Comparing ActiGraph equations for estimating energy expenditure in older adults

Abstract

Accurate estimation of energy expenditure (EE) from accelerometer outputs remains a challenge in older adults. The aim of this study was to validate different ActiGraph (AG) equations for predicting EE in older adults. Forty older adults (age = 77.4 ± 8.1 yrs) completed a set of household/gardening activities in their residence, while wearing an AG at the hip (GT3X+) and a portable calorimeter (MetaMax 3B - criterion). Predicted EEs from AG were calculated using five equations (Freedson, refined Crouter, Sasaki and Santos-Lozano (vertical-axis, vectormagnitude)). Accuracy of equations was assessed using root-mean-square error (RMSE) and mean bias. The Sasaki equation showed the lowest RMSE for all activities (0.47 METs) and across physical activity intensities (PAIs) (range 0.18-0.48 METs). The Freedson and Santos-Lozano equations tended to overestimate EE for sedentary activities (range: 0.48 to 0.97 METs), while EEs for moderate-to-vigorous activities (MVPA) were underestimated (range: -1.02 to -0.64 METs). The refined Crouter and Sasaki equations showed no systematic bias, but they respectively overestimated and underestimated EE across PAIs. In conclusion, none of the equations was completely accurate for predicting EE across the range of PAIs. However, the refined Crouter and Sasaki equations showed better overall accuracy and precision when compared with the other methods.

Keywords: Accelerometry; aging; measurement; motion sensors; physical activity.

Conflict of interest statement

Disclosure statement

No potential conflict of interest was reported by the authors.

Figures

Figure 1.

Plots representing the difference between measured (MetaMax 3B) and predicted (ActiGraph equations using the vertical axis) energy expenditure (METs) for all activities combined The black solid line represents the trend, grey solid line represents mean bias and the dashed lines represent the 95% limits of agreement. Open circles represent women and filled circles represent men. EE: Energy expenditure; MET: Metabolic equivalent; VT: vertical axis.

Figure 2.

Plots representing the difference between measured (MetaMax 3B) and predicted (ActiGraph equations using the vector magnitude) energy expenditure (METs) for all activities combined. The black solid line represents the trend, grey solid line represents mean bias and the dashed lines represent the 95% limits of agreement. Open circles represent women and filled circles represent men. EE: Energy expenditure; MET: Metabolic equivalent; VM: vector magnitude.

Figure 3.

Mean bias and 95% limits of agreement for steady-state energy expenditure (METs) estimated from different predictive equations and indirect calorimetry (MetaMax 3B) for 16 different activities in older adults. *Significantly different from measured energy expenditure (p