Agreement Between Different Days of activPAL and Actigraph GT3X Measurement of Sedentary Behavior and Physical Activity During the School Hours in Elementary Children

Introduction: The authors’ objective was to identify the minimum number of days required to measure sedentary behavior and physical activity in children during school hours. Methods: Fifty-three children from four classes of the second year of elementary school in a public school in Brazil were selected. Sedentary behavior and physical activity were evaluated using activPAL in the thigh and ActiGraph GT3X on the hip. The devices were used for 4 days during the 4 hr of school. Intraclass correlation coefficient (ICC) and Bland–Altman plots were used for statistical analysis (p <.05). Results: For sedentary/ stationary behavior indicators, 1 day showed good agreement with 4 days (sitting time, ICC =.89; bias [limits of agreement 95%, LA95%] = 1.6 [45.1 to −41.9], standing time, ICC =.93; bias [LA95%] 1.1 [30.2 to −28.0], and stationary behavior, ICC =.56; bias [LA95%] = 0.2 [37.2 to −36.7]). However, 2 days were necessary for good agreement, with 4 days for physical activity indicators (walking time, ICC =.91; bias [LA95%] = 1.1 [12.0 to −9.7], light physical activity, ICC =.97; bias [LA95%] = 0.3 [7.6 to −7.0], moderate physical activity, ICC =.93; bias [LA95%] = 0.3 [2.3 to −1.6], and vigorous physical activity, ICC =.93; bias [LA95%] = 0.3 [3.1 to −2.5]). Conclusion: Therefore, 1 evaluation day seems enough to obtain representative data of school sedentary/stationary behavior, while 2 days are necessary for the evaluation of physical activity indicators during school hours.