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Caffeine and Exercise – Can it Improve Performance?

ISSA, International Sports Sciences Association, Certified Personal Trainer, ISSAonline, Caffeine and Exercise – Can it Improve Performance?

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As a personal trainer, you will always field questions from clients about the latest supplements. While it is not within your scope of practice to recommend any, you should be up to date on trends and able to answer questions. 

Caffeine is a regular part of most diets, usually in the form of coffee, but studies show caffeine might actually improve exercise performance and aid fat loss. But is it right for your clients? Give them the information so they can discuss caffeine supplementation with their doctors.

What is Caffeine? 

Caffeine is a natural chemical found in coffee beans, tea leaves, cacao, and kola nuts. Many products include natural caffeine or a synthetic form. Energy drinks, some pain relievers, and over-the-counter medicines for improving alertness often contain added, synthetic caffeine. 

Most people consume caffeine in beverages, which contain varying amounts (1):

  • An eight-ounce cup of coffee has between 95 and 200 milligrams (mg) of caffeine. 
  • An eight-ounce cup of tea has 14 to 60 mg of caffeine, depending on the type. Black tea is highest in caffeine. 
  • A 12-ounce can of cola contains 35 to 45 mg. 
  • An eight-ounce energy drink may have between 70 and 100 mg. 
  • Caffeine supplements may contain anywhere from 100 to 900 mg. 

The healthy upper limit for caffeine intake is generally considered to be 400 mg per day, although everyone is different. Some people become jittery and anxious or can’t sleep with smaller amounts of caffeine, while others tolerate higher amounts. 

Caffeine and Exercise – Start with the Brain

Anyone drinking coffee, tea, or most energy drinks knows that caffeine is a stimulant. It wakes you up in the morning and picks you up in the afternoon. For those hooked on a morning coffee habit, it’s obvious that caffeine affects the mind, clearing out that early fog and improving focus. 

In terms of exercise performance, the effects of caffeine on the central nervous system may be beneficial. These effects may reduce fatigue and improve motivation to workout, for instance: 

  • Caffeine acts as a central nervous system stimulant, increasing brain activity, alertness, blood pressure, and body temperature. (2)
  • As a stimulant, caffeine can make you feel less fatigued and more energetic, although it does not actually treat fatigue’s underlying causes. (2) 
  • Some studies have shown that regular caffeine consumption is associated with a lower risk of depression. (3)
  • Caffeine can help manage headaches, along with over-the-counter painkillers. (4)  

In an indirect way, caffeine can be an exercise booster if it helps you feel more energized or manages headaches and depression symptoms that keep you out of the gym. 

ISSA, International Sports Sciences Association, Certified Personal Trainer, ISSAonline, Caffeine and Exercise – Can it Improve Performance?

How Caffeine Impacts Exercise Performance

While caffeine’s effect on waking up the brain and reducing fatigue are well-noted, athletes are more interested in what it does to the body. Several studies have shown that caffeine supplementation can improve exercise performance in a few ways. 

Before your clients try any supplement for athletic performance, share this workout supplement information with them

Caffeine and Exercise Endurance

Caffeine’s positive impact on endurance is well known. Certain athletic organizations have even banned high doses before events. Several studies prove the effect: 

  • A study tested the use of water, carbohydrates, and caffeine on endurance in cyclists. The caffeine supplement was superior to water and carbs. The athletes received 250 mg of caffeine at 15-minute intervals during a 90-minute session. (5)
  • Another study involving cyclists found that caffeine and carbs together improved endurance performance compared to just carbs or just water. The improvement was 9% better than the controls. (6)
  • A study involving runners found that those who drank regular coffee first ran faster than those who drank decaf coffee. The coffee seemed to reduce the athletes’ perception of effort, which may explain the improved speed and endurance. (7)

Caffeine and Strength Training

Research into how caffeine impacts strength exercises is limited compared to the research conducted on endurance. The studies that have been conducted show mixed results. Some indicate caffeine improves power in large muscle groups but not smaller ones. (8)

As with cardio endurance studies, caffeine can also improve muscle endurance. In general, the evidence suggests that caffeine is most useful in strength training for endurance and for power exercises with big muscle groups. 

Power and High-Intensity Exercises on Caffeine

Evidence from studies of high-intensity and power-focused workouts suggests that caffeine can be a benefit, but only for trained athletes. The benefits are minimal or non-existent for beginners. 

One study of competitive cyclists found that caffeine improved power during anaerobic exercises. They performed leg and chest presses as well as Wingate tests, bike sprints that measure peak anaerobic power. The athletes lifted more weight and reached a higher peak power in the sprints when using caffeine as compared to placebo. (9)

Another study looked at high-intensity team sports by giving rugby players either a placebo or a dose of caffeine supplement before testing game skills. The results indicated that those with caffeine performed better in all measures: sprinting speed, power generation in first and second drives, and passing accuracy. (10)

Caffeine and Fat Burn

Some of your clients may be interested in using caffeine as an aid to weight loss or for changing body composition. Many weight loss supplements have used caffeine as an ingredient for years. Research evidence suggests that caffeine does promote fat loss but alone does not contribute to long-term, overall weight loss. 

Caffeine may be a useful supplement for weight loss if it is used along with other healthy habits, like exercise and a balanced diet. A study of obese and overweight participants included a restricted diet with high-caffeine green tea or placebo found that those receiving caffeine lost more weight. They lost weight through fat loss and because the hunger hormone, leptin, was suppressed. (11)

Research indicates that caffeine may help with weight loss and maintenance by reducing hunger and by increasing fat loss. Caffeine supplementation before and during exercise seems to increase calorie burn. Some suggest that caffeine helps spare glycogen, which forces the body to turn to fat for energy. 

Learn more about caffeine and fat metabolism here

Risks of Supplementing Caffeine for Performance or Weight Loss

All the benefits of caffeine supplementation seem promising, but no supplement, natural or not, is without risks and side effects. First, it’s important to realize that people react differently to caffeine. You may have a client who drinks five cups of coffee a day with no adverse effects. Another client may get jittery or nauseated after one cup. 

As a personal trainer, you cannot recommend caffeine supplementation or any amounts. If you have a client interested in the benefit of caffeine for exercise and athletics, give them the information. They can then talk to their doctors about safe amounts to try. 

With that in mind, make sure your clients know that there are risks and side effects associated with using more caffeine than their bodies can handle (1):

  • Shakiness, restlessness
  • Muscle tremors
  • Insomnia
  • Headaches
  • Dizziness
  • Dehydration
  • Anxiety
  • Irritability
  • Abnormal or fast heart rhythms
  • Frequent urination
  • Harmful interactions with medications or other supplements

Caffeine is also habit-forming, and while it may not be as serious as an addiction to alcohol or an illicit drug, caffeine addiction can be problematic. It causes withdrawal symptom, for instance. Without caffeine you may experience headaches, difficulty focusing, irritability, and fatigue. This makes it a difficult habit to break. 

Supplementing with caffeine for better athletic performance is safe for many people. For others, it may not be worth the side effects. Help your clients stay informed so they can make good decisions with the guidance of their doctors. 

The ISSA’s Certified Personal Trainer – Self-Guided Study Program can help you take the next step to turn your passion into a career. Learn everything you need to work as a trainer and to stay up to date on fitness, nutrition, and supplement trends.



  1. MedlinePlus. (2020, October 6). Caffeine. Retrieved from
  2. Institute of Medicine. (2014). Caffeine in Food and Dietary Supplements: Examining Safety: Workshop Summary. Retrieved from
  3. Lucas, M., Mirzaei, F., Pan, A., Okereke, O.I., Willett, W.C., O’Reilly, E.J., Koenen, K., and Ascherio, A. (2011, September 26). Coffee, Caffeine, and Risk of Depression Among Women. Arch. Intern. Med. 171(17), 1571-8. Retrieved from
  4. Lipton, R.B., Diener, H., Robbins, M.S., Garas, S.Y., and Patel, K. (2017, October 24). Caffeine in the Management of Patients with Headache. J. Headache Pain. 18(1), 107. Retrieved from
  5. Ivy, J.L., Costill, D.L., Fink, W.J., and Lower, R.W. (1979). Influence of Caffeine and Carbohydrate Feedings on Endurance Performance. Med. Sci. Sports. 11(1), 6-11. Retrieved from
  6. Huston, C.J. and Jeukendrup, A.E. (2008, December). Substrate Metabolism and Exercise Performance with Caffeine and Carbohydrate Intake. Med. Sci. Sports Exerc. 40(12), 20196-104. Retrieved from
  7. Demura, S., Yamada, T., and Terasawa, N. (2007, December). Effect of Coffee Ingestion on Physiological Responses and Ratings of Perceived Exertion During Submaximal Endurance Exercise. Percept. Mot. Skills. 105(3 Pt 2), 1109-16. Retrieved from
  8. Warren, G.L., Park, N.D., Maresca, R.D., McKibans, K.I., and Millard-Stafford, M.L. (2010, July). Effect of Caffeine Ingestion on Muscular Strength and Endurance: A Meta-Analysis. Med. Sci. Sports Exerc. 42(7), 1375-87. Retrieved from
  9. Woolf, K., Bidwell, W.K., and Carlson, A.G. (2008, August). The Effect of Caffeine as an Ergogenic Aid in Anaerobic Exercise. Int. J. Sport Nutr. Exerc. Metab. 18(4), 412-29. Retrieved from
  10. Stuart, G.R., Hopkins, W.G., Cook, C., and Cairns, S.P. (2005, November). Multiple Effects of Caffeine on Stimulated High-Intensity Team-Sport Performance. Med. Sci. Sports Exerc. 37(11), 1998-2005. Retrieved from
  11. Westerterp-Plantenga, M.S., Lejuene, M.P.G.M., and Kovacs, E.M.R. (2005). Body Weight Loss and Weight Maintenance in Relation to Habitual Caffeine Intake and Green Tea Supplementation. Obes. Res. 13(7), 1195-204. Retrieved from

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