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The Effects of Caffeine on Endurance Athletes
Mia Bickley
School of Health Sciences and Allied Health Professions
EXSC 320: Measurement and Evaluation in Health and Kinesiology
Dr. James Schoffstall
January 31, 2025
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Annotated Bibliography
1. Andreas, Kreutzer; Austin J. Graybeal; Kamiah, Moss; Robyn, Braun-Trocchio; Meena,
Shah. (2022). Caffeine Supplementation Strategies Among Endurance Athletes. Front. Sports
Act. Living 4, 10.3389.
•Introduction: Caffeine is much more prevalent in professional (45.5%), and recreational
athletes (25.1%) than in collegiate athletes (9.4%). The participants said overall they noticed a
small to moderate effect when it came to consuming caffeine. And the recreational athletes
typically had lower amounts of caffeine.
•Methods: This study was done through an electronic survey via Qualtrics to investigate
caffeine consumption and supplementation strategies. Around 254 endurance athletes
completed the survey. There were 134 females, and around 120 males. Various questions were
asked regarding caffeine amounts, and how the participants consumed their caffeine.
•Results: Caffeine supplements seemed to be much more prevalent among men compared to
women. Collegiate athletes had a lower prevalence of caffeine supplementation (9.4%)
compared to recreational athletes (25.1%) and professional athletes had the highest prevalence
when it came to caffeine (45.5%) Participants reported to have greater caffeine effectiveness in
races compared to training.
•Discussion: In this study, about 85% of the participants reported to consume caffeine
habitually. And most of the participants said that they used energy gels as their main source of
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caffeine during training and races or events. However, it is unclear as to how effective they
are, as they have often been compared to placebos.
2. Apostolidis Andreas; Vassilis, Mougios; Ilias, Smilios; Maria, Frangous; & Marios,
Hadjicharalambous. (2022). Caffeine Supplementation is Ergogenic in Soccer Players
Independent of Cardiorespiratory or Neuromuscular Fitness Levels. Journal of the
International Society of Sports Nutrition, 10.1186.
•Introduction: Begins with saying that early studies suggested that caffeine may enhance fat
oxidation and improve endurance performance by promoting intramuscular carbohydrate
sparing, however other studies have failed to prove this. And then later on, the article states
that caffeine has been found to increase anaerobic performance and Wingate peak, as well as
other exercises and tests. It does also acknowledge that there can be some differences when it
comes to factors such as age, sex, training experience, as well as caffeine dosage.
•Methods: There were twenty healthy male soccer players that participated in the study. The
participants had previous history of at least five years of professional soccer, or semi-
professional soccer. They did two exercise trials, separated by 4 days, consuming rouhgly 6
mg of caffeine or a placebo in a double-blind and counterbalanced manner. One trial included
three 22.5 minute periods of running at various speeds on a treadmill.
•Results: There was a significant difference in the time to exhaustion when it came to the group
that was given caffeine versus the group that was given the placebo. The group that was given
caffeine had a longer time to exhaustion compared to the group that was given the placebo.
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And three of the participants who performed the caffeine trial after the placebo trial noticed
their longer times to exhaustion and guessed they had taken caffeine.
•Discussion: In the discussion section, it said that body mass and body fat did not influence the
caffeine responses despite those two varying within the groups. It also showed that the
ergogenicity of caffeine on endurance performance cannot be attributed to metabolic effects.
And finally, the study did show that caffeine was effective in improving endurance and
neuromuscular performance and the ergogenicity of caffeine does not depend on
cardiorespiratory or neuromuscular factors.
3. Belbis, D. Michael; Camic, L. Clayton; Howell, M. Steven; Zhang, Shuqi; Chomentowski, J.
Peter. (2022). The Effects of Acute Caffeine Supplementation on Repeated-Sprint Ability in
Healthy Young Athletes. Int J Exerc Sci. 15(2), 10.70252.
•Introduction: There are possible improvements when it comes to elevated blood flow and
muscle oxygenation. Many studies have been done for the overall effects of caffeine while this
one seems to look into the short-term, high-intensity, and repeated bouts of exercise. The
stated purpose of the study is to establish the impact of 200 mg of caffeine on repeated-sprint
running performance in young, and healthy non-athletes.
•Methods: Thirty-two participants were asked to partake in the study. The participants were
men and women ranging from eighteen to thirty years of age. The subjects were assigned to a
randomized, double-blind, placebo-controlled trial. The caffeine dosage ranged from 150-250
mg.
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•Results: There was a significant reduction in total sprint time during all of the three three
sprint sets that were done. There was not a notable difference when it came to the heart rate
for each set. And there was no significant difference in the rate of paercieved exertion between
the caffeine and the placebo trials.
•Discussion: In this study, results showed that both systolic and diastolic blood pressure were
significantly increased after sixty minutes of caffeine ingestion. The elvations in blood
pressure ranged from five to fifteen mmHg systolic and five to ten mmHg diastolic. Overall, a
lower dosage of caffeine was found to improve the performance in a repeated-sprint in semi-
professional soccer players.
4. Burke, I. Benjamin; Travis, Kyle S.; Gentles, A. Jeremy; Sato, Kimitake; Lang, M. Henry;
Bazyler, D. Caleb. (2021). The Effects of Caffeine on Jumping Performance and Maximal
Strength in Female Collegiate Athletes. Nutrients 13(8), 10.3390.
•Introduction: Caffeine has been shown to increase the release of calcium from the
sacroplasmic reticulum which can lead to enhanced force production. Males and females have
exhibited different responses to caffeine because of differences in circulating steroid hormones.
Some studies have shown increased vertical jump height in a mixed subject population
(trained, and untrained)
•Methods: This study was done in a double-blind, placebo-controlled manner. Athletes
received 6 mg/kg of caffeine in pill form with 250 mL of water. The placebo was Sucralose
which was administered in the same fashion. The participants were eleven female collegiate
volleyball players and eight female weightlifters.
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•Results: There were no significant differences between the caffeine and the placebo. However
there were different time effects for heart rate. There were no significant differences for the
rate of perceieved exertion, but there were some notable differences in systolic blood pressure.
•Discussion: There was overall a small, yet significant effect on jumping performance. There
was not any noticeable effects when it came to the maximal isometric strength for caffeine
consumption. The only major physiological measurement that was altered by caffeine
compared to the placebo was resting systolic blood pressure
5. Dittrich, Naiandra; Serpa, Marília C.; Lemos, Elisa Cristina; De Lucas, Ricardo D.;
Guglielmo, Luiz Guilherme A. (2021). Effects of Caffine Chewing Gum on Exercise
Tolerance and Neuromuscular Responses in Well-Trained Runners. Journal of Strength and
Conditioning Research 35(6), 10. 1519.
•Introduction: Acknowledges caffeine’s ability to act as an adenosine receptor antagonist
which can induce effects on both the central and peripheral systems which reduce the rate of
perceieved exertion. Says that knee extensors seem to be more receptive to caffeine ingestion
than other muscle groups. Possibly related to the muscle size since with smaller muscles, the
activation is already near 100% so there is only a little bit of room for improvement.
•Methods: This study was a randomized, placebo-controlled, double-blind trial and involved
repeated measures of the same participants. The subjects involved in the study were twelve
trained male endurance runners with at least three years of experience. Some equipment that
was used in the study include an isokinetic dynamometer (Biodex System 3), and a surface
electromyography was used to measure muscle activity.
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•Results: There weren’t any significant interactions between running conditions, and time. The
main effect was pertaining to heart rate, and the respiratory exchange ratio. No significant
difference was found when it came to the VO2.
•Discussion: The study says that enhancement induced by caffeine ingestion is very well
known for endurance events, however the mechanisms responsible are still limited. The results
of the study showed that peripheral and central nervous system mechanisms decreased at the
same magnitude. Only a few studies have looked into caffeine’s effects associated to
neuromuscular fatigue.
6. Filip-Stachnik, Aleksandra; Wilk, Michal; Krzysztofik, Michal; Lulińska, Ewelina; Tufano,
J. James, Zajac, Adam; Stastny, Petr; & Coso, Del Juan. (2022). The Effects of Different
Doses of Caffeine on Maximal Strength and Strength-Endurance in Woman Habituated to
Caffeine. Journal of the International Society of Sports Nutrition 18(1), 10.1186.
•Introduction: The ergogenic effect of caffeine has been found to be effective when three to
thirteen mg/kg body mass and ingested within 30-90 minutes before exercise in the form of
capsules. The impact of caffeine is linked to the hydrophobic nature of caffeine, a high
capacity for distribution, and it’s lipophilic nature allows caffeine to enter all tissues. More
effects of caffeine include enhanced fat oxidation, increased muscle oxygen saturation, and
local changes within the exercising muscle.
•Methods: Twenty-one healthy females volunteered to participate in this study. They have at
least two years of resistance training. Each participant acted as her own control in this double-
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blind, randomized study. There was one familiarization session which included 1 RM tests,
and a strength-endurance test.
•Results: There were no major effects of substance for the number of performed repetitions.
The 1 RM tests seem to be most consistent when it comes to an actual caffeine supplement
versus the placebo. And peak velocity, and output during the strength-endurance tests seem to
be higher for both the placebo and the actual caffeine supplement compared to the mean
velocity, and power output.
•Discussion: Typically for those who habitually consume caffeine, there is a tolerance that is
built and it can be seen in this study. There was not much of a difference when it came to the
groups who consumed 3 mg/kg of caffeine versus 6 mg/kg. And gender may play a factor into
this as well. Females typically have a higher portion of type I fibers, and greater muscle
capilarry density with distinct glycolytic and oxidative capacities.
7. Grgic, Jozo; Venier, Sandro; Mikulic, Pavle. (2022). Examining the Effects of Caffeine on
Isokinetic Strength, Power, and Endurance. J. Funct. Morphology. Kinesiol. 7(4), 10.3390.
•Introduction: This study says there’s a possibility that caffeine’s effects may be muscle-group
specific. Researchers have been advocating for a no-placebo control trial when testing caffeine
and its impacts on performance. There is also a chance that caffeine’s benefits on exercise
performance may be due to plaebo effects.
•Methods: The participants were all male, and ranged between 18-45 years old. Some
equipment that was used includes an isokinetic dynamometer (a Systen 4 Pro). ANOVA was
also used in this study.
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•Results: It seemed that there seemed to be quite an effect when it comes to knee extension.
There wasn’t much of an effect for knee flexion. And overall, there weren’t any significant
differences between the actual caffeine supplement versus the placebo.
•Discussion: Several factors were tested and evaluated such as peak torque, average power, and
total work. There were two muscle groups that were targeted at lower and higher angular
velocities. Overall, caffeine enhanced isokinetic strength, power, and endurance of the knee
extensors and there were no notable differences between the placebo and control trials.
8. Karayigit, Raci; Naderi, Alireza; Akca, Firat; Janssen Gomes da Cruz, Carlos; Sarshin, Amir;
Yasli Caglar, Yasli; Ersoz, Gulfem; Kaviani, Mojtaba. (2021). Effects of Different Doses of
Caffeinated Coffee on Muscular Endurance, Cognitive Performance, and Cardiac Autonomic
Modulation in Caffeine Naive Female Athletes. MDPI. 13(1), 10.3390.
•Introduction: While caffeine about 60 minutes before exercise can help with reaction time,
cognition, and mood, the article says that doses above 500 mg may cause the opposite reaction
that includes performance decrements, anxiety, and tension. It is also said that anhydrous
caffeine is not better than caffeinated coffee for sprint, and muscular endurance performance.
•Methods: Seventeen healthy female team sport athletes participated in the study. Ten of which
played rugby, four played handball, and three played soccer. All of the participants were
around twenty-three years of age. The study was double-blind, and counter-balanced. Various
exercises and evaluations were done ranging from bench press, to back squat, to five minutes
of jogging on a treadmill.
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•Results: There was no significant difference between the first and second familiarization
sessions. There were no significant effects when it came to pain perception, and there were no
significant differences when it came to cognitive performance. The performance quality
increased when it came to the lower body compared to the upper body.
•Discussion: In this study, there seemed to be a minimal overall effect when it comes to
caffeine’s ergogenic effects. The article also says that slow-twitch muscle fibers are possibly
more sensitive to caffeine ingestion than fast-twitch muscle fibers. Which means that
depending on the contraction type, the performance may be impacted.
9. Yusuf, Buzdagli; Aslihan, Tekin; Erdinc, Siktar; Gunay, Eskici. (2021). Effect of Caffeine on
Exercise Performance. Turkish Journal of Sport and Exercise 23(1), 10.15314.
•Introduction: In the west, 90% of adults consume caffeine regularly. And daily caffeine
consumption in the US for adults is estimated to be 200 mg. Caffeine effects fat metabolism,
metabolic disorders, cognitive performance, and dehydration.
• Methods: Twenty-one trained male athletes were given a gelatin capsule about one hour
before competing in a multi-sprint trial. The capsules contained about 5 mg/kg of caffeine and
a placebo which was maltodextrin. The study proved that caffeine does in fact improve
repetitive sprint performance, but does not affect maximum strength performance.
•Results: The most common consumption form of caffeine with or without training in strength
studies is 3-6 mg/kg about ninety minutes before exercise specifically in pill or capsule form.
And while caffeine does help with reaction time, it is still unknown as to whether it hinders
problem solving and decision making.
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•Discussion: Caffeine has ben shown to increase the sympathetic nervous system activity and
release fatty acids from adipose tissue. It occurs indirectly through increased adrenaline levels,
and can potentially increase availability of fatty acids for oxidation. Caffeine also has a direct
effect on lipolysis.
10. Ziyu, Wang; Bopeng, Qiu; Jie, Gao; & Juan del, Coso. (2023). Effects of Caffeine Intake on
Endurance Running Performance and Time to Exhaustion. MDPI, 10.3390.
•Introduction: In the article, it says that the effect of caffeine is obtained through many
physiological mechanisms which include an increased central nervous system drive, and
enhanced skeletal muscle contractile capacity. It also says that there is a consensus
establishing the ability of caffeine to act as an adenosine receptor antagonist as the main
mechanism. That means the blockage of adenosine receptors with caffeine would impact the
release of hormones such as norepinephrine, dopaine, acetylcholine, and serotonin.
•Methods: The study was done in a single- or double-blind manner. Any form of caffeine
intake was included in the study. The study was done with a group of trained runners, and
recreational runners. There were 254 participants in total. 220 of which were men, 19 women,
and 15 with no information about gender. 167 were categorized as amateur runners, and 87
were categorized as trained. The doses of caffeine ranged from 3 to 9 mg/kg. There was a
range of running between 800 to 5,000 meters and there was the other group which covered
more than 5,000 meters.
•Results: Overall, the caffeine increased time to exhaustion in the recreational runners
specifically. It was also revealed that caffeine was not ergogenic when it came to the middle-
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distance or the long-distance trials of the studies. And that caffeine did not improve endurance
running performance when it came to the timed trials done by trained runners.
•Discussion: Caffeine may have inhibitory effects on perceptual responses when it comes to
exercising. Which meant that it helped the participants tolerate the feelings of fatigue during
exercise. Overall, the effects of caffeine when it came to improving running time trial
performance was not very high. There was a moderate ergogenic effect to increase the time to
exhaustion, and a little effect to improve performance in running time trials.
