EPOC stands for excess post-exercise oxygen consumption. EPOC is also known as the after burn. During any form of exercise the body requires oxygen at a higher rate than it does at rest. This increased demand for oxygen creates an oxygen deficit that accrues during exercise. Like any deficit (except the ones the US Government creates) this oxygen deficit needs to be paid off. EPOC represents the payment of this oxygen debt during the recovery period.
EPOC restores the body to its resting state and fuels the processes that enable to the body to adapt to exercise. During EPOC several physiologic processes are occurring simultaneously. This recovery period can sometimes last up to 48 hours (the length depends on the intensity/duration of the exercise and one’s baseline fitness level).
During EPOC fuel is burned at a higher rate. In other words, metabolism is increased and that’s one reason why there is growing interest in EPOC. Higher metabolism means better weight control. Higher metabolism ensues because it takes energy to restore the body to its normal resting state.
Physiologic Processes Restored During EPOC
- Energy stores are replenished.
- Blood is re-oxygenated.
- Hormones levels return to normal.
- Body temperature falls to normal.
- Heart rate and ventilation (breathing) return to normal
During EPOC the creatine-phosphate energy system used during anaerobic metabolism is replenished through the regeneration of ATP. Fatty acids needed for aerobic metabolism (oxidative energy pathway) are replenished, too.
Exercise is accompanied by increases in cortisol and epinephrine in the case of aerobic and anaerobic exercise as well as increases in growth hormone and testosterone with resistance training and high intensity interval training. These hormone levels are restored to normal during EPOC.
Body temperature, heart rate, and breathing are increased during exercise and return to normal during EPOC. The more they increase the longer it takes to them to return to resting levels.
EPOC and Weight Control
As we mentioned EPOC is associated with higher metabolism. Studies have been performed to see which exercise(s) effect EPOC and metabolism the most. Comparing exercises can be difficult because of differences in intensity and duration between exercises.
As a rule of thumb high intensity interval training causes a greater EPOC and is associated with greater subcutaneous fat loss than aerobic exercises even though aerobic exercise is associated with higher calorie burning during the performance of the actual exercise. This is because high intensity interval training alters body physiology to a greater degree than do aerobics and requires greater energy to restore the physiology to normal.
One study looking at resistance training found that metabolism is 13% higher above baseline at 3 hours post exercise and 4% higher at 16 hours. This elevation in metabolism can last up to 48 hours based on another study.
It has been determined that an additional 51 to 127 calories are burned during EPOC. This may not seem like a lot, and it really isn’t. This is one reason we say that when it comes to weight loss the best bang for the buck comes from dietary changes. Having said that, though, exercise can contribute to weight loss/weight maintenance. But, the weight management benefits of exercise occur over time from regular exercise. From a weight loss only perspective high intensity interval training appears to provide greater benefit than aerobics.