PURPOSE To establish physical activity (PA) intensity cutpoints for a wrist-mounted GeneActiv accelerometer (ACC) in elementary school-aged children. A second purpose was to apply cutpoints to a free-living sample and examine duration of PA based on continuous 1s epochs. METHODS Metabolic and ACC data were collected during nine typical activities in 24 children ages 6–11. Measured VO2 values were divided by Schofield-estimated resting values to determine METs. ACC data were collected at 75 Hz, band pass filtered and averaged over each one-second interval. Receiver Operator Characteristic (ROC) curves were used to establish cutpoints at <1.5, 1.5–3, 3–6 and ≥6 METs for sedentary, light, moderate and vigorous activity, respectively. These cutpoints were applied to a free-living independent data set to quantify the amount of moderate-vigorous PA (MVPA) and to examine how bout length (1, 2, 3, 5, 10, 15 and 60 seconds) affected the accumulation of MVPA. RESULTS ROC yielded areas under the curve of 0.956, 0.946 and 0.940 for sedentary, moderate and vigorous intensities, respectively. Cutpoints for sedentary, moderate and vigorous intensities were 0.190, 0.314 and 0.998 g, respectively. Intensity classification accuracies ranged from 27.6% (light) to 88.7% (vigorous) when cutpoints were applied to the calibration data. When applied to free-living data (n=47 children ages 6–11), estimated daily MVPA was 308 minutes and decreased to 14.3 minutes when only including 1 min periods of continuous MVPA. CONCLUSION Cutpoints that quantify movements associated with moderate-vigorous intensity, when applied to a laboratory protocol, result in large amounts of accumulated MVPA using the 1s epoch compared to prior studies, highlighting the need for representative calibration activities and free-living validation of cutpoints and epoch length selection.

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The purpose of this study was to determine the ability of first-, third-, and fifth-graders to accurately self-report height and weight. Self-reported and measured values for height and weight were recorded for 487 students. The ability to self-report a reasonable value for height and weight improved with grade level, but children in all 3 grade levels significantly underreported their height and weight. Only fifth-graders accurately self-reported their weight; therefore, using self-reported height and weight to determine the prevalence of overweight and obesity for elementary school–aged children is not recommended.

Background The America on the Move (AOM) Family Intervention Program has been shown to prevent excess weight gain in overweight children. Providing intervention materials via the internet would have the potential to reach more families but may increase sedentary behavior. The purpose was to evaluate whether delivering the AOM Family Intervention via the internet versus printed workbook would have a similar impact on sedentary behaviors in children. Methods 131 children (age 8–12) were randomized to receive the AOM Family Intervention via the internet or workbook for 12 weeks. Changes in objectively measured sedentary time and moderate-to vigorous physical activity (MVPA) as well as self-reported screen time were compared between groups. Results There were no significant differences between groups in screen time, sedentary time, or MVPA at the end of the 12 week intervention. Families receiving the intervention via the internet were more likely to remain in the study (98% vs. 82%, P = .016). Conclusions Using the internet to deliver the lifestyle intervention did not increase sedentary behavior in children. Attrition rates were lower when the program was delivered by internet versus via printed materials. These results provide support for using the internet to deliver healthy lifestyle programs for children.

This study established wrist-mounted Actical cutpoints for children using 2 methods. The differences in cutpoints and their effect on estimates of MVPA in an independent sample highlight challenges associated with establishing cutpoints, suggesting that standardized calibration procedures be developed.