Key points
- Caffeine improves both endurance and strength/power performance
- ‘Coffee’ and caffeine are not always interchangeable due to the myriad chemicals in coffee that can affect people differently
- The anaerobic benefits of caffeine are higher in men than women
- Caffeine improves fat-loss in a dose-dependent fashion
- Caffeine dosages typically used in research are likely to be too high for regular or sustained use for many people
Caffeine, along with creatine, is perhaps the most commonly used, most effective, and most studied performance-enhancing supplement.
Around 3-9 mg/kg of caffeine improves performance in both resistance and endurance activities,1-5 and for muscular endurance, there are benefits irrespective of muscle size, location, the form of intake, or dosage.6
Caffeine for endurance and conditioning
Caffeine reliably improves performance in a ‘Yo yo’ test.7 This suggests that there might be a greater benefit to ‘conditioning’ type exercise with little to no rest between exertions, and/or those activities with more constant pacing. This idea is also supported by another review which demonstrated that caffeine supplementation did not improve power or maximum running distance but did improve performance in time-trials (at a dose of 6 mg/kg),8 and another which showed the effects from caffeine are increased with the duration of an event.9
Caffeine is also effective for improving rowing performance. In a review including 7 trials, improvements of around 4 seconds were seen in the 2000 m row (with around 6W increase in power). No significant differences between caffeine and placebo were found for perceived exertion, oxygen consumption, respiratory exchange ratio, or heart rate.
Caffeine and sports performance
In complex sports, (like soccer) caffeine is also likely to improve power and repeatable power, speed and sprint repeat performance, and total endurance capacity.10, 11
Caffeine for strength, power, and strength-endurance
Interestingly, in a review of studies looking at the effects of caffeine on performance in either the bench press or leg press, caffeine improved strength-endurance[1] and maximal strength[2] in the bench press but did not improve perceived exertion. In the leg press, no significant improvement was observed in muscular endurance, strength, or perceived exertion.12
For resistance movements, caffeine also increases the velocity at all loads (and for both mean and peak velocity), and for both upper and lower body movements.13
[1] WMD 0.87 (95% confidence interval (CI): 0.33, 1.41; repetitions, p = 0.001; 15 studies)
[2] WMD 2.01 (95% CI: 0.20, 3.80 kg; p = 0.02; 7 studies)
Caffeine ≠ coffee
Coffee and caffeine are often considered interchangeably, but there might be different effects from these because of the large array of phytochemicals in coffee and other caffeine-containing natural beverages. There can also be adverse effects from coffee, for some people, from coffee that is not related to caffeine.
Energy drinks
Energy drinks typically contain relatively high caffeine doses (~300 mg+). In a review of the effects of caffeine-containing energy drinks, they were found to improve endurance and jump performance but these results were not dependent on the dose of caffeine but conversely were improved increased taurine dosage.14
Sex differences
Caffeine produces similar performance benefits in men and women but the ability of caffeine to improve power, total weight lifted, and to improve sprint performance is greater in men. So, it is likely that the anaerobic benefits of caffeine are greater in men than women.15
Fat loss
Caffeine has small effects on macronutrient metabolism that are unlikely to be meaningful. There are minor, transient increases in insulin resistance and reduced glucose disposal,16 but this is married to reduced adipose tissue deposition (reduced fat storage) and increased fat utilisation (leading to increased fat-loss).17
A systematic review of the effects of caffeine on weight and fat loss showed a linear effect of caffeine on fat-loss (i.e. the more was taken; the more fat was lost.) Studies have used dosages from 60 to 4000 mg per day with a median of 360 mg per day (approximately 3 cups of coffee). Those consuming 2 mg/kg per day lost 28% more fat than those consuming 1 mg/kg.18 Along with increased metabolic rate and fat utilisation, caffeine also suppresses appetite when taken less than 3 hours before a meal.19
Note: Green tea has been posited to have additional effects over and above its caffeine content. While there may be health benefits from the various plant chemicals in green tea, a review of the evidence suggests that the fat-loss benefits resulting from green tea are due to caffeine.20
For most people, coffee is safe and offers significant benefits to health
A note about dosing
The doses used in many studies are very high. For example for me, at a bodyweight of 85-90 Kg, I would be expected to take between 200 and 800 mg of caffeine before an event; the equivalent of 2 to 8 cups of coffee!
Clinically, we find that those types of doses are unsustainable and there is a wide variation in personal responses. My advice is to start with a cup of coffee or tea and titrate the dose up by one cup per session, all the while gauging your performance, how you feel, and most importantly, whether you experience any adverse effects such as jitters, anxiety, energy crashes, or impaired sleep length of quality.
Find a dose that works for you.
References
1. Fatolahi H, Farahmand A, Rezakhani S. The Effect of Caffeine on Health and Exercise Performance with a Cold Brew Coffee Approach: A Scoping Review. Nutrition and Food Sciences Research. 2020;7(2):1-12.
2. Astorino TA, Roberson DW. Efficacy of Acute Caffeine Ingestion for Short-term High-Intensity Exercise Performance: A Systematic Review. The Journal of Strength & Conditioning Research. 2010;24(1):257-65.
3. Grgic J, Mikulic P, Schoenfeld BJ, Bishop DJ, Pedisic Z. The Influence of Caffeine Supplementation on Resistance Exercise: A Review. Sports Medicine. 2019;49(1):17-30.
4. Southward K, Rutherfurd-Markwick KJ, Ali A. The Effect of Acute Caffeine Ingestion on Endurance Performance: A Systematic Review and Meta–Analysis. Sports Medicine. 2018;48(8):1913-28.
5. Grgic J, Grgic I, Pickering C, Schoenfeld BJ, Bishop DJ, Pedisic Z. Wake up and smell the coffee: caffeine supplementation and exercise performance—an umbrella review of 21 published meta-analyses. British Journal of Sports Medicine. 2020;54(11):681-8.
6. Polito MD, Souza DB, Casonatto J, Farinatti P. Acute effect of caffeine consumption on isotonic muscular strength and endurance: A systematic review and meta-analysis. Science & Sports. 2016;31(3):119-28.
7. Grgic J, Garofolini A, Pickering C, Duncan MJ, Tinsley GM, Del Coso J. Isolated effects of caffeine and sodium bicarbonate ingestion on performance in the Yo-Yo test: A systematic review and meta-analysis. Journal of Science and Medicine in Sport. 2020;23(1):41-7.
8. Ribeiro BG, Morales AP, Sampaio-Jorge F, de Souza Tinoco F, de Matos AA, Leite TC. Acute effects of caffeine intake on athletic performance: A systematic review and meta-analysis. Revista Chilena de Nutrición. 2017;44(3):283-91.
9. Shen JG, Brooks MB, Cincotta J, Manjourides JD. Establishing a relationship between the effect of caffeine and duration of endurance athletic time trial events: A systematic review and meta-analysis. Journal of Science and Medicine in Sport. 2019;22(2):232-8.
10. Mielgo-Ayuso J, Calleja-Gonzalez J, Del Coso J, Urdampilleta A, León-Guereño P, Fernández-Lázaro D. Caffeine Supplementation and Physical Performance, Muscle Damage and Perception of Fatigue in Soccer Players: A Systematic Review. Nutrients. 2019;11(2):440.
11. Salinero JJ, Lara B, Del Coso J. Effects of acute ingestion of caffeine on team sports performance: a systematic review and meta-analysis. Research in Sports Medicine. 2019;27(2):238-56.
12. Ferreira TT, da Silva JVF, Bueno NB. Effects of caffeine supplementation on muscle endurance, maximum strength, and perceived exertion in adults submitted to strength training: a systematic review and meta-analyses. Critical Reviews in Food Science and Nutrition. 2020:1-14.
13. Raya-González J, Rendo-Urteaga T, Domínguez R, Castillo D, Rodríguez-Fernández A, Grgic J. Acute Effects of Caffeine Supplementation on Movement Velocity in Resistance Exercise: A Systematic Review and Meta-analysis. Sports Medicine. 2020;50(4):717-29.
14. Souza DB, Del Coso J, Casonatto J, Polito MD. Acute effects of caffeine-containing energy drinks on physical performance: a systematic review and meta-analysis. Eur J Nutr. 2017;56(1):13-27.
15. Mielgo-Ayuso J, Marques-Jiménez D, Refoyo I, Del Coso J, León-Guereño P, Calleja-González J. Effect of Caffeine Supplementation on Sports Performance Based on Differences Between Sexes: A Systematic Review. Nutrients. 2019;11(10):2313.
16. Da Silva LA, Wouk J, Reis Weber VM, de Almeida P, Lacerda Martins JC, Maneck Malfatti CR, et al. Caffeine and Glucose Metabolism at Rest Period, During, and Post Exercise in Diabetes Mellitus: A Systematic Review. Current Nutrition & Food Science. 2018;14(4):293-9.
17. Cheung HTH. Impact of caffeine on macronutrient metabolism: A review of literature. 2016.
18. Tabrizi R, Saneei P, Lankarani KB, Akbari M, Kolahdooz F, Esmaillzadeh A, et al. The effects of caffeine intake on weight loss: a systematic review and dos-response meta-analysis of randomized controlled trials. Critical Reviews in Food Science and Nutrition. 2019;59(16):2688-96.
19. Schubert MM, Irwin C, Seay RF, Clarke HE, Allegro D, Desbrow B. Caffeine, coffee, and appetite control: a review. International journal of food sciences and nutrition. 2017;68(8):901-12.
20. Phung OJ, Baker WL, Matthews LJ, Lanosa M, Thorne A, Coleman CI. Effect of green tea catechins with or without caffeine on anthropometric measures: a systematic review and meta-analysis. The American Journal of Clinical Nutrition. 2009;91(1):73-81.
