Moderate-to-vigorous physical activity among children: discrepancies in accelerometry-based cut-off points

Objective: To highlight the discrepancies in accelerometry cut‐off points of moderate‐to‐vigorous physical activity (MVPA) according to the definitions of Puyau et al. (MVPA^P) and Trost et al. (MVPA^T). Research Methods and Procedures: Forty‐five children from 8 to 11 years old were monitored with the ActiGraph (ActiGraph, LLC, Fort Walton Beach, FL) for 3 consecutive days. Daily time spent at MVPA obtained with MVPA^P was compared with that obtained with MVPA^T using variability, regression, and agreement statistics. Data were then discussed with regard to physical activity recommendations. Results: The mean daily time spent at MVPA^P (28 ± 18 minutes) was significantly lower (p < 10^?4) than that spent at MVPA^T (141 ± 39 minutes). The coefficient of determination between the two definitions was low (R² = 0.49 ± 0.71). There was a lack of agreement between the two definitions, with a mean error or bias of 113 min/d. Thirty‐four point eight percent and 100% of children underwent 30‐minute MVPA/d with MVPA^P and MVPA^T definitions, respectively. Discussion: Comparability between studies devoted to describing children's physical activity or to assessing interventions may lack consistency according to the definition, with a real risk of misclassification.