Calibration and validation of the ActiGraph GT3X+ in 2-3 year olds

J Sci Med Sport. 2014 Nov;17(6):617-22. doi: 10.1016/j.jsams.2013.11.005. Epub 2013 Nov 28.


Objectives: To calibrate and validate the ActiGraph GT3X+ to measure sedentary behaviour and physical activity in 2-3 year olds, using 5-s epochs; and to compare the predictive validity of the resulting cut-points with that of NHANES', Trost's, and Pate's 15-s cut-points.

Design: Cross-sectional study.

Methods: Eighteen children (2.86 ± 0.60 years) wore an ActiGraph GT3X+ during video-recorded semi-structured calibration activity sessions. Activity was coded following Children's Activity Rating Scale. Receiver Operating Characteristic analysis was used to derive Axis1 and vector magnitude cut-points for sedentary behaviour and moderate-to-vigorous physical activity at 5-s epochs. Agreement with Children's Activity Rating Scale was assessed with Cohen's kappa, Lin's concordance, and Bland-Altman plots. Predictive validity of all cut-points was assessed in an independent sample of 20 children (2.99 ± 0.48 years) video-recorded during free-play, using the same procedures as the calibration phase.

Results: During calibration, vector magnitude cut-points (sedentary behaviour ≤ 96.12 counts; moderate-to-vigorous physical activity ≥ 361.94 counts) showed slightly better classification agreement with Children's Activity Rating Scale than Axis1 cut-points (sedentary behaviour ≤ 5 counts; moderate-to-vigorous physical activity ≥ 165 counts), but the latter showed the lowest bias in estimated sedentary behaviour and moderate-to-vigorous physical activity time. In the validation sample, 5-s Axis1 cut-points showed the best predictive validity and lowest mean differences of all cut-points between predicted and observed sedentary behaviour (-2.31%), light physical activity (-24.40%), and total physical activity time (-0.95%). Moderate-to-vigorous physical activity time was significantly overestimated by all cut-points (128.33-184.17%).

Conclusions: Because moderate-to-vigorous physical activity was highly overestimated, using only the 5-s Axis1 sedentary behaviour cut-point to distinguish sedentary behaviour from total physical activity is advised. The high accuracy indicates that these cut-points are useful for epidemiological studies involving the sedentary behaviour and physical activity of 2-3 year olds.

Keywords: Accelerometer; Children; Cut-points; Physical activity; Sedentary behaviour; Triaxial.

Publication types

  • Clinical Trial
  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actigraphy / instrumentation*
  • Calibration
  • Child, Preschool
  • Cross-Sectional Studies
  • Exercise*
  • Female
  • Humans
  • Male
  • Nutrition Surveys
  • Sedentary Behavior*