Metabolic ceiling as indicative of endurance capacity: importance of reserve oxidative capacity

Abstract

Compared with other animal species, the endurance capacity of humans is remarkable. The thesis of limiting and determining factors of endurance consider variables such as maximum oxygen (O2) consumption (VO2max), metabolic thresholds and movement economy the most importants. As the O2 and metabolic products of substrates (glucose and fatty acids) are used in muscle´s mitochondria to obtain energy by oxidative processes during long duration exercise, this is another important variable to be considered. The aim of this assay is to show that the incidence of fatigue in this kind of exercise might be related to negative changes in mitochondrial oxidative potential. Mitochondrial oxidative potential is situated between the extreme limits of its functionality, which correspond to the states 4 (rest) and 3 (VO2max). The thesis put forward here is that when this variable is close to the state 3 during prolonged intense exercise, the body depletes their possibilities to produce energy through oxidative phosphorilation, with consequent changes in metabolic thresholds and increase in the percent of VO2max used in this condition. Therefore, mitochondria function as a cellular bioenergetic thermostat during situations such as those involving prolonged strenuous exercise.