Enhancing performance
Caffeine is a central nervous system stimulant that may reduce fatigue and drowsiness. At normal doses, caffeine has variable effects on learning and memory, but it generally improves reaction time, wakefulness, concentration, and motor coordination. The amount of caffeine needed to produce these effects varies from person to person, depending on body size and degree of tolerance.The desired effects arise approximately one hour after consumption, and the desired effects of a moderate dose usually subside after about three or four hours.
Caffeine can delay or prevent sleep and improves task performance during sleep deprivation.Shift workers who use caffeine make fewer mistakes that could result from drowsiness.
Caffeine in a dose dependent manner increases alertness in both fatigued and normal individuals.
A systematic review and meta-analysis from 2014 found that concurrent caffeine and l-theanine use has synergistic psychoactive effects that promote alertness, attention, and task switching;these effects are most pronounced during the first hour post-dose.
