lecture 4 Flashcards
Avoid —– thinking!!! Avoid just thinking in terms of cause an effect
Think about all the elements and complex interactions of factors that come into play.
reductionist
Feedback loops (2)
- Negative= Homeostasis
- Positive= increases and keeps increasing (ex. People running causes packing which causes people to run more)
Complex problems cannot use —— in their solutions.
Simple problems can.
reductionist thinking
Iceberg image:
- Our mental model and mental understanding of the problems drives the “visible” events, patterns, and trends
- To change the problem, we must change our mental models. This is difficult to do but very effective.
Measuring physical activity: is it a good test?
- Validity= can we compare to a gold standard?
- Accuracy= how close is measured value to true value
- Reliability= repeatable? Interreliable, intrrareliabile?
- Sensitivity= can you detect a small change
MET
=1 metabolic equivalent (3.5 ml/kg/min)
Approx. equal to energy consumption at rest
Measured from amount of O2 consumption
Most common measured of PA
= self-reports
- Recall activity done retrospective
- Or proactively: w a diary
Child self-reports are common too (done by the parents)
- Higher chance of inaccuracy!!!
We want sample to be representative so use
stratified random samples
3 types of internet samples
- Unrestricted: poor representation due to self-selection
- Screened: “stratifies” your sample
‘panel house’= respondents who fill out a preliminary questionnaire that classifies them into segments - Recruited: recruit ppl by phone or email and send a survey
IPAQ
- Self-administered questionnaire
- Identifies how much PA someone has done
- Most common/widely used questionnaire
- Retrospective self-report
- Add up minutes in each category
limitations: population level, not individual level, “cut points”, tend to overestimate PA,
HR monitors
- ECG= gold standard
- Depends on hydration, hormones, medication, caffeine, not accurate at low intensity levels
Pedometers
- Counts steps
- 10k steps not supported by the literature
Accelerometers
-volume and intensity
- cant swim or cycle with it
- what is the algorithm based on: 20 yr old male??
gold standard measurement of energy expenditure
doubly labeled water!!!
- “gold standard”, v high validity
- ingest an isotope of 2H and 18O
- 1 to 3 weeks later energy for the time period can be calculated
Indirect calorimetry
- measurement of O2 consumption during PA
3 types of self reports
- self-administered recall
- interview-administered recall
- diary
self-reports of PA limitations
Bias, memory, confusion between “vigorous and moderate”
a good self-report will be
Valid
Reliable
Sensitive to change
Will not influence respondents behaviour
Reasonable, administration cost
smaller target group, larger
proportion of ppl have to be in the sample
advantages of internet surveys
fast
data is electronic
cheap
quickly modify survey if needed
anonymity–> more accurate responses
can do survey from anywhere
disadvantages of internet surveys
not good for open-ended qs
hard to reach challenging populations
survey fatigue
hard to verify identity
timing is important
anonymity–> less accurate responses
how to increase response rates of surveys?
pre-notification
reminders
co-operate w organization
interesting qs
short questionnaire
reward for participating
IPAQ “high”
3000 total MET min/week
IPAQ “moderate” minimally active
600 MET min/week
