International Journal of Exercise Science 14(2): 1027-1035, 2021. Previous research has shown that various modes of exercise may elicit significant increases in resting metabolism for up to 24 hours post-exercise, but typically using untrained or moderately active subjects. The purpose of the present study was to compare excess post-exercise oxygen consumption (EPOC) between circuit-style resistance training (RT) and high-intensity interval training (HIIT) in young, aerobically fit women. During the follicular phase of the menstrual cycle, seven participants reported to the laboratory for evening and morning baseline resting metabolic rate (RMR) measurements via indirect calorimetry. Participants fasted and slept overnight in the laboratory between RMR measurements. Following the morning RMR measurement, participants were randomly assigned to complete either a total-body, circuit-style RT protocol (30 seconds of lifting at 80% 1RM:one minute rest) or treadmill HIIT (30-second run at 90% VO2 max:one minute stationary recovery). RMR was repeated 14 and 24 hours post-exercise. All procedures were replicated during the follicular phase of the next menstrual cycle using the remaining exercise protocol. Resting VO2 was significantly (p\u3c0.05) higher 14 hours after RT (3.8±0.3 ml/kg/min) compared to baseline (3.4±0.3 ml/kg/min), however HIIT showed no significant change (3.7±0.3 ml/kg/min). Both RT and HIIT showed significantly higher energy expenditure 14 hours post-exercise (33±5 and 33±4 kcals/30 minutes, respectively) compared to baseline (30±3 kcal). Neither protocol sustained a RMR change at 24 hours. Based on the magnitude and duration of post-exercise energy expenditure, EPOC responses may be a worthwhile consideration when prescribing exercise for weight maintenance in young, fit women
