Lack of sustained increase in VO2 following exercise in fit and unfit subjects

Thermogenesis after exercise was studied by measuring oxygen consumption in 23 subjects who were classified into three groups according to their routine level of physical activity. VO2 was first measured after a 30-minute rest period 4-hours after breakfast. Then each subject either exercised for 20 minutes at approximately the anaerobic threshold or on a separate non-exercise day remained recumbent. The subject then returned to, or remained, at rest. There was no significant difference in VO2 from the resting level from 40 minutes to 3 hours after exercise, between exercise and non-exercise days in any fitness group. Seven subjects also exercised for a longer period or at a higher intensity. Again, there was no significant difference in the time course of VO2 from 40 minutes to 220 minutes after exercise, between exercise and non-exercise days. Because no sustained effect of moderate or intense exercise on VO2 was demonstrated, we conclude that no appreciable caloric loss beyond that generated by the exercise period itself and the early recovery phase is found in either fit or unfit subjects. These data do not support claims for sustained increases in metabolic rate after exercise in weight-control programs.