What Is EPOC or Excess Post-Exercise Oxygen Consumption?
Definition of EPOC
EPOC, or Excess Post-Exercise Oxygen Consumption is a measure of increased oxygen consumption after exercise or strenuous activity. EPOC is also accompanied by a post-exercise increase in energy or fuel consumption (also characterized as an increase in metabolism.) EPOC is also known as “oxygen debt” or “oxygen deficit.” In bodybuilding and fitness training circles it may also be called “exercise afterburn.”
EPOC occurs after both aerobic (cardiovascular) exercise and anaerobic exercise like weight training.
Following cardiovascular exercise or weight training, the body continues to require oxygen at a level that exceeds oxygen requirements when the exercise began.
There are a number of explanations for why oxygen consumption after exercise is higher than before exercise. Most of these revolve around the body restoring itself to a state of homeostasis. After exercise the body has to:
Replenish energy stores (such as ATP and muscle glycogen)
Re-oxygenate the blood
Restore body temperature levels to a pre-exercise state
Restore pre-exercise breathing and heart-rate levels
All of these processes require the consumption of additional oxygen, as well as energy, after exercise.
In other words, restoring the body to its pre-exercise state is work. And work means additional expenditure of energy beyond the energy consumed to perform that work.
EPOC and HIIT
Clinical research suggests that EPOC is greatest after high intensity cardio training, specifically HIIT.
However, this remains controversial, with some research indicating that the EPOC HIIT connection is nothing more than a myth.
However, the actual amount of EPOC and the duration is widely disputed.
Some studies show EPOC persisting for up to 24 hours following completion of high intensity cardio, while others challenge this, showing EPOC levels returning to normal in less than 90 minutes.
Even the studies that do show prolonged increases in EPOC lasting up to 24 hours have to be taken in context.
A study by Maehlum et al. and published in the journal Metabolism, found that increases in VO2 of 5% on average persisted in trainees for up to 24 hours who had performed high intensity cardio training for 90 minutes at 70% VO2Max.
However, for a person on a 2000 calorie diet, a 5 percent increase in VO2 over 24 hours would result in an extra 25 calories being burned as a result of the EPOC effect. While that’s better than zero extra calories, it’s not particularly significant.