Caffeine and performance in endurance (aerobic) exercise
A 2009 review paper focused on endurance performance lasting more than five minutes and measured the time it took to run, cycle or row a set distance, rather than time to exhaustion, which better reflects typical competition conditions. Inclusion criteria were met by 21 papers covering 33 trials3. Thirty of these showed a performance improvement with a mean improvement of 3.2 ± 4.3 % with caffeine consumption. The review concluded that overall caffeine ingestion can be an effective ergogenic aid for endurance athletes when consumed in moderate quantities (3-6mg/kg body weight), before and/or during exercise3. However, abstaining from caffeine for at least 7 days before an event optimised caffeine’s ergogenic effect on performance during the event3.
In 2011, a study examining caffeine withdrawal and high-intensity endurance cycling performance also suggested that an intake of caffeine of 3mg/kg body significantly improved exercise performance irrespective of whether a 4-day withdrawal period was imposed on habitual caffeine users4. Further research published in 2012 concluded that a caffeine intake of 3mg/kg body weight appears to improve cycling performance; although doubling this to (6mg/kg body weight) did not confer additional performance improvement in well-trained athletes5.
Additionally, a 2013 study considered the potentially enhancing effects of caffeine versus coffee, concluding that caffeine consumed in coffee (5mg/kg body weight) and as a supplement (5mg/kg body weight) one hour prior to exercise can improve endurance exercise performance6.
A 2016 review concluded that there is an indication that the use of coffee (as opposed to caffeine alone) as an ergogenic aid can improve performance in endurance cycling and running7. The authors suggested that coffee providing 3-8.1 mg/kg of caffeine may be used as a safe alternative to anhydrous caffeine to improve endurance performance7.
Additionally, results from a 2017 study of male runners suggest that 60 minutes after ingesting 0.09 g/kg of caffeinated coffee, one-mile race performance was enhanced by 1.9% and 1.3% compared with a placebo and decaffeinated coffee respectively, in trained male runners8.
A 2017 meta-analysis suggested that caffeine had a suppressive effect on ratings of perceived exertion, and had no effect on measures of heart rate, respiratory exchange ratio or V̇O29. The authors suggested that whilst the positive effects of caffeine supplementation on sustained high-intensity exercise performance are well accepted, the mechanisms to explain that response remain unresolved9.
A small number of studies have considered a potential ergogenic effect of low and very low intakes of caffeine taken late in prolonged exercise. A low intake of caffeine (~200 mg) has been shown to improve vigilance, alertness and mood, and improve cognitive processes during and following strenuous exercise, however there is a lack of research on its potential effects on high intensity sprint and burst activities. As the response to caffeine consumption is variable, athletes need to determine whether the ingestion of lower amounts of caffeine before and/or during training and competitions is ergogenic on an individual basis10.
Caffeine and muscle pain
In 2009 a research paper reported on the effects caffeine had on muscle pain during 30 minutes of high-intensity cycling. Caffeine ingestion (5mg/kg body weight) was statistically significant in reducing the reported intensity of muscle pain and the effect was larger in the group of habitually low caffeine consumers11.
A 2011 study examined the effect of caffeine on leg pain and rating of perceived exertion during repeated bouts of high intensity exercise. Data revealed no effect of caffeine on leg pain or perceived exertion although caffeine intake improved multiple measures of performance. The authors concluded that it was plausible to suggest that subjects were able to perform better with similar levels of pain and exertion with 5mg/kg of caffeine compared to a placebo12.