Caffeine is a popular supplement used to improve performance and increase alertness. Americans consume 200-300 milligrams of caffeine per day. As one of the most widely used ingredients in pre-workout supplements, it’s important to verify its efficacy in improving exercise outcomes.

What is Caffeine?

Caffeine is a substance found naturally in many plants. It’s also abundant in coffee, tea, soda, and chocolate, and is taken in powders, pills, or an ingredient in energy supplements1.

Adenosine slows down nerve cell activity and causes drowsiness. Caffeine binds to the same receptors as adenosine, blocking its effects. This causes increased neuron firing. The pituitary gland registers this activity as an emergency. This releases hormones causing increased breathing, heart rate, blood flow to muscles, and blood pressure. It also decreases blood flow to the stomach and releases sugar into the blood for extra energy1.

Based on this information, caffeine seems effective in improving performance in a number of scenarios, including strength training. There are plenty of studies looking into how effective caffeine is in strength training.

What does the research say about caffeine and strength?

Study 1: The Acute Effects of a Caffeine Containing Supplement on Strength, Muscular Endurance, and Anaerobic Capabilities2

This study examined the effects of caffeine on strength in 37 men. On the first visit, the participants completed two Wingate Anaerobic Tests to determine peak power, mean power, and muscular endurance & strength. Two days later, the subjects were split into two groups: supplement group and placebo group.

One hour after taking the caffeine supplement (or placebo), subjects performed  two Wingate Anaerobic Tests followed by endurance and strength exercises on the leg extension and bench press. Researchers saw a significant increase in strength when measured on the bench press but did not see an increase on the leg extension. Researchers concluded caffeine may be an effective supplement for improving upper body strength.

Study 2: Effects of coffee and caffeine anhydrous on strength and sprint performance3

The next article examined the effects of coffee and caffeine on performance. The study used 54 male participants. Subjects tested on one repetition max and repetitions to fatigue on the leg press and bench press. Subjects then completed 5 second and 10 second cycle sprints with one minute of rest between each sprint. Participants returned 48 hours later and either took 300mg of caffeine, 303mg of caffeine in coffee, or a placebo. The subjects then repeated the tests.

The results were mixed. The one rep max on the leg press improved more in the coffee group than the caffeine group. Changes were not observed in the one rep max or reps to fatigue on the bench press. There were also no changes to the reps to fatigue on the leg press. The caffeine group saw better performance than the coffee and placebo group on sprints. The placebo group saw a significant decrease in sprint performance that was not present in the supplemented groups. Neither the coffee nor the caffeine group saw superior strength improvements than the placebo group.

Study 3: Effects of Caffeine on Repetitions to Failure and Ratings of Perceived Exertion During Resistance Training4

The next study examined the effects of caffeine on number of repetitions completed and athletes’ rating of perceived exertion during a strength workout. Seventeen subjects were included in this study. Subjects were initially given a 10 repetition bench press and leg press test. In the second and third session, participants were assigned to either a supplement or placebo group. The supplement group took approximately 6mg/kg of caffeine (2.7mg/lb example: 459mg for a 170 pound individual) one hour prior to the tests.

The supplement group completed significantly more repetitions after multiple sets on the leg press. There were no significant differences on the bench press. There was also no significant difference in the ratings of perceived exertion between the two groups. Researchers concluded caffeine can delay fatigue in high intensity training programs.

Study 4: Effect of caffeine ingestion on one-repetition maximum muscular strength5

The final study looked at the effects of caffeine on short term, high intensity exercise. Twenty two men were split into two groups: a caffeine group, and a placebo group. The caffeine group took a supplement containing 6mg/kg (2.7mg/lb) of caffeine. All 22 subjects completed a one repetition max test on the bench press and leg press. The subjects then completed repetitions to failure on both exercises.

The results showed caffeine did not affect the one repetition max on either the bench press or leg press. Caffeine slightly increased the total amount of weight lifted on the subsequent repetitions to fatigue tests on both the bench press and leg press. Subjects’ rate of perceived exhaustion was similar in both groups. Researchers concluded caffeine intake did not significantly alter muscular strength or endurance on the bench press or leg press.

Is caffeine effective at increasing strength?

The studies on whether caffeine improves strength are at best, mixed. Among studies that saw an increase in strength, one study found it was effective for upper body strength but not lower. Another study found caffeine improved lower body strength but not upper. Other studies did not find any strength improvements with supplementation.

The Bottom Line

Caffeine may have limited benefits for some individuals in resistance and strength training. It’s probably not a magic pill that makes or breaks a strength routine. It can however, slightly increase strength, delay fatigue, and improve endurance performance.


  1. About Caffeine. (n.d.).
  2. Beck, T. W., & Housh, T. J. (2006). The Acute Effects Of A Caffeine-Containing Supplement On Strength,muscular Endurance, And Anaerobic CapabilitiesJournal of Strength and Conditioning Research, 20(3), 506-510. doi:10.1519/00124278-200608000-00008
  3. Trexler, E. T., & Roelofs, E. J. (2015). Effects of coffee and caffeine anhydrous on strength and sprint performanceJournal of the International Society of Sports Nutrition, 12(S1). doi:10.1186/1550-2783-12-s1-p57
  4. Green, J. M., & Wickwire, P. J. (2007). Effects of Caffeine on Repetitions to Failure and Ratings of Perceived Exertion during Resistance TrainingInternational Journal of Sports Physiology and Performance, 2(3), 250-259. doi:10.1123/ijspp.2.3.250
  5. Astorino, T. A., & Rohmann, R. L. (2007). Effect Of Acute Caffeine Ingestion On One-Repetition Maximum Muscular StrengthMedicine & Science in Sports & Exercise,39(Supplement). doi:10.1249/01.mss.0000273058.88299.68
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