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Validity and reliability of the Fitbit Zip as a measure of preschool children's step count
Catherine A Sharp1, Kelly A Mackintosh2, Mihela Erjavec1
1School of Psychology, Bangor University, Bangor, Gwynedd, UK.
Insights
Fitbit Zip accelerometers accurately measure preschool children's steps in childcare settings. This study confirms their reliability and validity for physical activity research in young children.
Area of Science:
- Pediatric physical activity measurement
- Wearable technology validation
- Childhood obesity research
Background:
- Accurate physical activity measurement is crucial for understanding preschool children's health.
- Existing research has not prioritized validating tools for this age group.
- Consumer-grade accelerometers like Fitbit Zip offer potential for large-scale studies.
Purpose of the Study:
- To evaluate the inter-rater reliability of observer step counts.
- To assess the inter-device reliability of Fitbit Zip accelerometers.
- To determine the validity of Fitbit Zip accelerometers for measuring step counts in preschool children.
Main Methods:
- Fifty-six 3-4-year-olds wore two Fitbit Zip accelerometers in childcare settings.
- Children performed a timed walking task, recorded via video.
- Two observers independently counted steps; data analyzed using ICC, CCC, and Bland-Altman plots.
Main Results:
- Excellent inter-rater reliability for observer step counts (ICC=1.00).
- High inter-device reliability for Fitbit Zips (ICC=0.91) and good concordance with observer counts (r=0.77).
- Acceptable absolute percentage error (6%-7%) with some bias identified in Bland-Altman analyses.
Conclusions:
- Fitbit Zip accelerometers demonstrate good reliability and validity for measuring step counts in preschool children.
- These devices are suitable for use in childcare settings for physical activity assessment.
- Findings support the use of Fitbit Zip for research on physical activity and health in young children.
Objectives:
Validation of physical activity measurement tools is essential to determine the relationship between physical activity and health in preschool children, but research to date has not focused on this priority. The aims of this study were to ascertain inter-rater reliability of observer step count, and interdevice reliability and validity of Fitbit Zip accelerometer step counts in preschool children.
Methods:
Fifty-six children aged 3-4 years (29 girls) recruited from 10 nurseries in North Wales, UK, wore two Fitbit Zip accelerometers while performing a timed walking task in their childcare settings. Accelerometers were worn in secure pockets inside a custom-made tabard. Video recordings enabled two observers to independently code the number of steps performed in 3 min by each child during the walking task. Intraclass correlations (ICCs), concordance correlation coefficients, Bland-Altman plots and absolute per cent error were calculated to assess the reliability and validity of the consumer-grade device.
Results:
An excellent ICC was found between the two observer codings (ICC=1.00) and the two Fitbit Zips (ICC=0.91). Concordance between the Fitbit Zips and observer counts was also high (r=0.77), with an acceptable absolute per cent error (6%-7%). Bland-Altman analyses identified a bias for Fitbit 1 of 22.8±19.1 steps with limits of agreement between -14.7 and 60.2 steps, and a bias for Fitbit 2 of 25.2±23.2 steps with limits of agreement between -20.2 and 70.5 steps.
Conclusions:
Fitbit Zip accelerometers are a reliable and valid method of recording preschool children's step count in a childcare setting.
