W4 - Measurement of Physical Activity Flashcards
What elements of PA do we measure?
- PA type
- PA frequency
- PA Duration
- PA Intensity
What are the objective & subjective methods of measurements?
Objective methods
- directly assess one or more dimensions of physical activity (e.g., frequency, intensity, time, type)
- Capture a variety of metrics e.g.: number of steps, minutes of activity, intensity of activity, and bouts of activity
- Assessment through accelerometery by a direct measure of body movement (acceleration).
▪ When a person moves, the body is accelerated in relation to the muscular forces responsible for the acceleration of the body, and in theory to energy expenditure (EE).
Subjective measurement
- how we measure what people say.
- Rely on recall of activities they participated in/perception of the intensity of the session.
What are pedometers?
▪ Invention ascribed to Leonardo da Vinci (1452-1519)
▪ Develop for the military – make accurate maps of contested territory
▪ Reintroduction traced back to watchmaker Abraham-Louis Perrelet (1729-1826)
▪ Watch rewound itself from the impulses of 15 minutes brisk walking - encouraged people to walk more, to keep the time correct on the watch
What are accelerometers?
What do they do?
Why do we have to alter our epochs based on out research participants?
▪ Accelerometers are movement monitors.
▪ attached to a person’s waist, thigh, wrist, ankle, or shoe.
▪ These motion sensors register accelerations and decelerations of the body and, providing objective and direct measure of the frequency and intensity of movements during physical activity.
▪ count of movement provides a summary measure of the frequency and intensity of movement (i.e., acceleration) over a user-defined time interval called an epoch (e.g., 1m, 30s, 15s, 5s, 1s, etc.)
○ Adults - typically 1 min
○ Children - typically 15 s –> more sporadic, big random bursts of energy
▪ Shorter epochs(given amount of time) provide greater detail but require greater amounts of memory to store the data and reduce the battery life
▪ Count data are time stamped
▪ Counts tell you about FIT but not the 2nd T (type or mode)
Why do we measure PA through accelerometery?
○ Large-scale observational cohort studies
○ controlled trials to examine intervention or treatment efficacy
○ Describing temporal patterns of the intensity of physical throughout the day
○ used as a measure to compare with self-report data. Now it is cheaper they have increasingly been used in large studies
What does an accelerometer do?
Where are the various places accelerometers can be worn?
- Accelerometers are instruments which measure acceleration, the change in velocity of an object over time.
- linear relationship between body acceleration and energy expenditure of that activity
can be worn on:
Wrist - higher PA, more comfortable, more compliance
Thigh - more associated with sedentary behaviour measurement
Waist - more accurate representation
What are the advantages of reactivity accelerometers?
Low burden
Inexpensive
Does not rely on recall
Provides time stamped, continuous PA data (specific)
What are the disadvantages of reactivity accelerometers?
Can’t assess EE related to more stationary activities e.g.: cycling
May be influenced by reactivity
Can’t account for the excess EE related to incline, load bearing
Can have compliance issues
Describe the self-report method of questionnaires
What criteria can differ in questionnaires?
▪ Goals of estimating energy expenditure (EE) in specific types of PA
▪ Questionnaires differ on:
– Time period (past day, week, month, year or lifetime)
– Type of activity (leisure, household, transportation, school/occupation)
– Length (of the questionnaire)
– Administration mode (interviewer, self-administered)
– Outcome measurement (kilocalories, MET-hours, unitless score)
Describe PA questionnaires
(e.g. GPAQ):
– Puts population into categories of physical activity exposure and compare disease incidence between categories
– A clinical setting as a screening tool
▪ Short (5-15) item instruments (e.g. Short-form IPAQ, GPAQ):
– Descriptive epidemiology
– Surveillance of adherence to guidelines on moderate-to-vigorous physical activity
▪ Detailed (15 – 60) item instruments (e.g. Recent PAQ, Long-form IPAQ)
– Quantify patterns
– Examine dose-response associations with health outcomes
– Capture more detailed information about the type, context and intensity of physical activity
What are the advantages of PA questionnaires?
Gains varied info (type, context)
Inexpensive
Easy to reduce the data
What are the disadvantages of PA questionnaires?
Social desirability bias
Inaccuracies in recall
Quality of completion (reading ability)
Limited ability to collect info on
incidental activity
