Evaluation of Actical equations and thresholds to predict physical activity intensity in young children

Area of Science:

• Pediatric Exercise Science
• Biomedical Engineering
• Physical Activity Measurement

Background:

• Accurate measurement of physical activity energy expenditure (AEE) is crucial for understanding energy balance in children.
• Actical devices and their associated equations/cut-points are widely used but their validity in young children requires examination.
• Preschoolers exhibit unique movement patterns that may affect the accuracy of accelerometry-based measures.

Purpose of the Study:

• To evaluate the validity of Actical activity energy expenditure (AEE) equations and intensity cut-points in preschoolers.
• To compare the accuracy of different Actical cut-points and equations against criterion measures.
• To provide recommendations for accurate physical activity intensity classification in preschool children.

Main Methods:

• Forty preschoolers (4-6 years) underwent a ~150-minute room calorimeter protocol.
• Direct observation and Actical accelerometry were used to measure activity energy expenditure (AEE) and physical activity intensity.
• AEE and intensity were calculated using Actical equations and cut-points from Adolph, Evenson, Pfeiffer, and Puyau.
• Statistical analyses included paired sample t-tests and classification accuracy metrics (weighted kappas, sensitivity, specificity, ROC curves).

Main Results:

• The Pfeiffer equation significantly overestimated AEE during sedentary behavior and underestimated it during light-intensity physical activity.
• No significant differences were found between measured and predicted AEE during moderate-to-vigorous intensity physical activity (MVPA) using the Pfeiffer equation.
• The Adolph cut-point demonstrated superior accuracy in classifying sedentary behavior, light-intensity physical activity, and MVPA compared to other tested cut-points.
• Overall, Actical equations did not accurately estimate AEE across all intensity levels in preschoolers.

Conclusions:

• Current Actical equations lack precision for estimating overall AEE in preschool children.
• The Pfeiffer equation shows reasonable performance for classifying MVPA in this age group.
• Recommended cut-points for classifying sedentary behavior (≤6 counts·15s⁻¹), light-intensity physical activity (7–286 counts·15s⁻¹), and MVPA (≥287 counts·15s⁻¹) are proposed for preschoolers.