Comparisons of prediction equations for estimating energy expenditure in youth

Objectives: The purpose of this study was to compare the validity of Actigraph 2-regression models (2RM) and 1-regression models (1RM) for estimation of EE in children. Design: The study used a cross-sectional design with criterion estimates from a metabolic cart. Methods: A total of 59 children (7-13yrs) performed 12 activities (randomly selected from a set of 24 activities) for 5min each, while being concurrently measured with an Actigraph GT3X and indirect calorimetry. MET_RMR (MET considering one's resting metabolic rate) for the GT3X was estimated applying 2RM with vector magnitude (VM2RM) and vertical axis (VA2RM), and four standard 1RMs. The validity of the 2RMs and 1RMs was evaluated using 95% equivalence testing and mean absolute percent error (MAPE). Results: For the group-level comparison, equivalence testing revealed that the 90% confidence intervals for all 2RMs and 1RMs were outside of the equivalence zone (range: 3.63, 4.43) for indirect calorimetry. When comparing the individual activities, VM2RM produced smaller MAPEs (range: 14.5-45.3%) than VA2RM (range, 15.5-58.1%) and 1RMs (range, 14.5-75.1%) for most of the light and moderate activities. Conclusions: None of the 2RMs and 1RMs were equivalent to indirect calorimetry. The 2RMs showed smaller individual-level errors than the 1RMs.