Oxygen consumption during recovery from prolonged submaximal cycling below the anaerobic threshold

The purpose of this study was to compare the magnitude and duration of excess post-exercise O2 consumption (EPOC) measured after submaximal cycling at three different intensities of equivalent energy cost but all performed below the anaerobic threshold (AT). Eight healthy young women performed the three cycling sessions after an initial determination of VO2max (M +/- SD) (41.8 +/- 7.0 ml.kg-1.min-1) and AT (73 +/- 5% VO2max). The high intensity (HI) exercise was performed at 65% VO2max (90% of AT workload) for 30 minutes, while the moderate (MI) and low intensity (LI) exercise sessions were performed at approximately 55% VO2max (75% AT) and -45% VO2max (60% AT) respectively, until the energy cost matched that expended in the HI condition. Prior to each exercise session baseline resting VO2 and respiratory exchange ratio (RER) were measured by open circuit spirometry at the end of a 35 min period of supine rest. These measures were also made during the exercise and recovery periods. Post-exercise VO2 was measured continuously until baseline VO2 (within 1 SD of resting value for 2 consecutive min) was reached. The duration of EPOC (13-14 min) was similar following all three exercise sessions. The gross EPOC energy expenditure and VO2 were both significantly greater (p < 0.01) following the HI (137.0 +/- 6.3 kJ and 6.63 +/- 0.30 1) condition than the MI condition (116.6 +/- 8.7 kJ and 5.69 +/- 0.42 1) but no significant differences existed between the MI and LI (107.4 +/- 5.8 kJ and 5.24 +/- 0.29 1) conditions for either of these variables. It was concluded that the magnitude of EPOC following submaximal exercise of equivalent energy cost but below the AT, is determined more by the intensity of exercise rather that the exercise energy cost.