Comparison of Acute Energy Expenditure and Rating of Perceived Exertion in Equivalent Bouts of Circuit Training and Treadmill Running.

Brewer, CB, Booher, BM, and Lawton, N. Comparison of acute energy expenditure and rating of perceived exertion in equivalent bouts of circuit training and treadmill running. J Strength Cond Res 35(3): 680-687, 2021-Circuit weight training (CT) maximizes exercise density, which may lead to an inaccurate perception of energy expenditure (EE). The purpose of this study was to compare acute EE indices and rating of perceived exertion (RPE) between CT and an equivalent bout of treadmill running (TR). College-aged men (n = 9) who regularly engaged in running and resistance training performed CT first. Circuit weight training that consisted of 10 resistance stations (40% of 1 repetition maximum, 15 repetitions, 60 b·min-1) was performed for 20 minutes. Heart rate (HR) and EE (Cosmed K4b2) were monitored continuously, and RPE was assessed consistently. A 20-min TR session was performed at the average HR maintained during CT. Dependent t-tests were used to assess differences in RPE, total EE (TEE, kcal), rate of EE (REE, kcal·min-1), and relative REE (RREE, kcal·kg-1·min-1) between CT and TR. Pearson's correlation was used to examine relationships between RPE and EE indices. Total EE was lower during CT (168.19 ± 16.42) than TR (244.20 ± 44.80); REE was lower during CT (8.49 ± 0.90) than TR (12.21 ± 2.24); and RREE was lower during CT (0.10 ± 0.02) than TR (0.15 ± 0.02) (all p < 0.001). Circuit weight training RPE (6.0 ± 1.1) was greater than TR (4.1 ± 0.6) (p < 0.001). There was no association between RPE and EE indices (p > 0.05). The average HR elicited by CT was 61% HR reserve. At equivalent HRs and duration, CT resulted in a significantly higher RPE but lower EE. It is imperative for subjects engaged in CT to understand that although CT results in HR values within an aerobic training zone and feels more strenuous, it is not associated with greater acute EE.