Validity of ActiGraph Child-Specific Equations during Various Physical Activities

Purpose The purpose of this study was to examine the validity of seven child-specific ActiGraph prediction equations/cut-points (Crouter vector magnitude 2-regression model (Cvm2RM), Crouter vertical axis 2RM (Cva2RM), Freedson, Treuth, Trost, Puyau and Evenson) for estimating energy expenditure (EE) and time spent in sedentary behaviors, light physical activity (LPA), moderate PA (MPA), and vigorous PA (VPA).

Methods Forty boys and 32 girls (mean+/-SD; age, 12+/-0.8 yrs) participated in the study. Participants performed eight structured activities and approximately 2-hrs of free-living activity. Activity data was collected using an ActiGraph GT3X+, positioned on the right hip, and EE (METRMR; activity VO2 divided by resting VO2) was measured using a Cosmed K4b2. ActiGraph prediction equations were compared against the Cosmed for METRMR and time spent in sedentary behaviors, LPA, MPA, VPA, and MVPA.

Results For the structured activities, all prediction methods were significantly different from measured METRMR for >= 3 activities (P<0.05), however all provided close estimates of METRMR during walking. On average, participants were monitored for 95.0+/-36.5 minutes during the free-living measurement. The Cvm2RM and Puyau methods were within 0.9 METRMR of measured free-living METRMR (P>0.05); all other methods significantly underestimated measured METRMR (P<0.05). The Cva2RM was within 9.7 minutes of measured time spent in sedentary behaviors, LPA, MPA, and MVPA, which was the best of the methods examined. All prediction equations underestimated VPA by 6.0-13.6 minutes.

Conclusion Compared to the Cosmed, the Cvm2RM and Puyau methods provided the best estimate of METRMR and the Cva2RM provided the closest estimate of time spent in each intensity category during the free-living measurement. Lastly, all prediction methods had large individual prediction errors.