Vol 6, Issue 3

Measuring Activity Energy Expenditure: Accuracy of the GT3X+ and Actiheart Monitors

April 1, 2013 - By 

Authors

David McMinn, University of Aberdeen
Rijan Acharya, University of Aberdeen
David A. Rowe, University of Strathclyde
Stuart R. Gray, University of Aberdeen
Julia L. Allan, University of Aberdeen
International Journal of Exercise Science 6(3) : 217-229, 2013. 
DOI: 10.70252/QEBT3375

Abstract

The purpose was to determine the accuracy of the GT3X+ and Actiheart monitors for estimating energy expenditure (EE) and steps. Additionally, to investigate agreement between waist- and wrist-mounted GT3X+ EE outputs. Nineteen participants (mean age=30) completed three treadmill walking trials at self-selected slow, medium, and fast speeds while wearing two GT3X+ (waist and wrist) and an Actiheart. Activity monitor EE was compared to indirect calorimetry criterion EE using Pearson correlations and ANOVAs. A Bland-Altman plot was used to investigate agreement between GT3X+ waist- and wrist-determined EE. GT3X+ determined steps were compared to researcher-counted steps using ANOVAs. EE estimates from all monitors correlated highly with the criterion (r ranged from .72 to .82). However, the GT3X+ (waist and wrist) underestimated EE during slow walking and overestimated EE during fast walking. There were no differences among GT3X+ (waist and wrist) estimates of EE and the criterion during the medium trial. Actiheart estimated EE was not significantly different from measured EE during all trials. The Bland-Altman plot indicated that at EE rates above 4 kcal·min-1, the GT3X+ worn on the wrist underestimated EE compared to when it was worn on the waist. There were no differences between GT3X+ waist-determined steps and researcher-counted steps for all trials. GT3X+ EE correlates highly with measured EE, but has poor absolute agreement during slow and fast walking. GT3X+ step estimates are accurate across the continuum of walking speeds when waist (but not wrist) mounted. Wrist-mounted device outputs are not comparable to waist-mounted outputs. The Actiheart accurately estimates EE.

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