks in sedentary time
(transition btw sed beh & PA of any intensity)
Derived Outputs
- uses:
[Ex from his FitBit data]
EPOCHE interval of 5 min / 15 min
Data Collection Protocol - for researchers Choice of Instrument 1-5 Decision Rules - -
- uses an algorithm
- Energy expenditure - calories
- distance
1 Attachement site (wrist, hip etc)
2 Metric (output) choice
3 Epoch choice (interval) - balance small & large intervals
4 Monitoring frame (# & types of days - holiday/weekend) - avg = 7 days
- reactivity (no display data, seal, familiarization)
5 Calibration (quality control)
D R
- Wear Time (~10 hrs waking time/day)
- Data Transformation
Limitations of Motion Sensors
1-5
1 Most sensitive to ambulatory(walking) movement (not arms - swimming example)
2 Reactivity
3 No contextual information
4 Resources & expertise
5 Difficulty in comparing output data from devices different companies
RESEARCH
Illustration of Accelerometer-measured PA & SB
Nelson et al 2019
SLIDE 29-32
