Caffeine pills for athletic performance -
Navy Seals. The positive effects of caffeine on cognitive function were further supported by work from Kamimori et al. The caffeine intervention maintained psychomotor speed, improved event detection, increased the number of correct responses to stimuli, and increased response speed during logical reasoning tests.
Under similar conditions of sleep deprivation, Tikuisis et al. When subjects are not sleep deprived, the effects of caffeine on cognition appear to be less effective. For example, Share et al. In addition to the ability of caffeine to counteract the stress from sleep deprivation, it may also play a role in combatting other stressors.
Gillingham et al. However, these benefits were not observed during more complex operations [ ]. Crowe et al. Again, no cognitive benefit was observed. Other studies [ , , , ] support the effects of caffeine on the cognitive aspects of sport performance, even though with some mixed results [ , ].
Foskett et al. This was supported by Stuart et al. firefighting, military related tasks, wheelchair basketball [ ].
The exact mechanism of how caffeine enhances cognition in relation to exercise is not fully elucidated and appears to work through both peripheral and central neural effects [ ]. In a study by Lieberman et al.
Repeated acquisition are behavioral tests in which subjects are required to learn new response sequences within each experimental session [ ].
The researchers [ 42 ] speculated that caffeine exerted its effects from an increased ability to sustain concentration, as opposed to an actual effect on working memory. Other data [ ] were in agreement that caffeine reduced reaction times via an effect on perceptual-attentional processes not motor processes.
This is in direct contrast to earlier work that cited primarily a motor effect [ ]. Another study with a sugar free energy drink showed similar improvements in reaction time in the caffeinated arm; however, they attributed it to parallel changes in cortical excitability at rest, prior, and after a non-fatiguing muscle contraction [ ].
The exact cognitive mechanism s of caffeine have yet to be elucidated. Based on some of the research cited above, it appears that caffeine is an effective ergogenic aid for individuals either involved in special force military units or who may routinely undergo stress including, but not limited to, extended periods of sleep deprivation.
Caffeine in these conditions has been shown to enhance cognitive parameters of concentration and alertness. It has been shown that caffeine may also benefit sport performance via enhanced passing accuracy and agility. However, not all of the research is in agreement.
It is unlikely that caffeine would be more effective than actually sleeping, i. Physical activity and exercise in extreme environments are of great interest as major sporting events e.
Tour de France, Leadville , Badwater Ultramarathon are commonly held in extreme environmental conditions. Events that take place in the heat or at high altitudes bring additional physiological challenges i.
Nonetheless, caffeine is widely used by athletes as an ergogenic aid when exercising or performing in extreme environmental situations. Ely et al. Although caffeine may induce mild fluid loss, the majority of research has confirmed that caffeine consumption does not significantly impair hydration status, exacerbate dehydration, or jeopardize thermoregulation i.
Several trials have observed no benefit of acute caffeine ingestion on cycling and running performance in the heat Table 2 [ , , ]. It is well established that caffeine improves performance and perceived exertion during exercise at sea level [ , , , ].
Despite positive outcomes at sea level, minimal data exist on the ergogenic effects or side effects of caffeine in conditions of hypoxia, likely due to accessibility of this environment or the prohibitive costs of artificial methods.
To date, only four investigations Table 3 have examined the effects of caffeine on exercise performance under hypoxic conditions [ , , , ]. Overall, results to date appear to support the beneficial effects of caffeine supplementation that may partly reduce the negative effects of hypoxia on the perception of effort and endurance performance [ , , , ].
Sources other than commonly consumed coffee and caffeine tablets have garnered interest, including caffeinated chewing gum, mouth rinses, aerosols, inspired powders, energy bars, energy gels and chews, among others.
While the pharmacokinetics [ 18 , , , , ] and effects of caffeine on performance when consumed in a traditional manner, such as coffee [ 47 , 49 , 55 , , , , ] or as a caffeine capsule with fluid [ 55 , , , ] are well understood, curiosity in alternate forms of delivery as outlined in pharmacokinetics section have emerged due to interest in the speed of delivery [ 81 ].
A recent review by Wickham and Spriet [ 5 ] provides an overview of the literature pertaining to caffeine use in exercise, in alternate forms. Therefore, here we only briefly summarize the current research. Several investigations have suggested that delivering caffeine in chewing gum form may speed the rate of caffeine delivery to the blood via absorption through the extremely vascular buccal cavity [ 58 , ].
Kamimori and colleagues [ 58 ] compared the rate of absorption and relative caffeine bioavailability from caffeinated chewing gum and caffeine in capsule form.
The results suggest that the rate of drug absorption from the gum formulation was significantly faster.
These findings suggest that there may be an earlier onset of pharmacological effects from caffeine delivered through the gum formulation. Further, while no data exist to date, it has been suggested that increasing absorption via the buccal cavity may be preferential over oral delivery if consumed closer to or during exercise, as splanchnic blood flow is often reduced [ ], potentially slowing the rate of caffeine absorption.
To date, five studies [ 59 , 60 , 61 , 62 , 63 ] have examined the potential ergogenic impact of caffeinated chewing gum on aerobic performance, commonly administered in multiple sticks Table 4. To note, all studies have been conducted using cycling interventions, with the majority conducted in well-trained cyclists.
However, more research is needed, especially in physically active and recreationally training individuals. Four studies [ 64 , 66 , 68 , ] have examined the effect of caffeinated chewing gum on more anaerobic type activities Table 4.
Specifically, Paton et al. The reduced fatigue in the caffeine trials equated to a 5. Caffeinated gum consumption also positively influenced performance in two out of three soccer-specific Yo-Yo Intermittent Recovery Test and CMJ tests used in the assessment of performance in soccer players [ 66 ].
These results suggest that caffeine chewing gums may provide ergogenic effects across a wide range of exercise tasks. To date, only Bellar et al. Future studies may consider comparing the effects of caffeine in chewing gums to caffeine ingested in capsules.
Specifically, the mouth contains bitter taste sensory receptors that are sensitive to caffeine [ ]. It has been proposed that activation of these bitter taste receptors may activate neural pathways associated with information processing and reward within the brain [ , , ].
Physiologically, caffeinated mouth rinsing may also reduce gastrointestinal distress potential that may be caused when ingesting caffeine sources [ , ]. Few investigations on aerobic [ 69 , 74 , 75 , 76 , ] and anaerobic [ 72 , 73 , 78 ] changes in performance, as well as cognitive function [ 70 , 71 ] and performance [ 77 ], following CMR have been conducted to date Table 5.
One study [ ] demonstrated ergogenic benefits of CMR on aerobic performance, reporting significant increases in distance covered during a min arm crank time trial performance. With regard to anaerobic trials, other researchers [ 72 ] have also observed improved performance, where recreationally active males significantly improved their mean power output during repeated 6-s sprints after rinsing with a 1.
While CMR has demonstrated positive outcomes for cyclists, another study [ 78 ] in recreationally resistance-trained males did not report any significant differences in the total weight lifted by following a 1. CMR appears to be ergogenic in cycling to include both longer, lower-intensity and shorter high-intensity protocols.
The findings on the topic are equivocal likely because caffeine provided in this source does not increase caffeine plasma concentration and increases in plasma concentration are likely needed to experience an ergogenic effect of caffeine [ 69 ].
Details of these studies, as well as additional studies may be found in Table 5. The use of caffeinated nasal sprays and inspired powders are also of interest. Three mechanisms of action have been hypothesized for caffeinated nasal sprays. Firstly, the nasal mucosa is permeable, making the nasal cavity a potential route for local and systemic substance delivery; particularly for caffeine, a small molecular compound [ 11 , 12 , 30 , 31 ].
Secondly, and similar to CMR, bitter taste receptors are located in the nasal cavity. The use of a nasal spray may allow for the upregulation of brain activity associated with reward and information processing [ ].
Thirdly, but often questioned due to its unknown time-course of action, caffeine could potentially be transported directly from the nasal cavity to the CNS, specifically the cerebrospinal fluid and brain by intracellular axonal transport through two specific neural pathways, the olfactory and trigeminal [ , ].
No significant improvements were reported in either anaerobic and aerobic performance outcome measures despite the increased activity of cingulate, insular, and sensory-motor cortices [ 79 ]. Laizure et al. Both were found to have similar bioavailability and comparable plasma concentrations with no differences in heart rate or blood pressure Table 6.
While caffeinated gels are frequently consumed by runners, cyclists and triathletes, plasma caffeine concentration studies have yet to be conducted and only three experimental trials have been reported.
Cooper et al. In the study by Cooper et al. In contrast, Scott et al. utilized a shorter time period from consumption to the start of the exercise i. However, these ideas are based on results from independent studies and therefore, future studies may consider exploring the optimal timing of caffeine gel ingestion in the same group of participants.
More details on these studies may be found in Table 7. Similar to caffeinated gels, no studies measured plasma caffeine concentration following caffeinated bar consumption; however, absorption and delivery likely mimic that of coffee or caffeine anhydrous capsule consumption.
While caffeinated bars are commonly found in the market, research on caffeinated bars is scarce. To date, only one study [ 82 ] Table 7 has examined the effects of a caffeine bar on exercise performance.
Furthermore, cyclists significantly performed better on complex information processing tests following the time trial to exhaustion after caffeine bar consumption when compared to the carbohydrate only trial.
As there is not much data to draw from, future work on this source of caffeine is needed. A review by Trexler and Smith-Ryan comprehensively details research on caffeine and creatine co-ingestion [ 32 ]. With evidence to support the ergogenic benefits of both creatine and caffeine supplementation on human performance—via independent mechanisms—interest in concurrent ingestion is of great relevance for many athletes and exercising individuals [ 32 ].
While creatine and caffeine exist as independent supplements, a myriad of multi-ingredient supplements e. It has been reported that the often-positive ergogenic effect of acute caffeine ingestion prior to exercise is unaffected by creatine when a prior creatine loading protocol had been completed by participants [ , ].
However, there is some ambiguity with regard to the co-ingestion of caffeine during a creatine-loading phase e. While favorable data exist on muscular performance outcomes and adaptations in individuals utilizing multi-ingredient supplements e.
Until future investigations are available, it may be prudent to consume caffeine and creatine separately, or avoid high caffeine intakes when utilizing creatine for muscular benefits [ ]. This is likely due to the heterogeneity of experimental protocols that have been implemented and examined.
Nonetheless, a systematic review and meta-analysis of 21 investigations [ ] concluded the co-ingestion of carbohydrate and caffeine significantly improved endurance performance when compared to carbohydrate alone.
However, it should be noted that the magnitude of the performance benefit that caffeine provides is less when added to carbohydrate i. carbohydrate than when isolated caffeine ingestion is compared to placebo [ ]. Since the publication [ ], results remain inconclusive, as investigations related to sport-type performance measures [ 83 , , , , , , ], as well as endurance performance [ 84 , , ] continue to be published.
Overall, to date it appears caffeine alone, or in conjunction with carbohydrate is a superior choice for improving performance, when compared to carbohydrate supplementation alone. Few studies to date have investigated the effect of post-exercise caffeine consumption on glucose metabolism [ , ].
While the delivery of exogenous carbohydrate can increase muscle glycogen alone, Pedersen et al. In addition, it has been demonstrated that co-ingestion of caffeine with carbohydrate after exercise improved subsequent high-intensity interval-running capacity compared with ingestion of carbohydrate alone.
This effect may be due to a high rate of post-exercise muscle glycogen resynthesis [ ]. Practically, caffeine ingestion in close proximity to sleep, coupled with the necessity to speed glycogen resynthesis, should be taken into consideration, as caffeine before bed may cause sleep disturbances.
The genus of coffee is Coffea , with the two most common species Coffea arabica arabica coffee and Coffea canephora robusta coffee used for global coffee production. While coffee is commonly ingested by exercising individuals as part of their habitual diet, coffee is also commonly consumed pre-exercise to improve energy levels, mood, and exercise performance [ 11 , 40 ].
Indeed, a recent review on coffee and endurance performance, reported that that coffee providing between 3 and 8. Specifically, Higgins et al. Since the release of the Higgins et al.
review, three additional studies have been published, examining the effects of coffee on exercise performance. Specifically, Niemen et al. Fifty-km cycling time performance and power did not differ between trials. Regarding resistance exercise performance, only two studies [ 55 , 56 ] have been conducted to date.
One study [ 56 ] reported that coffee and caffeine anhydrous did not improve strength outcomes more than placebo supplementation. On the other hand, Richardson et al. The results between studies differ likely because it is challenging to standardize the dose of caffeine in coffee as differences in coffee type and brewing method may alter caffeine content [ ].
Even though coffee may enhance performance, due to the difficulty of standardizing caffeine content most sport dietitians and nutritionists use anhydrous caffeine with their athletes due to the difficulty of standardizing caffeine content.
Consumption of energy drinks has become more common in the last decade, and several studies have examined the effectiveness of energy drinks as ergogenic aids Table 8. Souza and colleagues [ ] completed a systematic review and meta-analysis of published studies that examined energy drink intake and physical performance.
Studies including endurance exercise, muscular strength and endurance, sprinting and jumping, as well as sport-type activities were reviewed. It has been suggested that the additional taurine to caffeine containing energy drinks or pre-workout supplements, as well as the addition of other ergogenic supplements such as beta-alanine, B-vitamins, and citrulline, may potentiate the effectiveness of caffeine containing beverages on athletic performance endeavors [ ].
However, other suggest that the ergogenic benefits of caffeine containing energy drinks is likely attributed to the caffeine content of the beverage [ ].
For a thorough review of energy drinks, consider Campbell et al. Table 8 provides a review of research related to energy drinks and pre-workout supplements. Caffeine in its many forms is a ubiquitous substance frequently used in military, athletic and fitness populations which acutely enhance many aspects of exercise performance in most, but not all studies.
Supplementation with caffeine has been shown to acutely enhance many aspects of exercise, including prolonged aerobic-type activities and brief duration, high-intensity exercise.
The optimal timing of caffeine ingestion likely depends on the source of caffeine. Studies that present individual participant data commonly report substantial variation in caffeine ingestion responses. Inter-individual differences may be associated with habitual caffeine intake, genetic variations, and supplementation protocols in a given study.
Caffeine may be ergogenic for cognitive function, including attention and vigilance. Caffeine at the recommended doses does not appear significantly influence hydration, and the use of caffeine in conjunction with exercise in the heat and at altitude is also well supported.
Alternative sources of caffeine, such as caffeinated chewing gum, mouth rinses, and energy gels, have also been shown to improve performance. Energy drinks and pre-workouts containing caffeine have been demonstrated to enhance both anaerobic and aerobic performance.
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Pharmacokinetic analysis and comparison of caffeine administered rapidly or slowly in coffee chilled or hot versus chilled energy drink in healthy young adults.
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Comparison of cytochrome P CYP genes from the mouse and human genomes, including nomenclature recommendations for genes, pseudogenes and alternative-splice variants. Begas E, Kouvaras E, Tsakalof A, Papakosta S, Asprodini EK. In vivo evaluation of CYP1A2, CYP2A6, NAT-2 and xanthine oxidase activities in a Greek population sample by the RP-HPLC monitoring of caffeine metabolic ratios.
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Djordjevic N, Ghotbi R, Jankovic S, Aklillu E. Ghotbi R, Christensen M, Roh HK, Ingelman-Sundberg M, Aklillu E, Bertilsson L. Comparisons of CYP1A2 genetic polymorphisms, enzyme activity and the genotype-phenotype relationship in Swedes and Koreans. Perera V, Gross AS, McLachlan AJ.
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Induction of CYP1A2 by heavy coffee consumption in Serbs and Swedes. Marks V, Kelly JF. Absorption of caffeine from tea, coffee, and coca cola. Liguori A, Hughes JR, Grass JA. Absorption and subjective effects of caffeine from coffee, cola and capsules. Pharmacol Biochem Behav. Shargel LYA.
Applied biopharmaceutics and pharmacokinetics. Stamford: Appleton and Lange; Rousseau E, Ladine J, Liu QY, Meissner G. Arch Biochem Biophys. Tarnopolsky M, Cupido C. Caffeine potentiates low frequency skeletal muscle force in habitual and nonhabitual caffeine consumers. Kalmar JM, Cafarelli E. Caffeine: a valuable tool to study central fatigue in humans?
Exerc Sport Sci Rev. Meeusen R, Roelands B, Spriet LL. Caffeine, exercise and the brain. Nestle Nutr Inst Workshop Ser. Nehlig A, Daval JL, Debry G. Caffeine and the central nervous system: mechanisms of action, biochemical, metabolic and psychostimulant effects. 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.
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Caffeine performxnce are often associated with Antispasmodic Techniques for Migraines and late-night studying. However, there are a variety of lesser known, Bone density exercises surprisingly useful, benefits athleitc supplementing with caffeine. Read on to discover how to safely implement Caffeine pills for athletic performance supplements into petformance routine, performznce Caffeine pills for athletic performance physical and mental performance. Caffeine is a stimulant that acts on the central nervous system, or the brain, spinal cord and nerves, to make an individual feel more alert and focused. It mimics adenosine in structure, and binds to adenosine receptors to reduce the amount of this neurotransmitter reaching the brain. Naturally, caffeine can be found in a variety of foods and beverages, such as tea and coffee. Within a supplement, caffeine can come in natural or synthetic form, and often contains between mg of caffeine.
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