Question

Describe two causes of BOTH the fast and the slow phase of EPOC (excess post-exercise oxygen consumption).

Answer 1

Answer:-

Excess post-exercise oxygen consumption (EPOC) :-

Hill formulated a hypothesis in 1920s that the classical oxygen debt was an attempt to link the metabolism of lactic acid with the O₂ consumption in excess of resting that occurs after exercise. The oxygen debt was hypothesized to represent the oxidation of a minor fraction of the lactate formed during exercise, to provide the energy to reconvert the remainder of the lactate to glycogen during recovery. Margaria et al. in 1933 modified this hypothesis by distinguishing between initial, fast (alactacid), and second, slow (lactacid), O₂ debt curve components. They hypothesized that due to the restoration of phosphagen (ATP+CP), the fast phase of the post exercise O₂ consumption curve is obtained. Likely it is now that the original lactic acid explanation of the oxygen debt was more simplistic. Numerous studies on several species have provided evidence demonstrating a dissociation between the kinetics of lactate removal and the slow components of the post exercise VO_2. The metabolism of lactate, a readily oxidisable substrate, following exercise appears to be directed primarily towards energy production in mitochondria. At the end of exercise the overhead concentration of lactate present may be viewed as a source of carbon, which may serve as a reservoir of oxidative ATP production or as a source of skeletons of carbon for the synthesis of glycogen, amino acids, glucose and intermediates of TCA cycle. The metabolic basis of the elevated post exercise VO₂ may be understood in terms of those factors which directly or indirectly influence mitochondrial O₂ consumption. Catecholamines, thyroxine, glucocorticoids, fatty acids, calcium ions and temperature are the factors which included among these. Of these, elevated temperature is perhaps most important. The term oxygen debt be used to describe a set of phenomena during recovery from exercise as it is not a complete explanation of the post exercise metabolism. The term alactacid debt and lactacid debt, which suggest a mechanism, are inappropriate. Use of alternative terms, e.g., '' Excess Post-exercise Consumption '' (EPOC) and recovery O₂, will avoid implication of causality in describing the elevation in metabolic rate above resting levels after exercise.