Re-interpreting anaerobic metabolism: an argument for the application of both anaerobic glycolysis and excess post-exercise oxygen consumption (EPOC) as independent sources of energy expenditure

Abstract

Due to current technical difficulties and changing cellular conditions, the measurement of anaerobic and recovery energy expenditure remains elusive. During rest and low-intensity steady-state exercise, indirect calorimetric measurements successfully represent energy expenditure. The same steady-state O₂ uptake methods are often used to describe the O₂ deficit and excess post-oxygen consumption (EPOC): 1 l O₂ = 5 kcal = 20.9 kJ. However, an O₂ deficit plus exercise O₂ uptake measurement ignores energy expenditure during recovery, and an exercise O₂ uptake plus EPOC measurement misrepresents anaerobic energy expenditure. An alternative solution has not yet been proposed. Anaerobic glycolysis and mitochondrial respiration are construed here as a symbiotic union of metabolic pathways, each contributing independently to energy expenditure and heat production. Care must be taken when using O₂ uptake alone to quantify energy expenditure because various high-intensity exercise models reveal that O₂ uptake can lag behind estimated energy demands or exceed them. The independent bioenergetics behind anaerobic glycolysis and mitochondrial respiration can acknowledge these discrepancies. Anaerobic glycolysis is an additive component to an exercise O₂ uptake measurement. Moreover, it is the assumptions behind steady-state O₂ uptake that do not permit proper interpretation of energy expenditure during EPOC; 1 l O₂≠ 20.9 kJ. Using both the O₂ deficit and a modified EPOC for interpretation, rather than one or the other, leads to a better method of quantifying energy expenditure for higher intensity exercise and recovery.