Accuracy of estimated energy expenditure from caloric display of an elliptical trainer

Purpose: The purpose of this study was to examine the accuracy of the energy expenditure estimation of a commercially available elliptical trainer. Methods: Twenty-nine participants (age range: 18-28 yr; 14 males, 15 females) completed two bouts of exercise on a Precor EFX 556i elliptical trainer at 40% and 70% of their heart rate reserve (HRR). Participants exercised for 15 minutes at each intensity on two separate days and the order of the intensities were randomized. During the last 10 minutes of each bout, energy expenditure was recorded from the caloric display of the elliptical trainer and from a metabolic cart via indirect calorimetry. Additionally, heart rate and rating of perceived exertion (RPE) was recorded each minute. Energy expenditure obtained from the metabolic cart was reported as both ???gross??? expenditure, which includes resting metabolism, and ???net??? expenditure, which does not include resting\ud metabolism. A 2 (Sex) X 2 (Modality) X 2 (Intensity) analyses of variance was used to examine differences in caloric expenditure. Results: When examining gross energy expenditure, there were main effects of sex, modality and intensity, such that energy expenditure was greater when measured on the elliptical trainer and also at 70% HRR. There was further a modality X sex interaction such that the difference in energy expenditure between the two modalities was greater in females at 70% HRR. When examining net energy expenditure, there were main effects of sex, modality and intensity as previously described, but no interactions were present. Conclusion: The data from this study suggests that the Precor EFX 556i elliptical trainer overestimates energy expenditure for both males and females. Furthermore, the elliptical trainer appears to overestimate energy expenditure even more so in females at higher intensities