POSTEXERCISE ENERGY-EXPENDITURE AND SUBSTRATE OXIDATION IN YOUNG-WOMEN RESULTING FROM EXERCISE BOUTS OF DIFFERENT INTENSITY

Objective: The effects of low and high intensity exercise, of similar energy output, on exercise and post-exercise energy expenditure and su bstrate oxidation were studied in eight active, eumenorrheic females ( aged 22 to 31). Methods: Continuous indirect calorimetry was performed during cycle ergometry exercise and for 3 hours following each of the following three protocols administered in random order: 1) low intens ity exercise (LIE: 500 calories 50% VO2 max), 2) high intensity exerci se (HIE: 500 calories 75% VO2 max), and 3) control condition (C) of qu iet sitting for 1 hour, rather than exercise. Excess postexercise oxyg en consumption (EPOC), energy expenditure and total fat and carbohydra te oxidation for the entire exercise/control plus 3-hour recovery peri od were determined by indirect calorimetry. Results: Mean EPOC for the 3-hour post-exercise period for HIE (9.0+/-1.7 L, 41 kcals) was signi ficantly greater than EPOC for low intensity exercise (4.8+/-1.6 L, 22 kcals). Oxygen consumption (VO2) following HIE, but not LIE remained elevated at the end of the 3-hour post-exercise period. Total carbohyd rate oxidation (exercise plus postexercise period) was significantly h igher for HIE (116+/-8.6 g) compared to LIE (85.0+/-5.2 g). Total fat oxidation was lower for HIE (27.7+/-3.3 g) compared to LIE (36.9+/-3.0 g), but this difference did not reach statistical significance (p=0.0 7). At the end of the 3-hour recovery period, the rate of fat oxidatio n was higher following HIE compared to LIE. Conclusion: These data ind icate that the recovery period should also be considered when determin ing the impact of different exercise intensities on total energy expen diture and fat and carbohydrate utilization in women.