Caffeine and Exercise Performance: Possible Directions for Definitive Findings

Abstract

Caffeine is one of the most studied supplements in the world. Studies correlate its use to increased exercise performance in endurance activities, as well as its possible ergogenic effects for both intermittent and strength activities. Recent findings show that caffeine may increase or decrease exercise performance. These antagonist responses may occur even when using the same dosage and for individuals with the same characteristics, making it challenging to explain caffeine's impact and applicability. This review article provides an analytic look at studies involving the use of caffeine for human physical performance, and addresses factors that could influence the ergogenic effects of caffeine on different proposed activities. These factors subdivide into caffeine effects, daily habits, physiological factors, and genetic factors. Each variable has been focused on by discussions to research related to caffeine. A better understanding and control of these variables should be considered in future research into personalized nutritional strategies.

Keywords: ADORA2A; CYP1A2; caffeine; ergogenic substances; exercise performance; genetic polymorphisms; sports nutrition.

Figure 1

Main mechanisms of action of caffeine-related to increases in training capacities. (A) Antagonistic action of caffeine and its secondary metabolites to adenosine at its receptors in the Central Nervous System (CNS), increasing alertness and decreasing perceived exertion in exercise. (B) Effect of preserving muscle glycogen from a greater distribution of fatty acids in the bloodstream and energy use under some conditions. (C) Increased release of calcium ions by a neuromuscular stimulus, enhancing contraction power in muscle fibers.

Figure 2

Main factors that could be involved in the ergogenic or ergolitic effects of caffeine supplementation applied to physical exercises. The image represents the variables related to the use of caffeine, such as the applied dosage, ingestion time, and caffeine withdrawal effects. Daily habits such as habitual consumption of food and beverage sources of caffeine and time of training should also be considered. Physiological Factors (gender and degree of training) and genetic factors related to the structures of adenosine receptors in the CNS (ADORA2A) and hepatic enzymes related to caffeine degradation (CYP1A2) are new findings that should be of relevant consideration for the elucidation of inter-individual responses to caffeine on exercise performance.