Table 1 Summary of studies that explored the effects of caffeine on cognitive function
From: International society of sports nutrition position stand: caffeine and exercise performance
Author | Participants | Protocol | Outcome |
|---|---|---|---|
Sleep Deprived | |||
 Hogervorst et al. 2008 [82] | Well-trained cyclists (n = 24) | • Bar with 100 mg caffeine and 45.0 g CHO • Bar with only 45.0 g CHO • 300 mL non-caloric beverage | *↑Stroop and Rapid Visual Information Processing tests after 140 min and time to exhaustion exercise trial at 75% VO2max |
 McLellan et al. 2007 [334] | Soldiers (n = 20) | • 600 mg total caffeine in 200 mg does over 6 h period • Placebo | *↑ Increased vigilance |
 McLellan et al. 2005 [329] | Soldiers (n = 31) | • 200 mg caffeine (gum) mg doses over 5 h • Placebo | Maintained vigilance in control observation and reconnaissance vigilance task |
 McLellan et al. 2005 [330] | Soldiers (n = 30) | • 600 mg total caffeine in 100 mg and 200 mg doses over a 6 h period • Placebo | Sustained marksmanship vigilance and accuracy *less decrease in urban operations vigilance |
 Lieberman et al. 2002 [42] | U.S. Navy SEAL trainees (n = 68) | • 100 mg caffeine • 200 mg caffeine • 300 mg caffeine • Placebo | *↑improved vigilance and reaction time in both the 200 and 300 mg caffeine interventions following 72 h sleep deprivation |
 Kamimori et al. 2015 [332] | Special Forces Operators (n = 20) | • Four 200 mg doses of caffeine • Placebo | *maintained psychomotor speed, improved event detection, increased the number of correct responses to stimuli, and increased response speed during logical reasoning tests. ⬌Live-fire marksmanship was not altered by caffeine. |
 Tikuisis et al. 2004 [335] | Young Military Subjects (n = 20) | • 400 mg caffeine • 100 mg caffeine • 100 mg of caffeine • Placebo | *increased cognitive component of shooting task |
Not Sleep Deprived | |||
 Share et al. 2009 [336] | Elite male shooters (n = 7) | • 2 mg/kg caffeine • 4 mg/kg caffeine • Placebo | ⬌ shooting accuracy, reaction time, or target tracking time between groups |
 Pomportes et al. 2019 [337] | Modern pentathlon national team athletes (n = 10) | • Four counterbalanced sessions with: • 30 g CHO • 300 mg guarana complex • 200 mg caffeine • Placebo | * enhanced speed of information processing w CHO, and caffeine and guarana complex * lower RPE w caffeine and gaurana complex |
Younger males (n = 12) | • 5 mg/kg dose caffeine • Placebo 60 min before 30 s upper body Wingate anaerobic test | *Readiness to invest physical effort, and cognitive performance *Reduced rating of perceived exertion ⬌Response accuracy | |
Other Stressors | |||
 Share et al. 2009 [336] | Elite male shooters (n = 7) | • 2 mg/kg caffeine • 4 mg/kg caffeine • Placebo | ⬌ shoot accuracy, reaction time, or target tracking time between groups |
 Gillingham et al. 2004 [339] | Military reservists (n = 12) | • 5 mg/kg caffeine or placebo dosed before 2.5 h loaded march plus 1 h sandbag wall construction task then re-dose of 2.5 mg/kg caffeine or placebo | *↑ marksmanship performance (engagement time and number of shots fired) ⬌friend-foe discrimination |
 Zhang et al. 2014 [340] | Firefighters (n = 10) | • 400 mg caffeine • Menthol lozenges • Placebo | ⬌ Change in perceived exertion, mood reaction time, short-term memory, or retrieval memory |
 Crowe et al. 2006 [341] | Healthy subjects: male (n = 12) female (n = 5) | • 6 mg/kg caffeine • Placebo | ⬌ rating of perceived exertion |
 Foskett et al. 2009 [244] | Male soccer players (n = 12) | • 6 mg/kg of caffeine • Placebo | * Enhanced fine motor skills via improved ball passing accuracy and control |
 Stuart et al. 2005 [342] | Competitive male rugby (n = 9) | • 6 mg/kg caffeine • Placebo | *Increased ball-passing accuracy |
 Duvnjak-Zaknich et al. 2011 [343] | Moderately trained male athletes (n = 10) | • 6 mg/kg caffeine • Placebo | *Main effect for condition on decision time |