Postexercise oxygen consumption was investigated in eight healthy subjects. The subjects exercised for about 80 minutes at 70% of their maximum VO2. Following the exercise the subjects rested in bed for 24 hours. Oxygen uptake was measured continuously during the first hour after exercise, then hourly for the next 11 hours, and finally at 24 hours after exercise. Heart rate and rectal temperature were recorded continuously during the first 12 hours and then at 24 hours after exercise. Blood was sampled hourly after exercise. The results were compared with those of an identical control experiment in which the subjects rested instead of exercising. Oxygen uptake of each time point in each subject was greater after exercise compared with the control experiment. Mean total oxygen consumption after exercise was 211 +/- 16 L/12 h as compared to 185 +/- 13 L/12 h in the control experiment (P less than 0.001). Also, the heart rate was higher during the first 12 hours following exercise than in the control study. No significant differences were observed in rectal temperature in the two experiments after the initial 30 minutes following exercise. The first meal taken after the cessation of exercise increased markedly the rate of oxygen consumption in comparison to the increase observed following the same meal in the control experiment. The respiratory exchange ratios were lower following exercise than in the control study. In conclusion, we have demonstrated that the excess postexercise oxygen consumption (EPOC), may persist for at least 12 hours, and possibly for 24 hours. Also, exercise caused enhancement of the stimulation in oxygen uptake seen after a meal.(ABSTRACT TRUNCATED AT 250 WORDS)