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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
 Duncan et al. 2019 [228, 338] 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
  1. Outcomes are bold caffeine group specific; * = significant difference, ↑ = improved performance, ⬌ no change, mg/kg = milligram per kilogram, CHO = carbohydrate