There is a large literature that has examined the use of caffeine for maintaining vigilance, alertness, mood, executive control, and related parameters. This research often investigates situations where maintaining vigilance and performance is critical, as in the military and other professions where people are awake for long periods of time. Lieberman and colleagues have worked in this area for many years and published many papers on the potential usefulness of caffeine. For example, they gave 20 subjects four random doses of caffeine (32, 64, 128 and 256 mg) and assessed auditory vigilance and reaction time and mood in healthy volunteers [
49]. All four caffeine doses improved the performance of these tests. More recent work indicated that the optimal dose of caffeine is ~200 mg when vigilance, mood, alerting, orienting, and executive control were assessed against other caffeine doses or no caffeine [
50,
51]. The plateauing of beneficial effects at ~200 mg of caffeine is believed to match the adenosine-mediated effects on dopamine-rich areas in the human brain and their involvement in the executive control of visual attention and alerting [
49]. Hogervorst et al. [
52,
53] published two studies suggesting that low doses of caffeine improve cognitive performance during and after strenuous exercise. The first study had trained cyclists/triathletes complete an all-out 1 h cycling time trial on five occasions. They randomly received a water placebo, a CES placebo, or one of three CESs with either, 150, 225 or 320 mg of caffeine before and during the cycle [
52]. Cognitive tests, including memory, psychomotor and attention tasks, were carried out before and immediately after the time trial. The two low doses of caffeine improved all cognitive functions following exercise and the higher dose provided no further improvement. These results clearly demonstrated that the ability to concentrate and make decisions was improved by caffeine immediately after exhausting exercise, leading to the suggestion that this effect would also be present in the later stages of exercise [
52]. A second study directly measured the effects of ingesting 100 mg of caffeine in an energy bar (with 45 g CHO) before exercise and again at 45 and 115 min of a 3 h cycle at 60 %
VO
2max, followed by a time-to-exhaustion trial at 75 %
VO
2max on cognitive function measures [
53]. A second trial gave the energy bar only, and a third was a placebo trial with an energy- and caffeine-free beverage. Cognitive function tests (Stroop test and rapid visual information processing tests) were administered before exercise and after 70 and 140 min of the trial and 5 min after the trial. Performance was best following caffeine ingestion (total of 300 mg before and during exercise) on the complex information processing tests, especially after 140 min of cycling. Cycle-ride time to exhaustion was also the longest in the caffeine trial. These results suggest that low-dose caffeine ingestion during prolonged exercise helps with decision making and could be useful for all sports where critical decision making is important for success late in an event or game [
53].