By Myriam Dagher
Licensed Dietitian, Public Health Nutrition MSc., Swimming Instructor

How many times have you walked into the gym room and overheard your sports-mates saying they had their cup of caffeine on their way to the gym before adding, “well, I am feeling much better now after that cup of caffeine!” Then, you would hear another mate whispering, “Who said that? This is a misconception… like most of the information in our community… Caffeine doesn’t do anything!” And you would feel puzzled, wondering what is actually true and whether caffeine does really affect your performance or not.

Caffeine has indeed been a controversially discussed substance for years. For a long time, it was categorized as doping. But as of 2004, restrictions on its consumption have been abolished (World Anti-Doping Agency, 2021). So, to be able to clearly understand its effects on performance, it is important to start knowing more about that substance in the first place!

What is Caffeine?
Caffeine is the world’s most consumed pharmacologic and psychoactive substance. It is found naturally in coffee beans, tea leaves, chocolate, cocoa beans, and cola nuts. The amount of caffeine varies greatly from a product to another; from 10 mg up to 100 mg per cup (240 mL). Caffeine, though having no nutritional value, has attracted the attention of many competitive and non-competitive athletes as a legal ergogenic aid.

What about caffeine and sports?

Research on the physiologic benefits of caffeine on sports performance is extensive in areas of strength, endurance, rates of perceived effort, hydration, and recovery.

The Australian Institute of Sports Nutrition (AIS) has classified the substance as an “A” level effective and safe supplement because a large number of systematic reviews and meta-analyses showed that caffeine intake can enhance performance at a dose of 1 to 3 mg per kilogram of body weight (mg/kg). The plateau in dose to performance appears to occur at 3 mg/kg (AIS, 2014). In other words, research using high doses of caffeine (6+ mg of caffeine/kg) indicates that lower doses can provide similar performance benefits with fewer negative side effects.

There is sound evidence that caffeine may enhance the performance of endurance sports (lasting more than 60 min), sustained high-intensity sports (1 to 60 min), and intermittent sports (Salinero & Del Coso, 2019). However, its effect is still unclear in low-intensity exercises and in single-strength or power efforts, in which the effects appear to be small and limited to certain muscle groups (Grgic et al., 2018).

Now, what are the pathways by which caffeine enhances performance in the aforementioned types of sports? Apparently, caffeine contributes to endurance performance due to its ability to enhances mobilization of fatty acids and thus conserve glycogen stores in muscles. Also, it directly affects muscle contractility, possibly by facilitating calcium transport. It could reduce fatigue as well by reducing plasma potassium accumulation (Mahan & Raymond, 2017).

The energy-enhancing effect is seen with up to 3 mg of caffeine per kg of body weight (Spriet, 2014). For example, for a 68 kg athlete, this is about 200 milligrams of caffeine (e.g. 3.5 rounded teaspoons of instant coffee). The following table lists the caffeine amounts in some common drinks. Is more caffeine the better? In fact, over-consuming caffeine may lead to unwanted side effects, such as headaches, insomnia, reflux, shakiness, heart palpitations, and increased urination; and thus limit performance.

Consumer demand for caffeine has resulted in greater accessibility and acceptance of a variety of beverages beyond coffee and tea. An emerging trend in sports nutrition is the intake of caffeine-containing energy drinks and shots for performance. Unfortunately, these products may contain a higher dosage than what is required, so make sure to read the nutrition label first before picking your favorite product!

What's the caffeine content in common beverages?

How much is enough?

The vast majority of studies conclude that caffeine taken an hour before exercise does indeed enhance performance and makes the effort seem easier (by about 10 percent – so do not overestimate its effect!) (Mahan & Raymond, 2017). Athletes also need to work with their professionals in sports to determine the most beneficial timing protocol, which may include taking caffeine (e.g. before or during competition, before and throughout competition) (AIS, 2014).

Although a cup or two of coffee before exercise may be a helpful energizer, more may be of little value. So, if you are tempted to jazz yourself up with a second mugful, think again. You may find that the second mug will do you in with the caffeine jitters.

Because each person responds differently to caffeine, do not assume that you will perform better with a caffeine boost. You might just end up nauseated, coping with a “coffee stomach,” or feeling agitated at a time when you are already nervous and anxious. And be cautioned: although a morning cup of coffee can assist with a desirable bowel movement, a pre-competition mugful might lead to transit troubles. Experiment during training to determine whether caffeinated beverage or plain water is the better bet (Clark et al., 1995).
Be sure no trouble is brewing in your desire for caffeine!

References and Additional Reading
Australian Institute of Sport (AIS). 2014. Supplements: Executive Summary.
Clark, N. (1990). Nancy Clark’s sports nutrition guidebook. Clinical Nutrition Insight, 16(8), 6.

Grgic, J., Trexler, E. T., Lazinica, B., & Pedisic, Z. (2018). Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis. Journal of the International Society of Sports Nutrition, 15(1), 1-10.

Mahan L. K., Raymond, J. L. (2017). Krause’s Food & the Nutrition Care Process. Fourteenth Edition. L. Kathleen Mahan, Janice L. Raymond.

Salinero, J. J., Lara, B., & Del Coso, J. (2019). Effects of acute ingestion of caffeine on team sports performance: A systematic review and meta-analysis. Research in Sports Medicine, 27(2), 238-256.

Southward, K., Rutherfurd-Markwick, K. J., & Ali, A. (2018). The effect of acute caffeine ingestion on endurance performance: a systematic review and meta–analysis. Sports Medicine, 48(8), 1913-1928.

Spriet, L. L. (2014). Exercise and sport performance with low doses of caffeine. Sports Medicine, 44(2), 175-184.

World Anti-Doping Agency. (2021). The 2021 Monitoring Program. Retrieved from https://www.wada-ama.org/en/resources/science-medicine/monitoring-program