Every athlete's body is different and if you have a sluggish metabolism, you could benefit from using caffeine. Caffeine increases the rate at which you burn energy and this effect can continue for at least three hours.

To achieve the best results, consider speaking with your coach, nutritionist, or physician about using caffeine tablets to boost your metabolism.

Athletes and bodybuilders can burn fat and strengthen their muscles by using a typical dose of at least mg of caffeine before their workout. If you've never used caffeine it is best to start with a smaller dose and assess how your body responds.

When using caffeine before a workout, start out with the smallest dosage possible, so your body can enjoy the best effects without overusing this natural stimulant. Caffeine will enter your bloodstream within 15 minutes. Most people will experience the peak effects within 40 minutes to 80 minutes after consumption.

Most people will feel more energetic, alert, and focused making it an ideal supplement for athletes or anyone needing extra endurance.

Using caffeine for bodybuilding is great for most athletes but there are some exceptions to the rule. If you are pregnant or have a caffeine sensitivity, you should talk to your doctor before using caffeine for this purpose.

Also, If you have high blood pressure, you should talk to your physician if you want to use caffeine as a pre-workout. Bodybuilders and athletes with acid reflux should also be careful when using caffeine, even in a casual manner before a workout.

There are several medical conditions that may make it difficult for you to use a stimulant without risk. While you may already be aware of anything that may require you to be cautious, it is important to talk to your doctor before you start using any type of supplement regularly.

In some cases, caffeine pills have several advantages over pre-workout. Caffeine pills are convenient, act as a rich source of antioxidants, and do not contain any additives. Caffeine pills supply the same amount of coffee as a cup of coffee. That is, you'll get mg of caffeine in a fast and easy to consume form, without having to stop and drink a cup of coffee.

Since caffeine tablets are free from fluid, you won't have to worry about stopping during training or competition. Additionally, the acidic compounds in some coffee are not present, so caffeine pills are less initiating to your gastrointestinal tract.

Because a caffeine tablet contains a precise quantity of caffeine, it's easy to meet dosage requirements. Caffeine pills are also affordable and usually work out better in terms of price than coffee pods or bags.

A pre-workout may contain a mix of ingredients, that is unfavorable to you. Several athletes are negatively impacted by additives that may be in some pre-workout.

Caffeine pills are more convenient than some pre-workouts and can be consumed on the go. With a caffeine pill, you can easily calculate how much caffeine you want to take. The amount of caffeine in the pill is stated directly, so you'll know, based on your body weight, how much you need to take to get the effect that you're looking for.

You can also adjust the dosage as necessary so that you don't get too much caffeine but don't feel fatigued during training. Click Here To Buy Caffeine mg Tablets. free shipping on all domestic orders weighing up to 1lb. Home Blog 3 Great Reasons Caffeine As Pre Workout Can Benefit Athletes.

How To Use Caffeine As Pre Workout How Do Athletes Use Caffeine For Bodybuilding Results? Bodybuilding Caffeine for Muscle Growth and Performance A study showed that caffeine can reduce muscle soreness that athletes and bodybuilders can experience after a workout. Caffeine Affects On Athletic Performance Caffeine can drastically affect athletic performance by increasing alertness and energy.

Caffeine Can Help Offset Fatigue Caffeine increases your body's resistance to fatigue, making it ideal for people who need to swim, cycle or run long distances during training or competition. Studies correlate its use to increased exercise performance in endurance activities, as well as its possible ergogenic effects for both intermittent and strength activities.

Recent findings show that caffeine may increase or decrease exercise performance. These antagonist responses may occur even when using the same dosage and for individuals with the same characteristics, making it challenging to explain caffeine's impact and applicability.

This review article provides an analytic look at studies involving the use of caffeine for human physical performance, and addresses factors that could influence the ergogenic effects of caffeine on different proposed activities.

These factors subdivide into caffeine effects, daily habits, physiological factors, and genetic factors. Each variable has been focused on by discussions to research related to caffeine. A better understanding and control of these variables should be considered in future research into personalized nutritional strategies.

Active individuals and elite athletes use caffeine purposely to improve performance. Athletes from different modalities consume caffeine, including endurance athletes e. In an evaluation of 20, urine samples of elite athletes, Although caffeine's ergogenic effect is well-established, several studies have shown differences in the magnitude of caffeine-mediated effects on exercise performance, where some individuals may not respond, or even negatively respond to the caffeine consumption Graham and Spriet, ; Meyers and Cafarelli, ; Wiles et al.

The possibility of inter-individual variability does not diminish the importance of applying caffeine to performance, but it underlines that caffeine's effects may be unclear under some conditions Skinner et al. There are several hypothetical mechanisms for caffeine-mediated improving performance Figure 1 , including calcium release from the sarcoplasmic reticulum Klein et al.

Thus, it is possible that one factor or a combination of these factors may be responsible for the increase in exercise performance after caffeine intake. Figure 1. Main mechanisms of action of caffeine-related to increases in training capacities.

A Antagonistic action of caffeine and its secondary metabolites to adenosine at its receptors in the Central Nervous System CNS , increasing alertness and decreasing perceived exertion in exercise.

B Effect of preserving muscle glycogen from a greater distribution of fatty acids in the bloodstream and energy use under some conditions. C Increased release of calcium ions by a neuromuscular stimulus, enhancing contraction power in muscle fibers. In this context, some factors are pointed regarding caffeine's effectiveness as an ergogenic aid, such as dose, training degree, ingestion time, time of day caffeine supply, habitual caffeine consumption, and proposed exercise type Collomp et al.

Additionally, recent findings related to genetic polymorphisms in the CYP1A2 and ADORA2A genes Womack et al. Therefore, this review aims to discuss the factors that could influence the ergogenic responses to caffeine, developing efficient nutritional strategies with that supplementation.

The well-accepted dosage of caffeine to improve performance is between 3 and 6 mg. It is currently established that the benefits of caffeine on performance occur through its direct action on the CNS, improving alertness and reaction time, in addition to reducing the perceived exertion rate pain Maughan et al.

It reinforces that the effects on improving performance with the consumption of low doses of caffeine are a consequence of its direct action on the CNS. In this context, Zhang et al. Their findings indicate that the ingestion of lower doses of caffeine triggered greater effects on cognition and brain activation when compared to moderate and higher doses 6 or 9 mg.

It highlights Spriet's positioning Spriet, , indicating that the use of moderate or higher doses would only be justified through peripheral effects of caffeine on performance tests see Figures 1B,C. Thus, further investigations involving the administration of higher doses of caffeine i.

Moreover, increasing the caffeine dose should be used based on the individual's tolerance to the substance and the type of physical exercise.

Some studies showed that aerobic exercises with higher doses of caffeine i. In those cases, caffeine altered the energetic use of the lipids with the maintenance of the muscle glycogen stocks Graham and Spriet, ; Spriet et al.

This mechanism triggered improvements in aerobic performance tests when a high dosage of caffeine has been ingested before Graham and Spriet, ; Spriet et al. In these two cases, both significant variations of the improvement in performance tests with higher doses of caffeine Graham and Spriet, ; Spriet et al.

These studies would allow a definitive position about the effect of caffeine on the oxidation of lipids. This is a very relevant mechanism since it is well-outlined that the drug induces lipolysis, which increases the availability of blood fatty acids, when caffeine is previously, during, or after physical exercise administered Spriet et al.

However, favoring energy production from this greater availability of mobilized fatty acids presents conflicting results Graham et al.

Besides, the latest international reports lack a definitive position on caffeine's possible ergogenic effects on strength-to-power exercises Goldstein et al. This occurs because the current literature is ambiguous regarding the relationship between caffeine intake and improvement in strength-to-power.

Whereas some studies Astorino et al. In this context, recent studies have shown that higher doses of caffeine above 6 mg. In these cases, the use of higher doses of caffeine could be triggering additional performance effects by increasing the calcium release from the sarcoplasmic reticulum Klein et al.

This hypothesis needs to be verified since there is also a recent study Polito et al. This inconclusive data spawns an interesting situation in which caffeine dosages between 3 and 6 mg.

Thus, higher caffeine dosage effects should be investigated based on the individual's substance's tolerance and acceptability. Genetic factors read sections ADORA2A Gene rs Polymorphism and CYP1A2 gene rs g. The isolated consumption of anhydrous caffeine induces maximum plasma peaks of the substance between 30 and 90 min after consumption of low 2—3 mg.

In addition, the use of caffeine occurs mostly 60 min before the performance tests endurance, team sports, combat sports, and strength-to-power activities Grgic et al.

Noteworthy, the current recommendations for optimal caffeine ingestion time in sports performance occur from scientific evidence that investigated the different times of ingestion of the substance from the performance of aerobic performance tests Bell and McLellan, ; Maughan et al.

In this context, Bell and McLellan reinforce that the caffeine supplementation 5 mg. In addition, Bell and McLellan demonstrated that consumption of the same dosage of caffeine 5 mg.

In this respect, it is worth noting that the process of metabolizing caffeine occurs through the reduction of plasma levels of the caffeine, with the gradual increase of its secondary metabolites Nehlig, In addition to its isolated use, the absorption kinetics of different caffeine doses 1.

The additional use of caffeine compared to the isolated consumption of carbohydrates triggered significant improvements both in the capacity for interval running Taylor et al.

In this context, the added caffeine seems to provide benefits, both in muscle recovery between two consecutives training sessions, and in ingestion during cycling tests Pedersen et al. The actual mechanisms behind caffeine use have yet to be investigated since the high dosage of caffeine 8 mg.

In addition, caffeine can also be administered through alternative forms of ingestion, such as food consumption coffee, teas, and energy drinks, for example , chewing gum, mouth rinses, and aerosol.

All recommendations are based on the delivery times of caffeine in the bloodstream. For a thorough review, the reader is referred to papers by Wickham and Spriet Caffeine withdrawal effects are present in all caffeine-related studies.

It occurs through caffeine restriction protocols source foods in the moments before the performance tests. The problem is that the caffeine restriction period varies in many studies, with depriving source-food of 6 h up to days Collomp et al.

This caffeine deprivation is necessary since its withdrawal in habitual users is related to the increased likelihood of caffeine Withdrawal symptoms, such as episodes of headache, increased sleepiness or tiredness, depression, irritability, and decreased alertness and productivity, nausea, and stiffness Juliano and Griffiths, ; Juliano et al.

These side-effects may impact the performance of control individuals placebo group , hindering the real understanding of the size of improvement following caffeine administration.

In this context, the lack of studies investigating the effects of caffeine withdrawal on exercise performance is surprisingly critical, especially in order to establish an efficient restriction protocol.

The unwanted effects of caffeine withdrawal are generally known to occur more prominently within 12—48 h after the last ingestion Griffiths and Woodson, ; Juliano et al. In addition, the caffeine half-life can vary from 3 to 7 h depending on some characteristics de Mejia and Ramirez-Mares, , raising severe doubts about the initial condition of the placebo groups with previous deprivation of caffeine in short periods 6—24 h Bell and McLellan, ; de Alcantara Santos et al.

However, as most of the reported symptoms are subjective Juliano and Griffiths, ; Juliano et al. In this sense, a recent study Juliano et al. The research tested the expectation of caffeine withdrawal through the consumption of a cup of coffee containing mg of caffeine or a decaffeinated version of it.

Caffeinated and decaffeinated coffees were delivered to the participants and were correctly or wrongly presented to them, creating four possible intake expectations among the individuals: real caffeinated coffee; fake caffeinated coffee; real decaffeinated coffee; fake decaffeinated coffee.

For each condition, the participants filled out a standardized questionnaire in accordance with self-reported measurements on the Withdrawal Symptom Questionnaire and Caffeine Craving for 24 h, showing that higher scores were correlated to the expected absence of caffeine consumption Juliano et al.

This nocebo effect due to the expectation of not consuming caffeine was also addressed in a study that performed the reduction of caffeine in habitual caffeine consumers, and it pointed out greater more withdrawal symptoms among the groups that had the perception of dose reductions during the taper dose Mills et al.

This reinforces the need for experimental designs that blind the sample to caffeine administration before performance tests. It is currently unclear whether caffeine withdrawal could cause negatively affect physical performance or whether the reduction of withdrawal symptoms provided by well-blinding the sample could impact exercise performance.

This should be focused on future research to avoid serious questions about caffeine's effectiveness on increasing exercise performance James and Rogers, Caffeine is a substance presented in a range of in natura foods, and industrialized products, commonly consumed by almost every nation in the world Magkos and Kavouras, ; Mitchell et al.

Animal studies indicate chronic caffeine consumption induces neural adaptations correlated to adenosine receptors Boulenger et al.

These neural adaptations increase the number of adenosines binding sites, decreasing the development of caffeine stimulating action triggering lower tolerance of caffeine.

These neural adaptations increase the number of adenosine binding sites. This may decrease caffeine stimulating action triggering tolerance to its effects. However, there are conflicting results between the studies applied to human performance Dodd et al. In this context, Dodd et al.

The individuals were subjected to an incremental cycle ergometer test, with increases of 30 w every 2 min until subjects could not maintain the stipulated cadence. After placebo or caffeine supplementation 3 or 5 mg. This same indifference was also observed by Gonçalves et al.

The study indicated that the caffeine supplementation 6 mg. Aspects such as the lack of chronic supplementation, a variation of caffeine content in food sources, and the absence of blood circulating caffeine in the participants are strong limitations that must be considered in future studies McCusker et al.

A higher ergogenic effect was noticed after receiving caffeine over placebo, with major benefits among non-users and, also, when the exercise-initiated 1 h after caffeine consumption. Beaumont et al. After the chronic caffeine supplementation period, participants had fewer benefits in the magnitude of their work compared to the test with the same caffeine dosage initially performed Beaumont et al.

In addition, another recent study Lara et al. The results of the present study showed that chronic caffeine consumption over the stipulated period had an ergogenic effect compared to the placebo condition.

But after 4 days of continuous use of caffeine, the ergogenic effects had a lesser extent when compared to the performance tests in initial caffeine supplementation. In this scenario, chronic caffeine consumption appears to affect improving performance, and it may be necessary to administer acute dosages above those commonly consumed to avoid caffeine tolerance.

This seems to be even more important since studies that pointed to the lack of caffeine tolerance used acute dosages above the participants' usual caffeine consumption Gonçalves et al. Yet, studies that used the same caffeine dosages in acute and in chronic administration indicated less ergogenic caffeine effects after its acute consumption Beaumont et al.

Regardless of the usual intake, this hypothesis needs to be tested. In such cases, the time to develop caffeine tolerance can be a dose-dependent way. Improvement in training-time-dependent physical performance is evidenced in numerous types of exercise.

Studies suggest that anaerobic and aerobic activities may enjoy better yields between and h due to daily variations of the circadian cycle Racinais et al. Since caffeine has been identified as a substance capable of affecting circadian rhythm Narishige et al. The study of Boyett et al. The participants demonstrated performance improvement after caffeine consumption compared to placebo, as well as enhanced results in the morning tests compared to the evening tests.

In the same year, another study Pataky et al. It demonstrated that circadian factors affect the size of improvement after caffeine intake.

Morning caffeine consumption showed improved benefits, compared to the afternoon consumption Pataky et al. In part, caffeine's most significant benefits in the morning may be related to the substance that mitigates performance drops in anaerobic exercises.

This is evidenced by an impaired performance during the morning tests in placebo conditions Chtourou and Souissi, ; Fernandes et al. These effects have been documented in the 3 km time trial test Mora-Rodríguez et al.

Moreover, the acute consumption of moderate dosages of caffeine mg up to 6 h before bedtime disturbed sleep compared to placebo groups Drake et al.

This emphasizes the importance of using caffeine in the morning, aiming at both the better use of performance tests and the maintenance of restful sleep among athletes and active individuals. From this point of view, the existence of possible withdrawal effects drowsiness in the night and the application of caffeine in performance tests with sleep-deprived individuals are points of current discussions that should be explored on performance tests and circadian effects Snel and Lorist, ; Crawford et al.

Through these evidences, caffeine use in the morning can mitigate the unfavorable circadian effects observed in the early phases of the day. Hypothetically, the possible improving performance mediated by caffeine intake may be greater in trained than in untrained individuals, because trained individuals have an improved neuromuscular action potential Yue and Cole, On the other hand, trained individuals have a higher concentration of adenosine A2a receptors than untrained ones Mizuno et al.

Thus, the mechanisms behind different responses seem to be contradictory. To make it even more difficult to understand the possible effects of caffeine-mediated increased performance on different training levels, the current academic literature presents contradictory results in the various types of exercise s proposed Collomp et al.

Some studies suggest greater benefits in trained individuals Collomp et al. Moreover, there are even studies that showed no effect of differences in performance tests related to fitness level O'Rourke et al.

It seems to happen regardless of the type of used test, having unclear findings among studies that have investigated both aerobic O'Rourke et al. Notably, the recent studies by Jodra et al.

The lack of analysis on several mood dimensions related to different fitness status is a limitation of the studies already done Collomp et al. In addition, the majority of the studies do not report the control of habitual caffeine consumption between different training status groups Collomp et al.

This lack of control can result in unclear directions about the real influence of training status mediated by caffeine use on performance. Therefore, the influence of fitness status on improving caffeine performance is not clear. Future studies should try to match the amount of caffeine consumed between different fitness statuses and establish caffeine withdrawal protocols before the performance tests.

Information on the blinding process of supplementation is also well-regarded in future studies since the placebo effect was suggested by one of the studies among different fitness status Brooks et al. The lack of studies involving caffeine in sports performance for women is a topic identified as urgent in future studies Grgic et al.

For instance, in , only One possible explanation is related to the complexity of assessing the effects of caffeine on women since both oral contraceptives Rietveld et al. In these contexts, the alteration in caffeine's metabolism induces differences in the availability of its secondary metabolites paraxanthine and theophylline because the half-life of caffeine in women is greater than in men.

Since these factors are justified for different responsiveness to caffeine in different CYP1A2 polymorphisms for more details, read section CYP1A2 Gene rs g. From this perspective, new studies should investigate the caffeine effects on women. Currently, caffeine's ergogenic effects in aerobic performance tests do not show a gender bias Lane et al.

In contrast, caffeine's ergogenic declines in female anaerobic exercise tests, as reported in some research Sabblah et al. These contradictory results on anaerobic exercises are based, mainly, in a Systematic Review Mielgo-Ayuso et al. In part, gender differences both in delayed onset muscle pain and in the biomarkers under exercise-induced muscle damage have a greater reduction in male than female athletes Chen et al.

The lack of randomized, crossover, placebo-controlled studies comparing male to female groups makes it difficult to interpret the real impact of gender on different performance tests.

This needs to be better explored in future studies considering the realization of training at different times of the day, and investigating the impacts of caffeine withdrawal between women and men in performance tests and sleep.

One of the best accepted theoretical models of caffeine-induced performance improvement is its antagonistic role to adenosine, blocking the adenosine A1 and A2a receptors in the CNS and triggering positive physiological impacts on cognitive ability Daly et al.

Thus, it is plausible to assume that polymorphisms in genes encoding adenosine receptors, such as the adenosine A2a receptor ADORA2A gene, could trigger differentiated reflexes in the metabolic changes induced by the binding of caffeine and its metabolic factors to adenosine receptors, particularly in the CNS.

In this context, Alsene et al. A few years later, Rogers et al. Because the anxiety stimulus can be interpreted both positively Cheng et al.

It is proposed that the acute increase in anxiety pre-exercises or during tests should be analyzed together with the perceived self-confidence of each individual Woodman and Hardy, ; Kais and Raudsepp, In this context, the study carried out by Stavrou et al.

Since it is well-outlined that caffeine can improve the vigor associated with performance Olson et al. Regarding performance tests, Loy et al. In this study, 12 low-active women using oral contraceptives were supplemented with caffeine 5 mg.

More recently, these results were not confirmed by Carswell et al. Among the characteristics that may differ between studies and influence the results e. For example, the study by Loy et al. A single recent study Banks et al. Even not using performance tests, Banks et al.

This could indicate that genetic backgrounds may influence the contradictory effects of caffeine on muscle glucose metabolism glucose uptake and increase muscle glycogen stocks Graham and Spriet, ; Spriet et al.

This hypothesis needs to be tested in further studies involving different doses of caffeine, aerobic exercises, and different carriers to ADORA2A. For more details regarding the possible peripheral effects of caffeine, see section Dosage.

The main enzymes that convert caffeine to its metabolites are those members of the cytochrome P superfamily, mainly the cytochrome P family 1 subfamily A member 2 CYP1A2 Nehlig, It was portrayed that a genetic polymorphism in intron 1 of the CYP1A2 gene rs could be responsible for a differentiated regulation of the caffeine to its secondary metabolites i.

In these cases, it is pointed out that the secondary metabolites of caffeine paraxanthine and theophylline have a higher affinity of binding to adenosine receptors than caffeine itself Daly et al.

Since the binding of caffeine to adenosine receptors justifies the use of the substance in sports Figure 1A , individuals with different rates of paraxanthine and theophylline production via polymorphisms for the CYP1A2 gene have been investigated in performance tests.

Because of these relevant findings, Womack et al. This study was the first to show different CYP1A2 genotypic responses to caffeine supplementation on exercise performance, demonstrating that genetic variability could be, in fact, one of the factors correlated with different caffeine responsiveness.

Both the degree of training and the habitual caffeine consumption were pointed out in previous studies as possible confusing characteristics of caffeine administration on sports performance see sections Habitual Caffeine Consumption and Degree of Training. In agreement, Guest et al. In this study Guest et al.

This study Guest et al. Other studies have analyzed the effects of CYP1A2 polymorphism in aerobic performance tests with mixed samples men and women , indicating contradictory results Algrain et al.

Algrain et al. In opposition Carswell et al. Aspects such as non-adjustment of dosage by body weight, the absence of caffeine ergogenic response and the administration of caffeine in alternative forms are limitations in the study of Algrain et al. There is currently good evidence Womack et al.

In intermittent activities, Klein et al. After ingestion of caffeine 6 mg. This finding is in agreement with Puente et al. Until the present moment, there is no evidence of correlation between the CYP1A2 polymorphism and intermittent exercise performance. However, it should be noted that in both studies there was a low total number of participants 16 and 19 subjects and the inclusion of different genders in the same analysis.

Moreover, there were differences in the exercise protocol, which can hinder a true understanding of the CYP1A2 genotypic influence on intermittent exercises. In anaerobic modalities, Giersch et al.

Nevertheless, there was a more pronounced increase in serum caffeine among C-allele carriers ± Another study Salinero et al. and after the ingestion of caffeine 3 mg.

The results indicate that the caffeine intake increased the peak power ± W vs. These appointments were again confirmed by Grgic et al. Thus, there is no evidence that different genotyping for CYP1A2 can mediate increased performance from caffeine use in short duration, high-intensity exercises, at least in the doses used 3—6 mg.

Studies using larger samples and evaluating other doses are welcome before drawing more solid conclusions. In addition to Wingate tests, Grgic et al. As caffeine's effects on strength training still appear to be unclear in the literature see section Dosage , it is surprising that the increase in muscle performance is documented, especially in the dosages used 3 mg.

As there is a documented increase in strength in a dose-dependent manner with the use of caffeine Pallarés et al. This becomes even more interesting since Rahimi demonstrated that supplementation of moderate doses of caffeine 6 mg.

In conclusion, the ergogenic or ergolitic effects from caffeine use may be influenced by factors related to caffeine effects, daily habits, physiological factors, and genetic factors Figure 2.

Figure 2. Main factors that could be involved in the ergogenic or ergolitic effects of caffeine supplementation applied to physical exercises.

The image represents the variables related to the use of caffeine, such as the applied dosage, ingestion time, and caffeine withdrawal effects.

Daily habits such as habitual consumption of food and beverage sources of caffeine and time of training should also be considered. Physiological Factors gender and degree of training and genetic factors related to the structures of adenosine receptors in the CNS ADORA2A and hepatic enzymes related to caffeine degradation CYP1A2 are new findings that should be of relevant consideration for the elucidation of inter-individual responses to caffeine on exercise performance.

In this context, caffeine's effects enable improvements in exercise performance on a wide dosage range 2—9 mg. This is curious, since the physiological mechanisms involved in increasing the dosage are not clear.

In part, habitual consumption and the time of day when caffeine is ingested may or not diminish the benefits of the substance, however, this does not explain the worsening in the performance observed among some individuals. Possible explanations have been formulated signaling genetic influences related to the CYP1A2 and ADORA2A gene polymorphisms.

Noteworthy, intermittent and anaerobic exercises seem not to have different responses related to the CPY1A2 polymorphism. However, the low number of studies and the fact that current approaches have a low number of participants is an important limitation that should be overcome in future studies.

Another point related to the lack of results may be the time of caffeine ingestion before conducting short tests Pickering, In these cases, it is pointed out that caffeine supplementation is also ergogenic when consumed 1—3 h before exercise Bell and McLellan, In addition, physical characteristics degree of training and gender , caffeine withdrawal, and possible influences related to the ADORA2A gene polymorphism present unclear results in the current academic literature.

AL and GM were responsible for the conception of this present work. GM, JG, and AL drafted the manuscript. GM created the images. TS-J, LF, and AL reviewed and made significant contributions to the manuscript.

All authors approved the final version of this manuscript. GM is supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior CAPES , Financial Support: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Abernethy, D. Impairment of caffeine clearance by chronic use of low-dose oestrogen-containing oral contraceptives. doi: PubMed Abstract CrossRef Full Text Google Scholar. Aguilar-Navarro, M. Urine caffeine concentration in doping control samples from to Nutrients Algrain, H.

The effects of a polymorphism in the cytochrome P CYP1A2 gene on performance enhancement with caffeine in recreational cyclists. Caffeine Res. CrossRef Full Text Google Scholar. Ali, A. The effect of caffeine ingestion during evening exercise on subsequent sleep quality in females.

Sports Med. Alsene, K. Association between A 2a receptor gene polymorphisms and caffeine-induced anxiety. Neuropsychopharmacology 28, — Anderson, M. Improved meter rowing performance in competitive oarswomen after caffeine ingestion. Sport Nutr. Areta, J.

Inaccuracies in caffeine intake quantification and other important limitations in recent publication by Gonçalves et al. Astorino, T. Effect of caffeine ingestion on one-repetition maximum muscular strength.

Azevedo, R. Effects of caffeine ingestion on endurance performance in mentally fatigued individuals. Banks, N. Genetic polymorphisms in ADORA2A and CYP1A2 influence caffeine's effect on postprandial glycaemia.

Battram, D. Caffeine ingestion does not impede the resynthesis of proglycogen and macroglycogen after prolonged exercise and carbohydrate supplementation in humans.

Beaumont, R. Chronic ingestion of a low dose of caffeine induces tolerance to the performance benefits of caffeine. Sports Sci. Behrens, M. Caffeine-induced increase in voluntary activation and strength of the quadriceps muscle during isometric, concentric and eccentric contractions.

Bell, D. Exercise endurance 1, 3, and 6 h after caffeine ingestion in caffeine users and nonusers. Boulenger, J. Chronic caffeine consumption increases the number of brain adenosine receptors. Life Sci. Boyett, J. Time of day and training status both impact the efficacy of caffeine for short duration cycling performance.

Brooks, J. Acute effects of caffeine on strength performance in trained and untrained individuals. CrossRef Full Text.

Bruce, C. Enhancement of m rowing performance after caffeine ingestion. Sports Exerc. Carswell, A. The effect of caffeine on cognitive performance is influenced by CYP1A2 but not ADORA2A genotype, yet neither genotype affects exercise performance in healthy adults.

Cesareo, K. The effects of a caffeine-like supplement, TeaCrine®, on muscular strength, endurance and power performance in resistance-trained men. Sports Nutr. Chen, H. Effects of caffeine and sex on muscle performance and delayed-onset muscle soreness after exercise-induced muscle damage: a double-blind randomized trial.

Effects of gender difference and caffeine supplementation on anaerobic muscle performance. Cheng, W. Predictive validity of a three-dimensional model of performance anxiety in the context of tae-kwon-do.