Caffeine is a popular supplement among athletes and is commonly consumed in energy drinks, “preworkout” products, chewing gum, energy gels, coffee, and other caffeine-containing foods and beverages. It’s one of the most heavily-researched ergogenic (i.e., performance-enhancing) supplements in the world.
Caffeine can increase aerobic exercise performance between 2%–4% when 3–6 mg of caffeine per kilogram of body weight is consumed about 60 minutes before exercise. Performance improvements have been observed in cycling, running, swimming, skiing, and other endurance sports.[1]
A complete understanding of how caffeine exerts its ergogenic effects has yet to be established, but there is evidence to support several different mechanisms. Caffeine’s effects on the central nervous system primarily explain how it enhances performance. Caffeine blocks adenosine receptors in the brain, and in this way, may reduce pain perception, increase motivation, decrease perceived effort, and increase motor unit recruitment during exercise — all of which may contribute to improvements in aerobic exercise performance. Caffeine may also have direct effects on muscle contraction and force generation by increasing the availability and mobilization of calcium.[1]