Excess post-exercise oxygen consumption (EPOC, informally called afterburn) is a measurably increased rate of
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
intake following strenuous
activity. In historical contexts the term "oxygen debt" was popularized to explain or perhaps attempt to quantify
anaerobic energy
Anaerobic exercise is a type of exercise that breaks down glucose in the body without using oxygen; ''anaerobic'' means "without oxygen". In practical terms, this means that anaerobic exercise is more intense, but shorter in duration than aerobi ...
expenditure, particularly as regards
lactic acid
Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as natu ...
/
lactate metabolism; in fact, the term "oxygen debt" is still widely used to this day. However, direct and indirect
calorimeter
A calorimeter is an object used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Differential scanning calorimeters, isothermal micro calorimeters, titration calorimete ...
experiments have definitively disproven any association of lactate metabolism as causal to an elevated oxygen uptake.
In recovery, oxygen (EPOC) is used in the processes that restore the body to a
resting state and adapt it to the
exercise
Exercise is a body activity that enhances or maintains physical fitness and overall health and wellness.
It is performed for various reasons, to aid growth and improve strength, develop muscles and the cardiovascular system, hone athletic ...
just performed. These include:
hormone
A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...
balancing, replenishment of fuel stores,
cell
Cell most often refers to:
* Cell (biology), the functional basic unit of life
Cell may also refer to:
Locations
* Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...
ular repair, innervation, and
anabolism. Post-exercise oxygen consumption replenishes the
phosphagen system. New ATP is synthesized and some of this ATP donates phosphate groups to
creatine
Creatine ( or ) is an organic compound with the nominal formula (H2N)(HN)CN(CH3)CH2CO2H. It exists in various modifications (tautomers) in solution. Creatine is found in vertebrates where it facilitates recycling of adenosine triphosphate ( ...
until ATP and creatine levels are back to resting state levels again. Another use of EPOC is to fuel the body’s increased metabolism from the increase in body temperature which occurs during exercise.
EPOC is accompanied by an elevated consumption of fuel. In response to exercise, fat stores are broken down and
free fatty acids
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, f ...
(FFA) are released into the blood stream. In recovery, the direct oxidation of free fatty acids as fuel and the energy consuming re-conversion of FFAs back into fat stores both take place.
Duration of the effect
The EPOC effect is greatest soon after the exercise is completed and decays to a lower level over time. One experiment, involving exertion above baseline, found EPOC increasing
metabolic
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
rate to an excess level that decays to 13% three hours after exercise, and 4% after 16 hours, for the studied exercise dose. Another study, specifically designed to test whether the effect existed for more than 16 hours, conducted tests for 48 hours after the conclusion of the exercise and found measurable effects existed up to the 38-hour post-exercise measurement, for the studied exercise dose.
Size of the EPOC effect
Studies show that the EPOC effect exists after both
aerobic exercise
Aerobic exercise (also known as endurance activities, cardio or cardio-respiratory exercise) is physical exercise of low to high intensity that depends primarily on the aerobic energy-generating process. "Aerobic" is defined as "relating to, inv ...
and
anaerobic exercise
Anaerobic exercise is a type of exercise that breaks down glucose in the body without using oxygen; ''anaerobic'' means "without oxygen". In practical terms, this means that anaerobic exercise is more intense, but shorter in duration than aerobi ...
. In a 1992 Purdue study, results showed that high intensity, anaerobic type exercise resulted in a significantly greater magnitude of EPOC than aerobic exercise of equal work output. For exercise regimens of comparable duration and intensity, aerobic exercise burns more
calorie
The calorie is a unit of energy. For historical reasons, two main definitions of "calorie" are in wide use. The large calorie, food calorie, or kilogram calorie was originally defined as the amount of heat needed to raise the temperature of on ...
s during the exercise itself, but the difference is partly offset by the higher increase in caloric expenditure that occurs during the EPOC phase after anaerobic exercise. Anaerobic exercise in the form of
high-intensity interval training
High-intensity interval training (HIIT) is a training protocol alternating short periods of intense or explosive anaerobic exercise with brief recovery periods until the point of exhaustion. HIIT involves exercises performed in repeated quick bu ...
was also found in one study to result in greater loss of
subcutaneous fat
The subcutaneous tissue (), also called the hypodermis, hypoderm (), subcutis, superficial fascia, is the lowermost layer of the integumentary system in vertebrates. The types of cells found in the layer are fibroblasts, adipose cells, and mac ...
, even though the subjects expended fewer than half as many calories during exercise. Whether this result was caused by the EPOC effect has not been established, and the caloric content of the participants' diet was not controlled during this particular study period.
Most researchers use a measure of EPOC as a natural part of the quantification or measurement of exercise and recovery energy expenditure; to others this is not deemed necessary. After a single bout or set of weight lifting, Scott et al. found considerable contributions of EPOC to total energy expenditure. In their 2004 survey of the relevant literature, Meirelles and Gomes found: "In summary, EPOC resulting from a single resistance exercise ''session'' (i.e., many lifts) does not represent a great impact on energy balance; however, its cumulative effect may be relevant". This is echoed by Reynolds and Kravitz in their survey of the literature where they remarked: "the overall weight-control benefits of EPOC, for men and women, from participation in resistance exercise occur over a significant time period, since kilocalories are expended at a low rate in the individual post-exercise sessions."
The EPOC effect clearly increases with the intensity of the exercise, and (at least in the case of aerobic exercise, perhaps also for anaerobic) the duration of the exercise.
Studies comparing intermittent and continuous exercise consistently show a greater EPOC response for higher intensity, intermittent exercise.
See also
*
High-intensity interval training
High-intensity interval training (HIIT) is a training protocol alternating short periods of intense or explosive anaerobic exercise with brief recovery periods until the point of exhaustion. HIIT involves exercises performed in repeated quick bu ...
*
Exercise physiology
Exercise physiology is the physiology of physical exercise. It is one of the allied health professions, and involves the study of the acute responses and chronic adaptations to exercise. Exercise physiologists are the highest qualified exercise ...
*
Yo-yo effect
Weight cycling, also known as yo-yo dieting, is the repeated loss and gain of weight, resembling the up-down motion of a yo-yo. Many dieters are initially successful in the pursuit of weight loss but unsuccessful in maintaining the loss long-term ...
References
Further reading
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*Hayes, Sean (2022), "Burning Fat & Calories Post-Workout via the Afterburn Effect/EPOC.
The Pliagility Blog.
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{{DEFAULTSORT:Excess Post-Exercise Oxygen Consumption
Exercise physiology
de:EPOC (Sportwissenschaft)