Calibration of ActiGraph GT3X, Actical and RT3 accelerometers in adolescents

Abstract The objective of this study was to develop count cut-points for three different accelerometer models: ActiGraph GT3X, RT3 and Actical to accurately classify physical activity intensity levels in adolescents. Seventy-nine adolescents (10–15 years) participated in this study. Accelerometers and oxygen consumption () data were collected at rest and during 11 physical activities of different intensities. Accelerometers were worn on the waist and was measured by a portable metabolic system: Cosmed K4b2. Receiver operating characteristic (ROC) curves were used to determine cut-points. Cut-points for sedentary (SED), moderate-to-vigorous (MVPA) and vigorous-intensity physical activity (VPA) were 46, 607 and 818 counts·15s−1 to the vertical axis of ActiGraph; 180, 757 and 1112 counts·15s−1 to the vector magnitude of ActiGraph; 17, 441 and 873 counts·15s−1 for Actical; and 5.6, 20.4 and 32.2 counts·s−1 for RT3, respectively. For all three accelerometer models, there was an almost perfect discrimination of SED and MVPA (ROC >0.97) and an excellent discrimination of VPA (ROC>0.90) observed. Areas under the ROC curves indicated better discrimination of MVPA by ActiGraph (AUC=0.994) and Actical (AUC=0.993) when compared to RT3 (AUC=0.983). The cut-points developed in this study for the ActiGraph (vector magnitude), RT3 and Actical accelerometer models can be used to monitor physical activity level of adolescents.