The Effect of Varying Intensity on Total Energy Expenditure During Circuit Weight-Training with Equal Volume

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In studies involving total energy expenditure (net exercise VO2 + net recovery VO2) during circuit weight-training, few have focused on the effect of variable training intensities, in which the training volumes (intensity X sets X repetitions) are equal. PURPOSE: This study was designed to test the potential differences in total energy expenditure (TEE) following circuit weight-training under two different intensities, in which the sets and repetitions were adjusted to keep training volumes equal. METHODS: Thirteen physically active, college-age males and females (males = 4; females = 9; mean age = 20.7 yr.) were tested using a 3-station weight-training circuit (seated chest-press, supine leg-press, and seated lat pull down), minimum 3 sets, with one minute between sets, under two intensities (70% and 85% of 1RM). Training volumes were equated for total pounds lifted by adjusting the intensity, sets, and repetitions during each trial. Trials were conducted in random order, on separate days, with a minimum of 48 hr between each. VO2 was monitored using a Cosmed™ K4b2 portable system for 15 minutes pre-exercise (resting), during exercise, and post-exercise until VO2 returned to resting values. Energy expenditure was calculated from VO2using indirect calorimetry, in which 1 liter of oxygen consumed equals 5 kcal of energy. RESULTS: TEE values were significantly higher during 85% intensity trials (60.25 ± 6.33 kcal) than 70% trials (54.23 ± 5.60 kcal) with higher repetitions in the latter equalizing training volume (P = 0.024). When breaking TEE down into net exercise and net recovery energy expenditures, recovery energy expenditure was a significantly larger contributing factor in TEE. Recovery energy expenditure was 12.28 ± 6.3 kcal at 85% intensity, and 9.77 ± 5.4 kcal at 70% intensity (P = .029) CONCLUSIONS: These results suggest that heavier resistance with fewer repetitions creates a greater recovery O2 demand and thus greater TEE, than lower resistance with more repetitions, despite equal training volumes.