Table 5.

Details and results of the studies reviewed investigating the effect of acute caffeine supplementation compared to a placebo on objective measures of cognitive performance.

Study	Population	Intervention	Outcomes Analyzed	Main Results vs. Placebo
Russell et al. [52]	14 male professional academy rugby players (18 ± 1 years)	4.1 ± 0.5 mg/kg of caffeine (gum) 15 min before and during exercise	SRT test Stroop test	SRT Congruent response accuracy Incongruent response accuracy
Duncan et al. [51]	12 male subjects accustomed to regular high-intensity exercise (21.4 ± 4.4 years)	5 mg/kg of caffeine (capsules) 60 min before start	Modified flanker task	↓ Congruent RT ↓ Incongruent RT Congruent response accuracy Incongruent response accuracy
Bello et al. [39]	12 male (21.8 ± 2.53) and 15 female (19.65 ± 3.62) professional soccer players	275 mg (≈3.69 mg/kg) caffeine capsule 30 min before start	SRT test Go/no-go Go/no-go and COGRT wrong	↑ SRT CRT CRT score COGRT COGRT score COGRT wrong answer
Pomportes et al. [49]	16 male and six female recreational cyclists (26 ± 8) years	67 mg/25 mL (≈0.93 mg/kg) of caffeine + 7% carbohydrate mouthwash Immediately before start and every 13 min during exercise	Duration-production task Simon task	↓ Produced duration ↓ Variance ↑ Congruent mean RT ↓ Incongruent mean RT Error rate (%)
Ali et al. [33]	10 female team game players from recreational to international (24 ± 4 years)	6 mg/kg caffeine capsule 60 min before start	CRT test Stroop test	CRT RT CRT accuracy ‡ Stroop test RT † Stroop test accuracy
Church et al. [47]	10 male recreationally active subjects (25.5 ± 1.8 years)	3 mg/kg caffeine drink 60 min before start	Reaction time test Multiple object tracking	Upper body RT Lower body RT Multiple object tracking
Share et al. [53]	Seven male elite clay target shooters (28.4 ± 9.4 years)	2 or 4 mg/kg caffeine tablets 60 min before start	Reaction time test Tracking time of target	RT TT1 TT2
Hogervorst et al. [38]	24 well-trained male subjects (23 ± 5 years)	100 mg (≈1.36 mg/kg) of caffeine + 45 g carbohydrate energy bar Immediately before and every 55 min during exercise	Stroop Color and Word test RVIP test Visual search test Word learning Test	↓ Stroop RT Stroop accuracy ↓ RVIP RT ↑ RVIP PT rate ↓ RVIP miss rate ↓ Visual Search RT ↑ Visual Search accuracy Delayed recall words
Crowe et al. [46]	12 male and five female team sports players (21.1 ± 3.0 years)	6 mg/kg caffeine drink 90 min before start	Simple visual reaction time test Number recall test	RT Number recall
Hogervorst et al. [37]	15 male professional cyclists or triathletes (23.3 ± 3.6 years)	8 mL/kg of 150, 225, or 320 mg/l of caffeine + 68.8 mg/l carbohydrate solution (≈1.2, 1.8, or 2.56 mg/kg of caffeine) 60 min before start 3 mL/kg of 150, 225, or 320 mg/l of caffeine + 68.8 mg/l carbohydrate solution (≈0.45, 0.675, or 0.96 mg/kg of caffeine) every 20 min during exercise	Stroop Color and Word Test SDT test Motor choice reaction time test VVLT	↑ Stroop speed ↑ SDT efficiency ↑ SDT speed ↑ Simple psychomotor speed ↑ Complex psychomotor speed ↑ S-R incompatible choice speed VVLT delayed number recall ↑ VVLT speed

↑ Statistically significant increase; ↓ statistically significant decrease; † increasing tendency; ‡ decreasing tendency. Without any marks indicates that there were no differences between caffeine and the placebo for the measures. RT: reaction time; SRT: simple reaction time; CRT: choice reaction time; COGRT: cognitive load reaction time; RVIP: rapid visual information processing; SDT: signal detection test; VVLT: visual verbal learning test.