Brain adenosine and endurance performance

Abstract

It is now well established that the brain can limit endurance performance. However, the precise mechanisms are still unclear. From a neurochemical perspective, previous research has focused primarily on neurotransmitters like serotonin. Here focus on adenosine, a naturally occurring purine nucleoside that forms from the breakdown of adenosine triphosphate. This metabolite has effects throughout the whole body including the brain. First we present in vitro studies on how adenosine accumulates in the brain during prolonged activity, and how it affects neuron function. Then we will review animal studies on the interaction of adenosine with the dopaminergic system in regulating effort-based decision-making during physical tasks including tests of endurance performance. Finally, we will use a psychobiological approach to analyse the effects of brain adenosine in humans. The main assumption is that endurance performance is limited by an effort-based decision-making process involving the perception of effort and the maximum effort an individual is willing to exert in order to succeed in the task (potential motivation). Therefore, we will review studies using adenosine antagonists (caffeine) and conditions associated with adenosine accumulation in the brain (mental fatigue and sleep deprivation) to explore the effects of adenosine on perception of effort (and its neural correlates), potential motivation and endurance performance in humans. Finally, potential practical applications to improve the physical performance of soldiers we will discussed.