Related Experiment Video
Updated: May 7, 2026
Physical Activity Measurement in Children Accepting Table Tennis Training
Published on: July 27, 2022
Assessing preschool children's physical activity: how many days of accelerometry measurement
Cheryl L Addy1, Jennifer L Trilk, Marsha Dowda
1Dept. of Epidemiology and Biostatistics, Arnold School of Public Health, University of South Carolina, Columbia, SC.
Insights
Determining physical activity in young children requires careful consideration of accelerometry duration. This study suggests that while seven days are ideal, fewer days can yield reliable estimates for moderate-to-vigorous physical activity (MVPA) and total physical activity (PA) in preschoolers.
Area of Science:
- Pediatric Exercise Science
- Biomedical Engineering
- Public Health Nutrition
Background:
- Accurate measurement of physical activity (PA) in preschool-aged children is crucial for understanding health behaviors.
- Accelerometry is a common objective method, but optimal wear time for reliable data in this age group is not well-established.
Purpose of the Study:
- To determine the minimum number of days of accelerometry needed for accurate estimation of moderate-to-vigorous physical activity (MVPA) and total PA in 3- to 5-year-old children.
- To assess reliability across different measurement periods: all days, weekdays, and in-school activities.
Main Methods:
- 204 children aged 3-5 years from 22 preschools participated.
- Participants wore accelerometers for at least 6 hours/day for up to 12 days.
- Intraclass correlation coefficients (ICCs) were used to estimate the number of days for reliable PA and MVPA measurement.
Main Results:
- High ICCs were observed for all metrics, indicating good reliability.
- Reliability estimates ranged from 0.78 (total PA-all days) to 0.84 (in-school total PA).
- The Spearman-Brown prophecy suggested 3-4 days for weekday measures and 5-6 days for all-day measures to achieve acceptable reliability.
Conclusions:
- A full seven days of accelerometry is recommended for optimal PA and MVPA assessment in preschoolers.
- Researchers can achieve acceptable reliability with shorter measurement periods (3-6 days) depending on the specific metric and desired precision.
- These findings provide practical guidance for optimizing accelerometry protocols in early childhood PA research.
Abstract:
The purpose of this study was to determine the minimum number of days of accelerometry required to estimate accurately MVPA and total PA in 3- to 5-year-old children. The study examined these metrics for all days, weekdays, and in-school activities. Study participants were 204 children attending 22 preschools who wore accelerometers for at least 6 hr per day for up to 12 days during most waking hours. The primary analysis considered the intraclass correlation coefficient (ICC) for each metric to estimate the number of days required to attain a specified reliability. The ICC estimates are 0.81 for MVPA-all days, 0.78 for total PA-all days, 0.83 for MVPA weekdays, 0.80 for total PA-weekdays, 0.81 for in-school MVPA, and 0.84 for in-school total PA. We recommend a full seven days of measurement whenever possible, but researchers can achieve acceptable reliability with fewer days, as indicated by the Spearman-Brown prophecy: 3-4 days for any weekday measure and 5-6 days for the all-days measures.
