Research suggests that caffeine can have benefits in some short-term, high-intensity exercises and under certain conditions15-17.
A 2009 review looking at the effects of caffeine on anaerobic exercise performance considered 29 studies, finding that 17 of the studies revealed caffeine to have a significant effect16. It was also observed that there was significant variation between the studies. Several factors in the various studies were highlighted as potential explanations for the variation: trained vs. untrained participants, caffeine-habituated vs. non-habituated participants, slow vs. fast caffeine-metabolizers amongst the participants, different dosing regimens (fixed amount of caffeine vs. mg per kg body weight), as well as different types of tests.
Results of a 2017 meta-analysis indicated a significant difference between the placebo and caffeine trials on mean power output and peak power output on a cycle ergometer. This meta-analysis adds to the current body of research that suggests that caffeine ingestion can enhance components of anaerobic performance17.
A 2019 systematic review of caffeine supplementation and physical performance, muscle damage and perception of fatigue in soccer players concluded that a single dose of caffeine, ingested 5-60 min before a soccer practice, might produce valuable improvements in certain abilities related to enhanced soccer physical performance. The authors also suggested that caffeine does not seem to cause increased markers of muscle damage or changes in perceived exertion during soccer practice18. However, a further systematic review and meta-analysis of the effects of caffeine supplementation on physical performance of soccer players in relation to anaerobic power, did not find any significant improvement in soccer-related performance with caffeine compared with placebo or no intervention19.
The overall results suggest that caffeine can have benefits in some short-term, high-intensity exercises particularly under certain conditions, such as trained athletes who had abstained from caffeine before power-based sports and team sports events following ingestion of a moderate amount of caffeine15-19.
Professional society position on caffeine
The International Society of Sports Nutrition position on caffeine intake concludes that supplementation with caffeine has been shown to enhance various aspects of exercise performance in many but not all studies. They suggest that small to moderate benefits of caffeine use include muscular endurance, movement velocity and muscular strength, sprinting, jumping, and throwing performance, as well as a wide range of aerobic and anaerobic sport-specific actions40.
Summary of meta-analyses
Caffeine and carbohydrates
A 2010 paper looked at the effect of caffeine (3.7mg/kg body weight) in addition to a carbohydrate-electrolyte supplement in a simulated football performance20. The authors found that the caffeine group better maintained, and improved, short distance sprinting and jumping performances, compared to the no-caffeine group20. A 2011 review of the research suggests that the ingestion of carbohydrates with caffeine provides a significant but small improvement in endurance performance compared with carbohydrates alone21. However, the magnitude of the performance benefit that caffeine provides was less when added to carbohydrate than when added to placebo21.
Short-term effects of caffeine
A 2010 paper22 reported that caffeine intake of 6mg/kg body weight in trained women resulted in an improvement in an “all at once” test but not in a repeated test22.
A further paper23 tested two different caffeine intakes (2mg/kg body weight and 5mg/kg body weight) in active participants23. The ingestion of the higher caffeine amount, but not the lower, resulted in an improvement in knee extension/flexion exercise performance. This effect disappeared in the second bout, meaning any benefits of caffeine were short-term only23.
