dose-response relationship
increased levels of exposure are associated with either and increase or decrease risk of the outcome
relative risk
probability of an event (ex. cancer) in exposed group (ex. exercise) compared to probability of the event in not exposed group (ex. no exercise)
what does it mean when the CI crosses the line of no effect
statistically insignificant - no significant association
randomized controlled trials
participants are randomly allocated to receive one or other alternative treatments under study
two types of randomized control trials
- efficacy
- effectiveness
efficacy trials
concerned with what happens when you exercise (internal control)
- under ideal settings
- not changing behaviour
effectiveness trials
concerned with behaviour change (external validity)
- how to get people to sustain exercise
- real-world settings
prospective cohort studies
follows a group of similar individuals over time to see how different factors affect rates of a certain outcome
strengths to prospective cohort study
- large sample
- generalizable
- multiple outcomes can be studied
limitations to prospective cohort study
- expensive
- changes in exposure (PA)
- changes in outcome over time
principle assertion of 24 hour movement guidelines
- composition of movement behaviours are mutually exclusive (co-exist)
- if you change one behaviour you must change another
- provide opportunity to engage in movement behaviours that respect individuality, variability and personal preference
Recommendation 1: MVPA
- 150 min per week
- No longer needs to be in greater than 10 min bouts
- Muscle strengthening activity at least twice a week
- PA that challenges balance for 65+
- reallocate more time into MVPA from other movements
MVPA and All-Cause Mortality
- intensity doesn’t matter (any MVPA counts)
- no lower threshold for benefit (any reduces risks)
- when going from none to little MVPA there is the greatest decline in risk (steep inverse dose response relationship)
- no evidence of risk at high dose exercise
hazard ratio
measure of how often an event happens in one group compared to another (estimates relative risk)
why doesn’t intensity matter in the guidelines?
- There is no evidence of an upper threshold effect (the harder you work doesnt determine your hazard ratio of mortality)
- Guidelines are based on outcomes (ex. mortality), not risk factors,
Recommendation 2: LPA
- Associated with a reduction in risk in a dose-respone manner
- Any amount of LPA counts
- Reallocating sedentary time into LPA is associated with benefit
- LPA is feasible and doesn’t require much time and commitment
Recommendation 3: Sedentary Time
- High sedentary behaviour is associated with negative health outcomes
- There is a positive dose-response relationship btwn sedentary time and mortality
- Reallocating sedentary time into any of the other movement behaviours is associated with benefit
Public Health implications of guidelines
- Promoting participation of MVPA of any length provides more options and increases engagement
- Promotes engagement in exercise of less than 10 min bouts
- LPA encourage participation in routine activities, feasible, supports public health initiatives (stairs, walking, standing)
- Limiting sedentary time will reduce the risk of chronic disease, mortality
dose response relationship between MVPA and health outcomes
- MVPA is associated w substantial reduction in health risk
- Any amount counts
- Reallocate time into MVPA
**MVPA benefits health regardless of sedentary behaviours and LPA
Canada vs. US
Canada: minutes
US: METs (EE)
dose response relationship between LPA and health outcomes
- LPA is associated with a substantial reduction in health risk is dose response manner
- Any amount of LPA counts
- Reallocating some sedentary time into any of the movement behaviours is associated w benefit
approaches for integrating movement behaviours
- Examine effects of one intensity of movement within levels of another (ex. more PA=more you reduce the effect that sedentary has on health)
- Independent effects of two movement behaviours (ex. direct effects of sedentary independent of MVPA)
- Compositional data analysis (CoDA)- “cocktail”
CRF - 3 points
- CRF reduces your risk of mortality, independent of risk factors (ex. metabolic syndrome)
- CRF can be measured pragmatically in clinical settings (step test, treadmill test, non-exercise method)
- CRF can be improved by performing PA and following guidelines (intensity matters)
estimating CRF
- online calculator that estimates fitness using known determinants (sex, weight, age)
- is associated with measures CRF
