[Jarod Connell graduated from NC State University with a degree in Human Biology and a minor in Sports Science. He is certified as a NASM-CPT and is taking part in the Athletic Lab Coaching Mentorship program.]

Caffeine has long been used as an ergogenic aid in sports. How much do we really know about it or how much it helps us? Caffeine has been used in sports since the early 1900s due to its perceived ability to stimulate muscle and overcome mental fatigue (17). However, it wasn’t until the 1940s that notable research began to appear (17). In this blog, we’ll explore what caffeine does within our bodies and how it impacts sports performance.

What does caffeine do in our body?

Caffeine is shown to inhibit adenosine receptors and mostly targets the A1 and A2 adenosine receptors. This leads to increases in pain suppression, firing rates of motor units, and neurotransmitter release (1). Adenosine is shown to decrease some Central Nervous System (CNS) neurotransmitters, including dopamine, serotonin, acetylcholine, glutamate, and norepinephrine. This means adenosine slows down our neural activity and makes us sleepy (22). Because caffeine’s chemical structure resembles adenosine it inhibits adenosine from binding and binds to the receptors itself, increasing the concentration of these neurotransmitters, and thereby actually increasing neural activity and alertness (1).

Caffeine was previously believed to increase lipolysis, the breakdown of fats for energy, saving our muscle glycogen from being used, and release of calcium from our intracellular stores. However, a study in 2010 by Davis and Green reported that a standard dose of caffeine doesn’t indicate that these mechanisms play a large role (14). This lines up with what was found in the Institute of Medicine article which reports that concentrations in the body for behavioral effects are too small to be significant for phosphodiesterase inhibition. For calcium mobilization, the in-lab concentration to observe the effect is much higher than the concentration required in the body so it is “probably physiologically irrelevant” (16).

Endurance

The largest area of study for caffeine use has been aerobic exercise and it is also the area that has consistently shown improvement of endurance. Studies have shown endurance improvements of 2-4% when using caffeine doses of 3-6 mg/kg (1). These endurance sports included swimming, running, cross country skiing, and cycling.

Studies conducted on swimmers measured several tests, including: a max handgrip test, a 45-second swim on a swim ergometer, a simulated 50 meter competition, and a countermovement jump (3). The caffeinated swimmers drank energy drinks of 3 mg/kg and showed improvements in every test; however, no tests of longer distances were performed.

The effect of caffeine on cross country skiing performance has been investigated with sub elite skiers performing a 8 km double pole time trial and a time until task failure using 90% of double pole VO2max. The caffeinated skiers, compared to the placebo group, improved in the time to task failure and had improved velocity the first 4 km of the 8 km time trial, but did not show significant time improval overall in the 8 km time trial. Additionally, the caffeinated skiers described lower rates of perceived exertion (RPE) and decreased muscle pain in their arms (2).
Running has a bit more research, but while caffeine does seem to help in longer distances, results for sprinting are a bit more unclear. In a study by Prins et al. they tested the 5 km times of “recreational endurance runners” (4). The caffeinated runners showed an improvement in their time trials compared to the placebo group but reported no difference in RPE.

Cycling used two different caffeine dosages along with their placebo group. One group consumed 3 mg per kg of bodyweight and the other 6 mg per kg. They were tested on 75% of their peak sustainable power for 60 minutes. Both groups showed statistically significant improvements compared to the placebo with the 3mg/kg group resulting in a 4.2% increase and the 6 mg/kg at a 2.9% increase (5). Desbrow et al. also mentions that there was no statistically significant difference between the two doses and upping dosage to 6 mg/kg does not seem to result in any added improvement (5).

Strength, Power and Muscular Endurance

Does caffeine help me when I’m lifting in the gym? I’m not a big drinker of caffeine, but I know I’ve wondered this question before when I’ve seen others downing energy drinks as they pull into the gym parking lot.

Caffeine has been shown to increase strength in both lower body and upper body exercises, with the greatest improvements occurring in the knee extensors (6,7,8). The improvements in these studies ranged from 2 to 7% and would likely have the greatest effect on athletes who compete in strength-based sports like weightlifting and powerlifting (1).

Power is most often measured in the caffeine research literature by using the Wingate cycling test (a 30-second maximal effort sprint on a cycle ergometer). Jozo Grgic et al. did a meta analysis and found that mean power increased by 3% and peak power increased by 4% (23). Sprint performance can be increased by caffeine after a 90 second rest interval; there was no benefit from repeated sprints with a 20 second interval (19). While this is performed on a cycling test, it’s a measure of power. If you’re training for power, take your rest. Intermittent sprinting and single sprint performance’s are most backed by the research while repeated sprints are inconsistent.

Caffeine doesn’t affect everyone the same way, and studies show variable results within participants. A study from 2015, including 20 cyclists, showed that 13 of the 20 did improve performance. The other seven; however, either did not alter or worsened (1, 20). Another study from 2005, with 18 male athletes, found that caffeine did not improve performance in four of the athletes (1, 21).

Delaying muscular fatigue is possible with the use of caffeine, but isn’t always consistent (1). Caffeine has also been found to enhance jumping and throwing performances. Increases of 2-4% have been observed in vertical jump performance, both for single jumps and repeated jumps (1). A study of 9 collegiate throwers found that caffeine did increase max shot put throw distance (15). Two meta analyses reported that caffeine was ergogenic for muscular endurance showing a percent change of 6 to 7% (1). However, other studies have shown that there might be no improvements, and a study by Wilk et al. even observed impairments in some individuals (9).

Specific sports

CARY, NC – MAY 22: Denise O’Sullivan #8 of the North Carolina Courage brings the ball up the field during a game between Orlando Pride and North Carolina Courage at Sahlen’s Stadium at WakeMed Soccer Park on May 22, 2021 in Cary, North Carolina.

Caffeine has been tested for specific sports by using sport simulation matches and has been reported by athletes to help with sport tasks in team and individual sports. In a study of 20 experienced basketball players, it was found that caffeine increased mean jump height and during a simulated game, increased number of body impacts and performance index rating (PIR) (18). Performance index rating takes into account all statistics, i.e. point, rebounds, missed field goals, turnovers, etc.

In soccer players, caffeine has been found to increase repeat-sprint ability (RSA), total distance covered, jump height, and pass accuracy (10,11). However, caffeine did not improve the agility T-test in female soccer players (1).

Two different studies have been performed with volleyball players, one being with female volleyball players and the other with male volleyball players. Both studies found that caffeine helped to improve jump height, decreased time to complete an agility test, and successful volleyball actions were performed more frequently (12,13).

Just because more sports are not listed, isn’t to say caffeine doesn’t help in other sports. It has shown performance improvements in running pace in rugby or physicality in rugby and ice hockey (1). The list goes on, but that doesn’t mean that it will help with everything you might think it will or want it to. As caffeine hasn’t been found to aid performance in NFL combine anaerobic tests or agility in rugby (1). Studies have varied on the results found, but caffeine is “on average” ergogenic for many sports related tasks (1).

Caffeine and cognitive performance

The majority of studies have shown that caffeine can enhance cognitive performance and fine motor skills. This was represented by the study discussed previously in which soccer players experienced improvements in pass accuracy and control (11). Sports are not the only studies that have been performed and shown results. As caffeine has also been used in special forces on running and marksmanship tests where sleep became less frequent. It showed improvements in vigilance and reaction time (1). This just goes to show the important role that caffeine can have on our cognitive function.

Considerations

Caffeine consumed in the range of 3 to 6 mg/kg were shown to improve exercise performance. While high doses like 9 mg/kg are not backed heavily to get an ergogenic response and have more prevalence of side effects (1). The timing most often used was 60 minutes prior to any exercise. This time constraint can depend on the source from which you are getting the caffeine, i.e. caffeine pill, energy drink, chewing gum.
Athletes may need to watch their caffeine doses if competing. Though no longer considered a controlled substance by WADA (World Anti-Doping Agency), caffeine IS considered a banned substance by the NCAA if over 15 µg/mL. This converts to an intake greater than 10 mg/kg, which is more than 3x the effective dosages and has a high prevalence of side effects (1).

Side-effects

What are the side-effects of caffeine, you might ask? Some of the most commonly experienced side-effects are headaches, insomnia (inhibited sleep quality), anxiety, tachycardia (a fast beating heart), or even dehydration(1). The side-effects increase as you increase the dosage of caffeine ingested. The smaller the dosage, the fewer side-effects (1).

Conclusion

Caffeine is not supposed to replace all other qualities that help our bodies function in these scenarios. You still need to sleep, eat, and hydrate appropriately. This is why it is called an ergogenic aid as it should AID performance. Does this mean that you have to stop taking caffeine? No. Does it mean that you should start taking it? No. The answer to the title of this blog is that you need to assess yourself with caffeine to find if caffeine actually helps your performance or if it hinders you. While research shows that it can have ergogenic effects on several aspects, it is all individualized.

Sources

  1. Guest, N.S., VanDusseldorp, T.A., Nelson, M.T. et al. International society of sports nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr 18, 1 (2021). https://doi.org/10.1186/s12970-020-00383-4
  2. Stadheim, H. K., et al. “Caffeine Improves Performance in Double Poling during Acute Exposure to 2,000-M Altitude.” Journal of Applied Physiology, vol. 119, no. 12, Dec. 2015, p. 1501–1509, https://journals.physiology.org/doi/full/10.1152/japplphysiol.00509.2015.
  3. Lara, Beatriz et al. “Acute consumption of a caffeinated energy drink enhances aspects of performance in sprint swimmers.” The British journal of nutrition vol. 114,6 (2015): 908-14. doi:10.1017/S0007114515002573
  4. Prins, Philip J et al. “Energy Drinks Improve Five-Kilometer Running Performance in Recreational Endurance Runners.” Journal of strength and conditioning research vol. 30,11 (2016): 2979-2990. doi:10.1519/JSC.0000000000001391
  5. Desbrow, Ben et al. “The effects of different doses of caffeine on endurance cycling time trial performance.” Journal of sports sciences vol. 30,2 (2012): 115-20. doi:10.1080/02640414.2011.632431
  6. Warren, Gordon L et al. “Effect of caffeine ingestion on muscular strength and endurance: a meta-analysis.” Medicine and science in sports and exercise vol. 42,7 (2010): 1375-87. doi:10.1249/MSS.0b013e3181cabbd8
  7. Grgic, Jozo, and Craig Pickering. “The effects of caffeine ingestion on isokinetic muscular strength: A meta-analysis.” Journal of science and medicine in sport vol. 22,3 (2019): 353-360. doi:10.1016/j.jsams.2018.08.016
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  9. Wilk, Michal et al. “The Effects of High Doses of Caffeine on Maximal Strength and Muscular Endurance in Athletes Habituated to Caffeine.” Nutrients vol. 11,8 1912. 15 Aug. 2019, doi:10.3390/nu11081912
  10. Del Coso, Juan et al. “Effects of a caffeine-containing energy drink on simulated soccer performance.” PloS one vol. 7,2 (2012): e31380. doi:10.1371/journal.pone.0031380
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