Studies have shown improvements in vigilance and attention. Based on an a priori power analysis done using G*Power software (version 3.1; Germany, Dusseldorf) for repeated-measures Analysis of Variance (ANOVA) (within-between interaction, i.e., in the context of this study genotype × caffeine interaction), with an assumed true effect size f of 0.25, the alpha error level of 0.05, and the expected correlation between repeated measures of 0.75, the required sample size to achieve the statistical power of 80% for this study was 18 participants. Therefore, it could be argued that the findings of the meta-analysis should primarily be generalized to these doses of caffeine. The acute improvement in vertical jump height following caffeine ingestion is comparable to the improvement in jump height found as a result of 4 weeks of plyometric training [39, 40]. Sabol F, Grgic J, Mikulic P. The effects of 3 different doses of caffeine on jumping and throwing performance: a randomized, double-blind, crossover study. CYP1A2 genotype should be considered when deciding whether … Pallarés JG, Fernández-Elías VE, Ortega JF, Muñoz G, Muñoz-Guerra J, Mora-Rodríguez R. Neuromuscular responses to incremental caffeine doses: performance and side effects. 2017;27:1240–7. PLoS One. The purpose of this study was to investigate whether variations in 163 C > A CYP1A2 genotypes (rs 762 551) (AA, AC, and CC) modify the ergogenic effects of caffeine (CAF) on strength, power, muscular endurance, agility, and endurance in adolescent athletes.. Methods. Assessment of blinding in clinical trials. Scand J Med Sci Sports. Additionally, 25 mL of 1.14% caffeine or placebo solution were mouth rinsed before each TT. 2019;11:E937. If you are struggling with focus or sleep quality, take a look at your caffeine genes in your. Inter-individual variation in caffeine ergogenicity, and a move towards personalised sports nutrition. The samples were analyzed for the CYP1A2 rs762551 single-nucleotide polymorphism. In the present study, we found that the ESs were very similar for both mean and peak velocity, and this was a constant finding across all the employed loads (i.e., 25 to 90% of 1RM). Participants were asked not to perform any strenuous exercise for at least 24 hours before the main trials. Guest et al. Exercise performance was assessed with the following outcomes: (a) movement velocity and power output in the bench press exercise with loads of 25, 50, 75, and 90% of one-repetition maximum (1RM); (b) quality and quantity of performed repetitions in the bench press exercise performed to muscular failure with 85% 1RM; (c) vertical jump height in a countermovement jump test; and (d) power output in a Wingate test. This approach allowed us to objectively quantify the average quality of the repetitions during the test and examine if caffeine ingestion had an effect on movement velocity and power output when the total number of repetitions was matched. When the mean velocity of a successful 1RM attempt reached these values, the load was considered as a valid estimate of the 1RM [17]. It is the main enzyme that breaks down caffeine. Induction of CYP1A2 by heavy coffee consumption is associated with the, Sachse, C., Brockmöller, J., Bauer, S., & Roots, I. Studies have shown that taking caffeine before exercise improves performance. To get around 10 to 12 participants with the CC genotype a study would need to screen from 100 to 120 potential study participants. The gene CYP1A2 encodes cytochrome P450 1A2, an enzyme responsible for up to 95% of caffeine metabolism [8]. 2018;18:219–25. Among these, clozapine, olanzapine, thoephylline, and tizandine are important. The placebo capsule was identical in appearance to the caffeine capsule, but, instead of caffeine, it contained 3 mg/kg of dextrose. The C allele is considered the wild-type, even though it is the rarer allele in most populations. 2013;45:2184–92. This study adds to the body of evidence showing improvements in muscle endurance following caffeine ingestion [28,29,30,31,32]. U.S. National Library of Medicine. To factor in possible dropouts, we recruited 22 participants. Eur J Sport Sci. The participants arrived at the laboratory following overnight fasting. 1999;47:445–9. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. On average, individuals with the AA genotype were able to complete one more repetition with the consumption of caffeine, as compared to placebo, whereas the number of repetitions was the same in the placebo and caffeine conditions among those with the AC/CC genotypes. Int J Sports Physiol Perform. Studies that have reported individual participant data suggest that some individuals experience an increase in performance following caffeine ingestion, whereas others do not [4,5,6]. Koonrungsesomboon N, Khatsri R, Wongchompoo P, Teekachunhatean S. The impact of genetic polymorphisms on CYP1A2 activity in humans: a systematic review and meta-analysis. Caffeine is used to treat headaches, improve mental alertness and enhance physical performance. Ernährungs Umschau. The comparisons of the effects of caffeine on exercise performance between individuals with the AA genotype and AC/CC genotypes found no significant differences. CYP1A2 breaks down toxins, drugs, hormones, and metabolic waste products. All participants completed all testing procedures and were included in the final analysis. Polito MD, Souza DB, Casonatto J, Farinatti P. Acute effect of caffeine consumption on isotonic muscular strength and endurance: a systematic review and meta-analysis. National Institutes of Health; Available from: https://ghr.nlm.nih.gov/primer/genefamily/cytochromep450. Google Scholar. Sports Med. The *1F variant is well-studied, but is not the only gene that affects caffeine metabolism. The wild type (or the most common variant) CYP1A2 polymorphism is CYP1A2*1A. Br J Clin Pharmacol. These sessions were the same as the main sessions (i.e., placebo and caffeine sessions), with the exception that the first one included one-repetition maximum (1RM) testing in the bench press exercise. However, for high-intensity exercise tasks of a shorter duration, the evidence is less clear. The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. Neurosci Biobehav Rev. 2019;49:17–30. The speed of caffeine metabolism is affected by a single nucleotide polymorphism, rs762551, within this gene [8]. Caffeine acts to block adenosine receptors which in turn stimulate the central nervous system. 1992;2:73–7. CC, AC = CYP1A2*1C = Slow Metabolizer. 2007;41:349–55. Cite this article. The two main sessions (i.e., caffeine and placebo sessions) were conducted in a randomized and counterbalanced order. Pharmacogenet Genomics. Tallis and colleagues [43] tested their participants in four conditions: (1) “told caffeine, given caffeine”; (2) “told caffeine, given placebo”; (3) “told placebo, given placebo”; and (4) “told placebo, given caffeine”. Google Scholar. DNA was extracted and purified using the Isohelix Buccalyse DNA extraction kit BEK-50 (Cell Projects Ltd., Kent, UK), and amplified through polymerase chain reaction (PCR) on an ABI 7900 real-time thermocycler (Applied Biosystem, Waltham, USA). Wake up and smell the coffee: caffeine supplementation and exercise performance—an umbrella review of 21 published meta-analyses. 3.2.8.4 CYP1A2. Effect of caffeine ingestion on muscular strength and endurance: a meta-analysis. All participants attended four laboratory sessions. 2017;17:1029–36. In order to assist with caffeine restriction, we provided the participants with a list of the most common foods and drinks that contain caffeine. Previous research has established that this device has good test-retest reliability for power and velocity outcomes in the bench press [19]. How the body metabolises caffeine . A (C/A) single nucleotide polymorphism at intron 1 of the cytochrome P450 (CYP1A2) gene influences caffeine metabolism and clinical outcomes from caffeine ingestion. Nutrients. Grgic J, Trexler ET, Lazinica B, Pedisic Z. CYP1A2 is an enzyme responsible for the metabolism of caffeine and some drugs. Sci Sports. rs762551, also known as -164A>C or -163C>A, is a SNP encoding the CYP1A2*1F allele of the CYP1A2 gene. 2019. https://doi.org/10.1007/s40279-019-01211-9. 2009;23:1363–9. [18]. The significance level was set at p <  0.05. Fast metabolizers of caffeine may have a high caffeine tolerance. Bloms LP, Fitzgerald JS, Short MW, Whitehead JR. The objective of this study was to determine whether variation in the CYP1A2 gene, which affects caffeine metabolism, modifies the ergogenic effects of caffeine in a 10-km cycling time trial. Jozo Grgic. AA are fast caffeine metabolizers. The Wingate test was performed using a Lode Excalibur Sport Cycle Ergometer (The Netherlands, Groningen). The exclusion criteria were: (i) prior use of anabolic steroids; and (ii) the existence of any health limitations. It has been suggested that polymorphisms within CYP1A2 impact inter-individual variation in the response to caffeine. Two studies [11, 12] that explored the effects of caffeine on jumping and Wingate test performance reported similar improvements in these outcomes following the ingestion of 3 mg/kg of caffeine in groups of participants with the AA and AC/CC genotypes. It should be noted that the increased cognitive benefits are seen more in those who are tired. Neurosci Biobehav Rev. 2012;9:7. Int J Sports Med. The participants performed a CMJ on a force platform (400S Isotronic Fitness Technology, Skye, South Australia, Australia). Guest N, Corey P, Vescovi J, El-Sohemy A. Caffeine, CYP1A2 genotype, and endurance performance in athletes. Orange ST, Metcalfe JW, Marshall P, Vince RV, Madden LA, Liefeith A. Test-retest reliability of a commercial linear position transducer (GymAware PowerTool) to measure velocity and power in the back squat and bench press. In the current study, we could not test this further, because the number of individuals with the CC genotype was n = 2. 85% of Americans consume a caffeinated beverage daily, averaging about 165 mg per day. Caffeine ingestion resulted in increased vertical jump height in the CMJ. Improvements in squat strength were similar for both training conditions, even though the group that trained with a velocity loss of 20% performed 40% fewer repetitions. He received no financial incentives for the preparation of this manuscript. The participants underwent genetic testing using a commercially available testing kit from DNAfit Life Sciences (London, UK), as in other studies [25]. Resistance-trained men may experience acute improvements in resistance exercise, jumping, and sprinting performance following the ingestion of caffeine. Functional significance of a C→A polymorphism in intron 1 of the cytochrome P450 CYP1A2 gene tested with caffeine. We opted to utilize a lower dose of caffeine as higher doses of caffeine do not seem to produce greater increases in performance [28]. PLoS One. Mary F. Hebert, in Clinical Pharmacology During Pregnancy, 2013. Craig Pickering is a former employee of DNAFit Ltd., a genetic testing company. Mayo Clinic. Certain drugs can induce or inhibit the enzyme, affecting the metabolism of drugs that use the same pathway. The ESs, favoring caffeine conditions in all outcomes, ranged from 0.20 to 0.29 for all outcomes recorded at 25% 1RM, from 0.21 to 0.23 for all outcomes at 50% 1RM, from 0.31 to 0.50 for all outcomes at 75% 1RM, and from 0.57 to 0.61 for outcomes at 90% 1RM. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. 2014;61:58–63. The effect of caffeine on exercise performance has been thoroughly documented in a variety of activities.1–4 A proposed mechanism for caffeine's ergogenic effect is adenosine receptor blockade. One well known substrate of CYP1A2 is caffeine; individuals who carry one or more CYP1A2*1C alleles are "slow" caffeine metabolizers, whereas carriers of the variant CYP1A2*1F are "fast" caffeine metabolizers.The same amount of caffeine will therefore tend to have … While adenosine decreases neuronal firing and arousal, caffeine binds to adenosine receptors, thus limiting the aforementioned adenosine responses.5 It has also been suggested that caffeine metabolites paraxanthine (PX), theobromine (TB), and theophylline (TP) have an even higher affinity for adenosine … JG performed the experiments, analyzed the data, and wrote the first draft. In addition to caffeine, CYP1A2 breaks down several prescription medications (substrates). 2016 Dec;71:294-312. California Privacy Statement, For example, smoking will induce CYP1A2, which will speed up the metabolism of caffeine. The research was performed in accordance with the Declaration of Helsinki. The *1F variant is well-studied, but is not the only gene that affects caffeine metabolism. Besides the total number of repetitions, we also measured velocity and power output for each repetition using the linear position transducer attached to the barbell. Three minutes were allowed between 1RM attempts. Genetics of Caffeine Consumption. For the maximum number of repetitions in the bench press exercise with 85% 1RM, we did not find a significant main effect for genotype (p = 0.397) or a genotype × caffeine interaction effect (p = 0.454), while there was a significant main effect favoring caffeine (p <  0.001; ES = 0.53). The results reported herein are generally in line with the current body of evidence. For this study, we reported the data from this index as a percentage of individuals who identified the correct treatment condition beyond chance [19, 26]. CYP1A2 is involved in the metabolism of fewer drugs than the enzymes previously discussed. Each repetition was followed by a 3-min rest interval. ID: ACTRN12619000885190. Both in the caffeine and the placebo trials, before and after the exercise session, participants responded to the following question: “Which supplement do you think you have ingested?” [24]. Even though the improvement in performance was relatively small (approximately 1 cm), it might still be practically meaningful in sports where jump height directly impacts athletic outcomes. We did not find significant genotype × caffeine interaction effects in any of the analyzed performance variables. The researchers also noted that the effects of caffeine on mean velocity (ES = 0.80) were higher than those for peak velocity (ES = 0.41) [27]. After the rest interval, muscle endurance was assessed with a test that involved performing repetitions to momentary muscle failure with a load corresponding to 85% of 1RM in the bench press exercise, as in the study by Rahimi [13]. Conversely, research has found people with the C allele are slow caffeine metabolizers meaning it takes their body longer to break down caffeine which can lead to a stronger response to caffeine. To systematically review studies that examined the influence of the CYP1A2 −163C>A polymorphism on the ergogenic effects of caffeine and to discuss some of the reasons for the discrepancies in findings between the studies. Prior to the study, the trial was registered in the Australian New Zealand Clinical Trials Registry ID: ACTRN12619000885190. The CYP1A2 gene encodes a member of the cytochrome p450 family of proteins, which metabolize nutrients and drugs. Specifically, when matching the number of repetitions between conditions, we found that the effects of caffeine, as compared to placebo, amounted to 0.27 for peak power, 0.51 for peak velocity, 0.53 for mean power, and 0.85 for mean velocity. Induction of CYP1A2 by heavy coffee consumption is associated with the CYP1A2 −163C>A polymorphism. 2016;33:361–6. Several genes are involved in eliciting the different responses to caffeine among individuals. A recent meta-analysis found that caffeine ingestion enhances mean and peak movement velocity in resistance exercise [27]. Nutrients. volume 17, Article number: 21 (2020) The Cyp1a2 contribution was lower than the 87% established using a Cyp1a2 … Beverage caffeine intakes in the U.S. Caffeine content for coffee, tea, soda and more [Internet]. After exercise, in the placebo and caffeine conditions, respectively, 44% and 78% of the participants with the AC/CC genotypes correctly guessed the treatment identity beyond chance, respectively. The caffeine you ingest passes through the stomach and small intestine, entering the bloodstream in a little as 15 minutes. Venier S, Grgic J, Mikulic P. Caffeinated gel ingestion enhances jump performance, muscle strength, and power in trained men. A validated Food Frequency Questionnaire was used to estimate habitual caffeine intake [15]. 2010;42:1375–87. 2016;30:1855–61. Acute effects of caffeine supplementation on movement velocity in resistance exercise: a systematic review and meta-analysis. Research on the effects of caffeine on cardiovascular health found that the effect of caffeine differs between genotypes. First, due to the low number of individuals with the CC genotype, we combined the AC and CC genotypes into one group. Future dose-response studies might consider exploring this hypothesis further. There were no significant differences between the genotype groups for age, body mass, height, 1RM, or habitual caffeine intake. Your caffeine levels peak about 1-hour after consumption and then start to decrease gradually. CYP1A2 genotype and acute effects of caffeine on resistance exercise, jumping, and sprinting performance. Individuals who are ho-mozygous for the CYP1A2*1A allele are “rapid” caffeine metabolizers, whereas car-riers of the variant CYP1A2*1F are “slow” caffeine … The muscle endurance test used in this study further confirmed that caffeine ingestion is ergogenic for this fitness component in resistance-trained men. C or CC are slow caffeine metabolizers %: more than 3 cups of coffee daily. Accessed at https://www.ncbi.nlm.nih.gov/pubmed/24189158, Caffeine content for coffee, tea, soda and more [Internet]. J Strength Cond Res. 2018;15:11. We did not find a significant genotype × caffeine interaction effect (p-values ranged from 0.094 to 0.994) in any of the analyzed performance outcomes. However, a more novel finding is that caffeine is ergogenic for power and velocity outputs when the number of repetitions between the caffeine and placebo conditions is matched. This hypothesis is in line with recent findings that training at a velocity loss of 20% produced greater improvement in CMJ performance than training at a 40% velocity loss [35]. The study involved resistance-trained men as participants. The participants remained seated during the 30-s sprint. In the study by Rahimi [13], the dose was considerably higher (i.e., 6 mg/kg). Furthermore, the results indicated that the habitual heavy caffeine consumers AC individuals had increased basal-DBP when compared to the AA ones. The authors declare that they have no competing interests. After the CMJ test, the participants were provided another 3 minutes of passive rest before starting the Wingate test. The remaining data of the project are published elsewhere [16]. The search for studies was performed through nine databases. Muscle Nerve. All trials were performed in the morning hours (between 7 am and noon), and at the same time of the day across the sessions for each participant, to ensure that the results were not affected by circadian variation [14]. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. Accessed at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3346273/. One-way ANOVA was used to test the differences between genotype groups in age, body mass, height, 1RM, and habitual caffeine intake. A can of Diet Coke has 46 mg of caffeine, while the Monster Energy brand of energy drinks has 160 mg per can. We believe that the pre-exercise responses are of greater importance, given that the improvements during the testing session (or lack thereof) may influence the post-exercise responses. For the analysis, the best jump from three official attempts was used. The cause(s) of this variability are unknown. Before starting the exercise session, in the placebo and caffeine conditions, respectively, 62% and 54% of the participants with the AA genotype correctly guessed the treatment identity beyond chance. One of the early studies [18] conducted on this topic reported that high doses of caffeine (9 mg/kg) are required for acute increases in movement velocity when exercising with very high loads (90% 1RM). Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis. The effectiveness of the blinding was not explored by Rahimi [13] thus limiting the comparison of the results in this aspect of the study design. This is fairly common in this line of research, as the number of individuals with the CC genotype in the population is suggested to be ~ 10% [9]. Samples were collected using buccal swab devices, with OCR-100 kits by DNAGenotek (Ottawa, Canada). This result, therefore, confirms that caffeine ingestion may have a relatively small performance-enhancing effect on vertical jump height [36,37,38]. However, a recent study reported that caffeine ingestion enhances the number of performed repetitions in a resistance exercise session in individuals with the AA genotype but not AC/CC genotypes [13]. 2019. https://doi.org/10.1123/ijspp.2019-0433. Smoking and certain cruciferous vegetables such as broccoli are common triggers that can induce the enzyme, which speed up metabolism, while drugs such as amiodarone (heart medication) and ciprofloxacin (antibiotic)  inhibit it, or slow it down. The first two sessions included familiarization with the exercise protocol. Abstract Purpose Many studies have examined the effect of caffeine on exercise performance, but findings have not always been consistent. The participants had one warm-up jump and three official attempts. Before enrolling in the study, every participant signed an informed consent and filled out a Physical Activity Readiness Questionnaire (PAR-Q). However, the studies included in that meta-analysis assessed either mean or peak velocity; that is, no studies included in the meta-analysis measured both outcomes in the same group of participants [27]. During each repetition, a GymAware linear position transducer (GymAware Power Tool, Kinetic Performance Technologies, Canberra, Australia) was attached to the barbell and used to measure mean concentric velocity (m/s), mean power (W), peak concentric velocity (m/s), and peak power (W). 1. These performance-enhancing effects were observed following the ingestion of using a moderate dose of caffeine (3 mg/kg), which resulted in minimal side effects. Drinking all these different caffeinated drinks can add up and become harder for the body to breakdown, depending on your caffeine metabolism. In case participants respond with “a” or “b”, they were required to state the reason for choosing their response. These individuals would benefit from drinking no more than 2 cups per day to get the full effects from the caffeine. CYP1A2*1F. It is possible that the effects will last more than 5 hours, which could make it harder to fall asleep. Caffeine (1,3,7-trimethylxanthine) is one of the most widely used drugs in the world and is available in many mediums for consumption. According to this notion, AA homozygotes could degrade caffeine into paraxanthine faster than CA and CC individuals [26] which, in turn, could produce a higher clearance of this substance from the Diaz-Lara FJ, Del Coso J, García JM, Portillo LJ, Areces F, Abián-Vicén J. Caffeine improves muscular performance in elite Brazilian Jiu-jitsu athletes. Pickering C, Grgic J. Caffeine and exercise: what next? Placebo effects of caffeine on maximal voluntary concentric force of the knee flexors and extensors. Grgic J, Sabol F, Venier S, Mikulic I, Bratkovic N, Schoenfeld BJ, Pickering C, Bishop DJ, Pedisic Z, Mikulic P. What dose of caffeine to use: acute effects of 3 doses of caffeine on muscle endurance and strength. J Strength Cond Res. Int J Sports Physiol Perform. Effects of velocity loss during resistance training on athletic performance, strength gains and muscle adaptations. After the final repetition with 90% of 1RM, participants were provided with 5 min of passive rest. Biotransformation of caffeine, paraxanthine, theobromine and theophylline by cDNA-expressed human CYP1A2 and CYP2E1. The comparisons of the effects of caffeine on exercise performance between individuals with the AA genotype and AC/CC genotypes found no significant differences. That they have no competing interests can improve cognition, as well as mental alertness to! Characteristics are presented in Table 1, a genetic testing company alertness and enhance physical performance ”! 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