Accurately assessing the energy expenditure (EE) of different types of physical activity is important for exercise prescription in obese individuals. The aim of this study was to examine the accuracy of the Polar S810i Heart Rate Monitor and SenseWear Pro Armband (SWA) for estimating energy expenditure (EE) during indoor rowing versus indirect calorimetry (IC). 43 overweight and obese adults (16 men, 27 women, BMI = 31.2 ± 3.7) participated in the study. Within a week after a maximal incremental test on a rowing ergometer, EE was assessed with Polar S810i, SWA and IC during two different intensities of rowing exercises (at 50% VO₂max and 70% VO₂max) on a Concept II ergometer. Data were analyzed with Pearson’s product moment correlations and repeated measures ANOVA. Post hoc multiple comparisons were performed using the Bonferroni test. Bland-Altman plots were created to assess the agreement between the EE estimates and IC measurements. At 50% VO₂max, Polar S810i and SWA significantly overestimated EE by 0.5 ± 0.50 kcal·min^-1 (p < 0.001) and by 0.9 ± 0.92 kcal·min^-1 (p < 0.001), respectively. At 70% VO₂max, no significant differences were found between the SWA and IC, and between Polar S810i and IC measurements. Bland-Altman plots showed good agreements between the measured EE and estimates by Polar S810i and SWA at 70% VO₂max. At 50% VO₂max, there was a poor agreement between SWA and IC measurements. There were high correlations among three methods at both intensities (r = 0.82 to r = 0.95). In conclusion, Polar S810i and SWA showed reasonable concordance with IC for measuring EE of the moderate intensity exercise but not the lower intensity exercise on indoor rowing in the participants of this study. Polar S810i and SWA might be useful to assess EE during indoor rowing for overweight and obese individuals who try to manage their body weight, but it is necessary to develop exercise and population specific algorithms to enhance the accuracy of SWA to estimate energy expenditure during various intensities of physical exercises.

• Polar S810i and SWA when compared to the indirect calorimetry, provide reasonable estimates of energy expenditure on rowing ergometer at the moderate exercise intensity, but not at the low exercise intensity.

• The monitor of the Concept II Model D rowing ergometer significantly overestimated the energy expenditure during low and moderate intensity exercises. However there was a moderate correlation between EE estimates of this device and indirect calorimetry measurements.