Effect of exercise intensity, duration and mode on post-exercise oxygen consumption.

In the recovery period after exercise there is an increase in oxygen uptake termed the 'excess post-exercise oxygen consumption' (EPOC), consisting of a rapid and a prolonged component. While some studies have shown that EPOC may last for several hours after exercise, others have concluded that EPOC is transient and minimal. The conflicting results may be resolved if differences in exercise intensity and duration are considered, since this may affect the metabolic processes underlying EPOC. Accordingly, the absence of a sustained EPOC after exercise seems to be a consistent finding in studies with low exercise intensity and/or duration. The magnitude of EPOC after aerobic exercise clearly depends on both the duration and intensity of exercise. A curvilinear relationship between the magnitude of EPOC and the intensity of the exercise bout has been found, whereas the relationship between exercise duration and EPOC magnitude appears to be more linear, especially at higher intensities. Differences in exercise mode may potentially contribute to the discrepant findings of EPOC magnitude and duration. Studies with sufficient exercise challenges are needed to determine whether various aerobic exercise modes affect EPOC differently. The relationships between the intensity and duration of resistance exercise and the magnitude and duration of EPOC have not been determined, but a more prolonged and substantial EPOC has been found after hard- versus moderate-resistance exercise. Thus, the intensity of resistance exercise seems to be of importance for EPOC. Lastly, training status and sex may also potentially influence EPOC magnitude, but this may be problematic to determine. Still, it appears that trained individuals have a more rapid return of post-exercise metabolism to resting levels after exercising at either the same relative or absolute work rate; however, studies after more strenuous exercise bouts are needed. It is not determined if there is a sex effect on EPOC. Finally, while some of the mechanisms underlying the more rapid EPOC are well known (replenishment of oxygen stores, adenosine triphosphate/creatine phosphate resynthesis, lactate removal, and increased body temperature, circulation and ventilation), less is known about the mechanisms underlying the prolonged EPOC component. A sustained increased circulation, ventilation and body temperature may contribute, but the cost of this is low. An increased rate of triglyceride/fatty acid cycling and a shift from carbohydrate to fat as substrate source are of importance for the prolonged EPOC component after exhaustive aerobic exercise. Little is known about the mechanisms underlying EPOC after resistance exercise.