Caffeine is consumed by over 80% of U.S. adults. This review examines the effects
caffeine has on cognitive and physical function, since most real-world activities
require complex decision making, motor processing and movement. Caffeine exerts its
effects by blocking adenosine receptors. Following low (∼40mg or ∼0.5mgkg(-1)) to
moderate (∼300mg or 4mgkg(-1)) caffeine doses, alertness, vigilance, attention, reaction
time and attention improve, but less consistent effects are observed on memory and
higher-order executive function, such as judgment and decision making. Effects on
physical performance on a vast array of physical performance metrics such as time-to-exhaustion,
time-trial, muscle strength and endurance, and high-intensity sprints typical of team
sports are evident following doses that exceed about 200mg (∼3mgkg(-1)). Many occupations,
including military, first responders, transport workers and factory shift workers,
require optimal physical and cognitive function to ensure success, workplace safety
and productivity. In these circumstances, that may include restricted sleep, repeated
administration of caffeine is an effective strategy to maintain physical and cognitive
capabilities.