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Validity and comparability of a wrist-worn accelerometer in children
Orjan Ekblom1, Gisela Nyberg, Elin Ekblom Bak
1Åstrand Laboratory of Work Physiology, The Swedish School of Sport and Health Sciences, Stockholm, Sweden.
Journal of Physical Activity & Health
|March 29, 2012
Summary
The wrist-worn Actiwatch is a valid and reliable tool for measuring children's physical activity and energy expenditure. It provides accurate estimates for light, moderate, and vigorous activities, making it a practical option for long-term monitoring.
Area of Science:
- Pediatric physical activity monitoring
- Biomedical engineering
- Exercise physiology
Background:
- Wrist-worn accelerometers offer a more convenient alternative to hip-worn devices for physical activity assessment.
- Ease of wear may improve long-term adherence to physical activity monitoring.
Purpose of the Study:
- Assess the validity of the Actiwatch (wrist-worn) for estimating energy expenditure.
- Determine cut-off values for classifying activity intensities (light, moderate, vigorous).
- Compare Actiwatch data with a hip-worn Actigraph and evaluate Actiwatch reliability.
Main Methods:
- Indirect calorimetry served as the criterion measure for validity assessment.
- Receiver Operating Characteristic (ROC) analyses were used to establish activity intensity cut-off values.
- Simultaneous wear of Actiwatch and Actigraph during free-living conditions assessed comparability; reliability was tested using a mechanical shaker.
Main Results:
- A strong overall correlation (0.80) was observed between accelerometer output and energy expenditure (P < .001).
- ROC analysis identified cut-off values of 80, 262, and 406 counts per 15 s for 1.5, 3, and 6 METs, respectively.
- Energy expenditure estimates showed significant differences between Actiwatch and Actigraph (P < .05), with Actiwatch exhibiting low intra- and inter-instrument variation (0.72%–8.4%).
Conclusions:
- The wrist-worn Actiwatch demonstrates validity and reliability for estimating energy expenditure and physical activity intensity.
- Established cut-off values enable accurate classification of activity levels in children aged 8 to 10 years.
- The Actiwatch is a suitable tool for pediatric research and clinical applications requiring objective physical activity measurement.
