Caffeine is a known ergogenic (i.e. performance-enhancing) substance used by many athletes participating in various disciplines. But does it work for all types of exercise? What are the mechanisms behind caffeine and performance? How does it impact health?
Caffeine as a supplement
Caffeine is an alkaloid present in plants such as coffee that acts as an stimulant. The form commonly used as a sports supplement is called anhydrous caffeine and comes in various presentations, including pills, powders, gums, gels and liquids. It can also be consumed in the form of coffee or tea, although this makes it difficult to figure the exact amount of the active compound.
Researchers have consistently found a positive relationship between caffeine and performance in endurance sports. The generally recommended dose is 3-6 mg caffeine/kg bodyweight taken 60 minutes before exercise (1, 2). In addition, athletes may also utilise lower doses taken before and during the event (2).
Strength and power
A systematic review including 10 studies assessing the effect of caffeine and performance in strength and power exercises. The number of participants per study was small and the majority of subjects were male. The researchers found that caffeine improved upper body (but not lower body) strength and muscle power as measured by vertical jumps (3).
A study with 54 trained young men examined the effect of 300 mg of caffeine anhydrous, the equivalent dose from coffee or placebo on strength exercises. They were tested on one-rep max and repetitions to fatigue of leg press and bench press. There was no difference between the groups (1). The same study also tested participants on a bike sprint test. Average total work was higher for participants who consumed caffeine in either form (1).
Mechanisms behind caffeine and performance
Caffeine’s ergogenic effects might be exerted by effects on adenosine receptors in which it acts as an antagonist, reduced pain/effort perception (1, 2, 3), release of endorphins, increased alertness (2) and improvements in neuromuscular function – including motor unit recruitment (2, 3).
Chemical structure of caffeine (3)
Excessive consumption of caffeine can produce negative side effects, such as nausea, anxiousness and insomnia. This may happen with doses equal or higher to 9 mg/kg bodyweight. In addition, these doses do not seem to provide extra performance benefits (2).
It is also thought that caffeine produces excessive diuresis (urine production), subsequently causing dehydration. A meta-analysis of 16 studies involving 379 participants found that caffeine intake does not produce excess diuresis to the level that could be detrimental to an athlete. This could only be a problem in multi-day events (5).
Finally, it’s important to note that a great amount of caffeinated pre-workout supplements also contain other substances, some of them banned, that could negatively impact health. When in doubt, consult with a sports dietitian, particularly if you compete on regulated sports. If you are not an elite/professional athlete, you can try consuming coffee or tea instead. You can find more about the nutrition and health effects of coffee in this post).
- Trexler ET, Smith-Ryan AE, Roelofs EJ, Hirsch KR, Mock MG. Effects of coffee and caffeine anhydrous on strength and sprint performance. European journal of sport science. 2016;16(6):702-10.
- Peeling P, Binnie MJ, Goods PSR, Sim M, Burke LM. Evidence-Based Supplements for the Enhancement of Athletic Performance. International Journal of Sport Nutrition and Exercise Metabolism. 2018;28(2):178-87.
- Grgic J, Trexler ET, Lazinica B, Pedisic Z. Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis. Journal of the International Society of Sports Nutrition. 2018;15:11.
- National Center for Biotechnology Information. PubChem Compound Database; CID=2519, https://pubchem.ncbi.nlm.nih.gov/compound/2519 (accessed Oct. 12, 2018).
- Zhang Y, Coca A, Casa DH, Antonio J, Green JM, Bishop PA. Caffeine and diuresis during rest and exercise: A meta-analysis. J Sci Med Sport. 2015 September; 18(5): 569–574.