Excess post-exercise oxygen consumption

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Excess post-exercise oxygen consumption (EPOC, informally called afterburn) is a measurably increased rate of oxygen intake following strenuous activity. In historical contexts the term "oxygen debt" was popularized to explain or perhaps attempt to quantify anaerobic energy expenditure, particularly as regards lactic acid/lactate metabolism; in fact, the term "oxygen debt" is still widely used to this day. However, direct and indirect calorimeter 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 just performed. These include: hormone balancing, replenishment of fuel stores, cellular 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 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 (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.

Video Excess post-exercise oxygen consumption

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 found EPOC increasing metabolic rate to an excess level that decays to 13% three hours after exercise, and 4% after 16 hours. 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.

Maps Excess post-exercise oxygen consumption

Size of the EPOC effect

Studies show that the EPOC effect exists after both anaerobic exercise and aerobic exercise. Such comparisons are problematic, however, in that it is difficult to equalize and subsequently compare workloads between the two types of exercise. For exercise regimens of comparable duration and intensity, aerobic exercise burns more calories 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 was also found in one study to result in greater loss of subcutaneous fat, 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.

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.

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.

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See also

• High-intensity interval training
• Yo-yo effect

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References

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Further reading

• Hill, A. V.; Long, C. N. H.; Lupton, H. (1924). "Muscular Exercise, Lactic Acid, and the Supply and Utilisation of Oxygen". Proceedings of the Royal Society B: Biological Sciences. 96 (679): 438-75. doi:10.1098/rspb.1924.0037. JSTOR 81203. 
• Laforgia, J.; Withers, R. T.; Gore, C. J. (2006). "Effects of exercise intensity and duration on the excess post-exercise oxygen consumption". Journal of Sports Sciences. 24 (12): 1247-64. doi:10.1080/02640410600552064. PMID 17101527. 
• Lee, C. G. (2003). "Excess post-exercise oxygen consumption in adult sockeye (Oncorhynchus nerka) and coho (O. Kisutch) salmon following critical speed swimming". Journal of Experimental Biology. 206 (18): 3253-60. doi:10.1242/jeb.00548. PMID 12909706. 
• Thornton, M. K.; Potteiger, J. A. (2002). "Effects of resistance exercise bouts of different intensities but equal work on EPOC". Medicine and science in sports and exercise. 34 (4): 715-22. doi:10.1249/00005768-200204000-00024. PMID 11932584. 
• Gore, C. J.; Withers, R. T. (1990). "The effect of exercise intensity and duration on the oxygen deficit and excess post-exercise oxygen consumption". European Journal of Applied Physiology and Occupational Physiology. 60 (3): 169-74. doi:10.1007/BF00839153. PMID 2347316. 
• Lee, C. G.; Devlin, R. H.; Farrell, A. P. (2003). "Swimming performance, oxygen consumption and excess post-exercise oxygen consumption in adult transgenic and ocean-ranched coho salmon". Journal of Fish Biology. 62 (4): 753-66. doi:10.1046/j.1095-8649.2003.00057.x. 
• Lecheminant, J.; Jacobsen, D.; Bailey, B.; Mayo, M.; Hill, J.; Smith, B.; Donnelly, J. (2008). "Effects of Long-Term Aerobic Exercise on EPOC". International Journal of Sports Medicine. 29 (1): 53-8. doi:10.1055/s-2007-965111. PMID 17879880. 
• Matsuo, Tomoaki; Ohkawara, Kazunori; Seino, Satoshi; Shimojo, Nobutake; Yamada, Shin; Ohshima, Hiroshi; Tanaka, Kiyoji; Mukai, Chiaki (2012). "Cardiorespiratory fitness level correlates inversely with excess post-exercise oxygen consumption after aerobic-type interval training". BMC Research Notes. 5: 646. doi:10.1186/1756-0500-5-646. PMC 3527216 . PMID 23171610. 
• Zeng, Ling-Qing; Zhang, Yao-Guang; Cao, Zhen-Dong; Fu, Shi-Jian (2010). "Effect of temperature on excess post-exercise oxygen consumption in juvenile southern catfish (Silurus meridionalis Chen) following exhaustive exercise". Fish Physiology and Biochemistry. 36 (4): 1243-52. doi:10.1007/s10695-010-9404-9. PMID 20499273. 
• Scott, Christopherb; Littlefield, Nathanaeld; Chason, Jeffreyd; Bunker, Michaelp; Asselin, Elizabethm (2006). "Differences in oxygen uptake but equivalent energy expenditure between a brief bout of cycling and running". Nutrition & Metabolism. 3: 1. doi:10.1186/1743-7075-3-1. PMC 1334197 . PMID 16390548. 
• Scott, Christopher (2005). "Misconceptions about Aerobic and Anaerobic Energy Expenditure". Journal of the International Society of Sports Nutrition. 2 (2): 32-7. doi:10.1186/1550-2783-2-2-32. PMC 2129144 . PMID 18500953. 
• Gaesser, Glenn A; Brooks, George A (1984). "Metabolic bases of excess post-exercise oxygen consumption: a review". Medicine and Science in Sports and Exercise. 16 (1): 29-43. doi:10.1249/00005768-198401000-00008. PMID 6369064. 

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