Validation and calibration of the activPAL™ for estimating METs and physical activity in 4-6 year olds
Objectives Examine the predictive validity of the activPAL™ metabolic equivalents equation, develop an activPAL™ threshold value to define moderate-to vigorous-intensity physical activities, and examine the classification accuracy of the developed moderate-to vigorous-intensity physical activities threshold value in 4- to 6-year-old children. Design A sample of forty 4- to 6-year-old children from the Illawarra region in New South Wales, Australia were included in data analysis. Methods Participants completed a ∼150-min room calorimeter protocol involving age-appropriate sedentary behaviors, light-intensity physical activities and moderate-to vigorous-intensity physical activities. activPAL™ accelerometer counts were collected over 15 s epochs. Energy expenditure measured by room calorimetry and direct observation were used as the criterion measure. Predicted metabolic equivalents were calculated using the activPAL™ metabolic equivalents equation (activPAL™ software version 5.8.0). Predictive validity was evaluated using dependent-samples t-tests. Participants were randomly allocated into two groups to develop and cross-validate an intensity threshold for moderate-to vigorous-intensity physical activities. Receiver operating characteristic curve analysis was used to determine moderate-to vigorous-intensity physical activities threshold. The classification accuracy of the developed threshold was cross-validated using sensitivity, specificity, and area under the receiver operating characteristic-curve. Results The activPAL™ metabolic equivalents equation significantly overestimated metabolic equivalents during sedentary behaviors and significantly underestimated metabolic equivalents for light-intensity physical activities, moderate-to vigorous-intensity physical activities and total metabolic equivalents compared to measured metabolic equivalents (all P < 0.001). The developed threshold of ≥1418 counts per 15 s resulted in good classification accuracy for moderate-to vigorous-intensity physical activities. Conclusion The current activPAL™ metabolic equivalents equation requires further development before it can be used to accurately estimate metabolic equivalents in preschoolers. The developed threshold exhibited acceptable classification accuracy for moderate-to vigorous-intensity physical activities; however studies cross-validating this moderate-to vigorous-intensity physical activities threshold in free-living preschool-aged children are recommended.
Janssen, X., Cliff, D. P., Reilly, J. J., Hinkley, T., Jones, R. A., Batterham, M., Dr Ulf Ekelund, U., Dr Soren Brage, S. & Okely, A. D. (2014). Validation and calibration of the activPAL™ for estimating METs and physical activity in 4-6 year olds. Journal of Science and Medicine in Sport, 17 (6), 602-606.