Effect of Acclimation on Resting Energy Expenditure Measurements

Abstract

Background: Development of an acclimation protocol for use when measuring resting energy expenditure (REE) would simplify and standardize data collection. The purpose of this study was to determine if our 2 metabolic carts could be used interchangeably and to determine if excluding the first 3 or 5 minutes of data collected as an acclimation period would significantly improve the coefficients of variation (CVs) for oxygen consumed (VO₂) and carbon dioxide produced (VCO₂) when performing REE assessments with our metabolic cart systems. Methods: Thirteen healthy, nonsmoking adults ranging in age from 32 to 45 years, with activity levels ranging from sedentary to highly active, participated. Indirect calorimetry was performed twice in the morning after 30 minutes of supine resting. Subjects had fasted for 12 hours, and did not exercise within the last 24 hours. The system order for testing was randomized for the first measurement. When the first measurement was completed, subjects were crossed over for measurement using a second metabolic cart. Results: The CVs for VO₂ and VCO₂ were significantly lower when excluding the first 3 (VO₂, p = .0005), (VCO₂, p = .0024) or 5 minutes (VO₂, p = .0001, VCO₂, p = .0021) of data compared with no exclusions. No significant differences in CVs between the 3- and 5-minute exclusions were found for VO₂ (p = .3224) or VCO₂ (p = .2255). Conclusions: Clearly, our machines cannot be used interchangeably within a study. An acclimation period improves CVs of VO₂ and VCO_2. The similarities in CVs led us to adopt a 3-minute acclimation period for measuring REE.