Calibration of two objective measures of physical activity for children

TLDR

The study aimed to calibrate ActiGraph and Actical accelerometers to classify activity intensity in children aged 5–8. Thirty‑three children wore both accelerometers and a portable metabolic system during rest and nine activities, and ROC analysis of breath‑by‑breath oxygen consumption data was used to derive cutpoints that maximised sensitivity and specificity. The accelerometers achieved near‑perfect discrimination of sedentary behavior (AUC ≥ 0.98) and acceptable discrimination of moderate (AUC ≈ 0.85–0.86) and vigorous activity (AUC ≈ 0.83–0.86), indicating they can reliably distinguish activity intensity levels in children 5–8.

Abstract

A calibration study was conducted to determine the threshold counts for two commonly used accelerometers, the ActiGraph and the Actical, to classify activities by intensity in children 5 to 8 years of age. Thirty-three children wore both accelerometers and a COSMED portable metabolic system during 15 min of rest and then performed up to nine different activities for 7 min each, on two separate days in the laboratory. Oxygen consumption was measured on a breath-by-breath basis, and accelerometer data were collected in 15-s epochs. Using receiver operating characteristic curve (ROC) analysis, cutpoints that maximised both sensitivity and specificity were determined for sedentary, moderate and vigorous activities. For both accelerometers, discrimination of sedentary behaviour was almost perfect, with the area under the ROC curve at or exceeding 0.98. For both the ActiGraph and Actical, the discrimination of moderate (0.85 and 0.86, respectively) and vigorous activity (0.83 and 0.86, respectively) was acceptable, but not as precise as for sedentary behaviour. This calibration study, using indirect calorimetry, suggests that the two accelerometers can be used to distinguish differing levels of physical activity intensity as well as inactivity among children 5 to 8 years of age.