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Intra-individual variation in children's physical activity patterns: Implications for measurement
Kate Ridley1, Tim Olds, Beth Hands
1Flinders University, Australia. Kate.Ridley@flinders.edu.au
Insights
Children's daily physical activity (PA) varies significantly, impacting measurement accuracy. Sampling more days reduces error, but fewer days may suffice depending on research needs.
Area of Science:
- Pediatric Exercise Science
- Behavioral Epidemiology
- Biostatistics
Background:
- Children exhibit considerable day-to-day variability in physical activity (PA) and sedentary behaviors.
- This intra-individual variability poses challenges for precise measurement of PA and sedentary behavior variables.
- Understanding and mitigating random error is crucial for accurate assessment in pediatric populations.
Purpose of the Study:
- To explore strategies for reducing random error in PA and sedentary behavior assessment due to intra-individual variability.
- To demonstrate the impact of varying sampling durations on the precision of PA and sedentary behavior estimates in adolescents.
- To guide researchers in determining optimal sample sizes and durations for assessing children's PA patterns.
Main Methods:
- Utilized self-reported data from 298 adolescents aged 13-14 years.
- Compared PA and sedentary behavior estimates derived from 1 to 7 days of recall data.
- Calculated intra-individual coefficients of variation for key variables including PA level, moderate-to-vigorous physical activity (MVPA), screen time, and sleep.
Main Results:
- Large intra-individual coefficients of variation were observed: PA level (14.5%), MVPA (83.4%), screen time (60.8%), and sleep (12.2%).
- Measurement error decreased as the number of sampled days increased.
- The precision of estimates varied based on the specific PA or sedentary behavior variable being assessed.
Conclusions:
- While increased sampling days enhance precision, shorter sampling periods may be adequate for certain research questions.
- Researchers must conduct power analyses considering inter- and intra-individual variability to determine appropriate sampling durations.
- Optimizing sampling strategies is essential for reliable assessment of children's physical activity and sedentary behavior patterns.
Abstract:
Children's physical activity (PA) patterns change from day to day. This intra-individual variability affects precision when measuring key physical activity and sedentary behaviour variables. This paper discusses strategies used to reduce the random error associated with intra-individual variability and demonstrates the implications for assessing PA when varying number of days are sampled. Self-reported data collected on two hundred and ninety eight 13-14-year-olds were used to compare estimates of PA and sedentary behaviour derived from between 1 and 7 days of recall data. Large intra-individual coefficients of variation were calculated for physical activity level (14.5%), moderate-to-vigorous physical activity (83.4%), screen time (60.8%) and sleep (12.2%). While the magnitude of error associated with estimating means decreased as more days were sampled, the paper notes that depending on the nature of the research question being asked, sampling fewer days may yield sufficiently precise estimates. Therefore, researchers should conduct power analyses based on estimated inter- and intra-individual variability and sample size to determine how many days to sample when assessing children's PA patterns.
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