Ergogenic Effects Of Caffeine Research Articles

Caffeine Boosts Weight-Lifting Performance in Rats: A Pilot Study.

Caffeine is a well-described ergogenic aid used to enhance athletic performance. Using animal models can greatly increase our understanding of caffeine's mechanisms in performance. Here, we adapted an animal weight-lifting exercise model to demonstrate caffeine's ergogenic effect in rats. Male Wistar rats (315 ± 35 g) were randomly divided into two groups: one group received 5 mg·kg-1 of caffeine (0.5 mL; CEx; n = 5) and the other 0.9% NaCl (0.5 mL; PEx; n = 4) through an orogastric probe (gavage) one hour before exercise. Weight-lifting exercise sessions were performed over three subsequent days, and the number of complete squats performed was counted. Analyses of the area under the curve in all three experiments showed that the CEx group responded more to stimuli, performing more squats (1.7-, 2.0-, and 1.6-fold; p < 0.05) than the control group did. These three days' data were analyzed to better understand the cumulative effect of this exercise, and a hyperbolic curve was fitted to these data. Data fitting from the caffeine-supplemented group, CEx, also showed larger Smax and Kd (2.3-fold and 1.6-fold, respectively) than the PEx group did. Our study demonstrated an acute ergogenic effect of caffeine in an animal weight-lifting exercise model for the first time, suggesting potential avenues for future research.

Ergogenic effects of the combination of caffeine and New Zealand blackcurrant supplements on time trial

The use of single supplements to enhance performance is widespread among athletes. The aim of this study was to increase knowledge about the combined effects of caffeine and New Zealand blackcurrant (NZBC) dietary supplements. In this counterbalanced alternating treatment single-case design, two participants each underwent four phases of four sessions in a double-blind, randomized order. After a 3-week pre-test phase, the supplement combinations of placebo/placebo, caffeine/placebo (5 mg/kg), NZBC/placebo (600 mg), and caffeine/NZBC (5 mg/kg + 600 mg) were taken and weekly performance tests were conducted to examine their effects on relative power (W/kg) during a 20-minute time trial on a bicycle. Data were analyzed descriptively and using the Tau-U calculator from Single Case Research. The ergogenic effect of caffeine was confirmed in both participants, with increases of 3.3% and 6.5%, while the positive effect of NZBC on performance was only seen in one participant (13.4%). The combination of caffeine and NZBC again increased performance in both participants (2.2% and 19.2%), but the data only showed a near additive effect of the supplements in one participant. The participants did not show a consistent performance improvement with the combined intake of the supplements caffeine and NZBC. Further studies are required to confirm or refute this evidence of the synergistic effects of these supplements.

Ergogenic effects of caffeine are mediated by myokines.

Exercise has long been known to effectively improve and enhance skeletal muscle function and performance. The favorable effects of exercise on remote organs other than skeletal muscle are well known, but the underlying mechanism has remained elusive. Recent studies have indicated that skeletal muscle not only enables body movement, but also contributes to body homeostasis and the systemic stress response via the expression and/or secretion of cytokines (so-called myokines). Not only the induction of muscle contraction itself, but also changes in intracellular calcium concentration ([Ca2+]i) have been suggested to be involved in myokine production and secretion. Caffeine is widely known as a Ca2+ ionophore, which improves skeletal muscle function and exercise performance (i.e., an "ergogenic aid"). Interestingly, some studies reported that caffeine or an increase in [Ca2+]i enhances the expression and/or secretion of myokines. In this review, we discuss the association between caffeine as an ergogenic aid and myokine regulation.

Caffeine consumption within British fencing athletes.

The ergogenic effects of caffeine are well documented, yet despite the potential benefits of supplementation, there is a lack of understanding of caffeine habits and supplementation within fencing. British fencers (n = 136) completed a Web-based questionnaire, exploring self-reported caffeine consumption, reasons for use and education. Fencers (94.1%) habitually consumed caffeine, primarily due to the taste of the products (93.8%). Respondents ingested 183.4 ± 137.5 mg of caffeine daily, with a significant difference between age groups (p < 0.05). Many respondents (30.1%) consumed caffeine 60 mins prior/during fencing training and/or competition with the main reason highlighted as cognitive performance enhancement. Respondents ingested 140.8 ± 104.6 mg of caffeine during training/competition, mainly as energy drinks, bars, and powders. Education on caffeine supplementation was low (25.7%), with significant associations between age groups (p < 0.05). Evidence implies caffeine toxicity has been experienced by 35% of fencers, highlighting the need for education on caffeine consumption. To conclude there is evidence of caffeine supplementation in fencing, primarily to magnify cognitive performance. However, there is a requirement for targeted education on caffeine supplementation to fencers, so that negative side effects and potential anti-doping infringements can be avoided.

Influence of caffeine on the maximal isometric and concentric force produced by skinned fibers

Caffeine is one of the most famous and widely used ergogenic drugs, especially by athletes to improve sports performance. Caffeine is known to enhance muscle contraction by facilitating Ca2+ release from the sarcoplasmic reticulum. While the effect of caffeine on the cross-bridge dynamics has also investigated, the results is controversial. Therefore, the purpose of this study was to examine the influence of caffeine on cross-bridge dynamics using skinned fiber preparations from rabbit soleus (N = 19 in total). We performed isometric contractions at an average sarcomere length of 2.4 μm; thereafter, skinned fibers were shortened by 20% of the fiber length at a velocity of 0.1 mm/s (slow shortening) or 0.5 mm/s (fast shortening). The contractions were performed under both normal and caffeine-containing activating solution conditions to compare the isometric, slow concentric, and fast concentric forces between conditions. The isometric force did not differ between normal and caffeine-containing activating solution conditions. Similarly, the concentric forces obtained during the slow and fast shortening trials did not differ between conditions. We also measured the stiffness and the rate of force redevelopment (kTR) during the isometric contraction phase and found that these values were not different between normal and caffeine conditions. Based on these results, we conclude that the influence of caffeine on cross-bridge dynamics is negligible, and the ergogenic effect of caffeine, from the view of muscle contractility, is by facilitating Ca2+ release, as suggested in previous studies, and not by modulating the cross-bridge dynamics.

Effects of caffeine on isometric handgrip strength: A meta-analysis.

Several studies explored the effects of caffeine on isometric handgrip strength, but their findings varied. Therefore, the aim of this review was to perform a meta-analysis of studies exploring the effects of caffeine on isometric handgrip strength. Search for studies was performed through five databases (Academic Search Elite, Cochrane Library, PubMed/MEDLINE, SPORTDiscus, and Scopus) with additional secondary searches. RoB 2 scale was used to evaluate the risk of bias of the included studies. The effects of caffeine vs. placebo were analyzed in a random-effects meta-analysis. Sixteen studies were included (n=353; n=34 females). The studies were classified as having "some concerns" (possible bias from the randomization process and in the measurement of the outcome) on the RoB 2 scale. In the main meta-analysis, caffeine ingestion enhanced isometric handgrip strength (d: 0.17; 95% confidence interval [CI]: 0.10, 0.23; p<0.001). In subgroup analyses, an ergogenic effect of caffeine on isometric handgrip strength was found when consumed in small doses (1-3mg/kg; d: 0.20; 95% CI: 0.10, 0.30; p<0.001), moderate-to-high doses (5-7mg/kg; d: 0.15; 95% CI: 0.07, 0.23; p<0.001), liquid form (d: 0.19; 95% CI: 0.09, 0.30; p<0.001), and capsule form (d: 0.15; 95% CI: 0.06, 0.23; p<0.001). Overall, individuals interested in the acute enhancement of isometric handgrip strength may consider caffeine supplementation in small or moderate-to-high doses. However, these ergogenic effects were very small and were observed mostly among male participants.

The role of caffeine consumption on individuals' health and athletic performance: An overview

Caffeine is considered a very popular, extensively ingested substance among the general population and athletes or recreational exercisers. This narrative review seeks to present the most recent scientific literature on the role of caffeine consumption on individuals' health and athletic performance. There are favorable relations between coffee use and liver outcomes (e.g. cirrhosis, fibrosis, liver cancer, and chronic liver disease), and a wide range of other health outcomes, while, there are no decisive deleterious relations with any health outcomes, except for pregnancy. The ergogenic effects of caffeine are significant after consumption of doses 3 to 6 mg/kg/body weight, 15 to 60 min pre-exercise (it depends on the form), mainly due to the Central Nervous System. Caffeine may enhance the re-synthesis of glycogen during the recovery phase from exercise. Caffeine has beneficial effects in several features of exercise such as extended aerobic-type activities, fixed-term activities, brief duration activities, high-intensity prolonged exercise as in team sports, and strength/power activities. It does not cause harmful changes in urination, water loss, sweating rate, and fluid balance. In periods of sleep deprivation, it can improve vigilance and alertness. Among the most commonly incorporated side effects of caffeine, ingestion is anxiety and heart palpitations.

Effects of Caffeine on Resistance Exercise: A Review of Recent Research.

In the last few years, a plethora of studies have explored the effects of caffeine on resistance exercise, demonstrating that this field of research is growing fast. This review evaluates and summarizes the most recent findings. Given that toxic doses of caffeine are needed to increase skeletal muscle contractility, the binding of caffeine to adenosine receptors is likely the primary mechanism for caffeine's ergogenic effects on resistance exercise. There is convincing evidence that caffeine ingestion is ergogenic for (i) one-repetition maximum, isometric, and isokinetic strength; and (ii) muscular endurance, velocity, and power in different resistance exercises, loads, and set protocols. Furthermore, there is some evidence that caffeine supplementation also may enhance adaptations to resistance training, such as gains in strength and power. Caffeine ingestion is ergogenic for resistance exercise performance in females, and the magnitude of these effects seems to be similar to that observed in men. Habitual caffeine intake and polymorphisms within CYP1A2 and ADORA2A do not seem to modulate caffeine's ergogenic effects on resistance exercise. Consuming lower doses of caffeine (e.g., 2-3mg/kg) appears to be comparably ergogenic to consuming high doses of caffeine (e.g., 6mg/kg). Minimal effective doses of caffeine seem to be around 1.5mg/kg. Alternate caffeine sources such as caffeinated chewing gum, gel, and coffee are also ergogenic for resistance exercise performance. With caffeine capsules, the optimal timing of ingestion seems to be 30-60min before exercise. Caffeinated chewing gums and gels may enhance resistance exercise performance even when consumed 10min before exercise. It appears that caffeine improves performance in resistance exercise primarily due to its physiological effects. Nevertheless, a small portion of the ergogenic effect of caffeine seems to be placebo-driven.

Short-term effects of caffeine intake on binocular accommodative facility: a quantitative and qualitative analysis

ABSTRACT Clinical relevance Caffeine intake has been demonstrated to influence several physiological measures, including some related to eye physiology. The ability to focus at different distances is of paramount importance in real-world situations, and thus, the possible impact of caffeine intake on accommodative facility may have important clinical implications. Background This placebo-controlled, double-blind, balanced crossover study aimed to assess the acute effects of caffeine ingestion on the frequency and precision of the binocular accommodative facility. Methods Twenty university students (21.9 ± 3.4 years) ingested a capsule of caffeine (4 mg/kg) or placebo (300 mg of corn-starch) on two different days and counterbalanced order. The binocular accommodative facility was objectively assessed, using the WAM-5500 binocular open-field autorefractometer, after 60 min of capsule ingestion (caffeine/placebo). Perceived levels of activation was also assessed in each experimental condition. Results The ingestion of a single administration of caffeine (~ 4 mg/kg) causes an increase in the number of cycles performed per minute (p = 0.023, Cohen’s d = 0.55), whereas no effects were observed for the mean magnitude of accommodative change between the far and near targets (p = 0.794), and the percentage of incorrect cycles of accommodation and dis-accommodation (p = 0.271 and 0.396, respectively). Participants reported a perceived level of activation of 6.8 ± 1.5 and 7.6 ± 1.8 in the placebo and caffeine conditions, respectively (p = 0.059). Conclusion Caffeine intake improves quantitative, but not qualitative, measures of accommodative facility. These results corroborate the impact of caffeine on visual function and suggest that this ergogenic effect of caffeine may be used to enhance visual performance in applied situations.

Belief in caffeine's ergogenic effect on cognitive function and endurance performance: A sham dose-response study.

This study aimed to determine if belief in caffeine's ergogenic potential influences choice reaction time (CRT) and/or running performance. Twenty-nine healthy individuals (23.7±5 years, 16 males) completed two trials (one week apart). Before the trials, participants indicated their "belief" in caffeine's ergogenic effects and previous "experience" using caffeine for performance. On arrival, participants randomly received either sham "Low (100mg; LD)" or "High (300mg; HD)" dose caffeine capsules 30-min before commencing the CRT test, followed by a 10km run. Paired samples t-tests determined differences between trials for CRT latency (Ex-Gaussian analysis; μ-, σ- and τ-) and running performance using the entire cohort and sub-groups exhibiting strong "beliefs"+/-"experience". Sham caffeine dose did not influence CRT (μ-, σ- and τ-respectively, LD: 400±53ms vs. HD: 388±41ms; LD: 35±18ms vs. HD: 34±17ms; LD: 50±24ms vs. HD: 52±19ms, all p's>0.05). Neither belief (n=6), nor belief+experience (n=4), influenced this effect. Furthermore, caffeine dose did not influence run time (LD: 49.05±3.75min vs. HD: 49.06±3.85min, p=0.979). Belief (n=9) (LD: 48.93±3.71min vs. HD: 48.9±3.52min, p=0.976), and belief+experience (n=6) (LD: 48.68±1.87min vs. HD: 49.55±1.75min, p=0.386) didn't influence this effect. A dose-response to sham caffeine ingestion was not evident on cognitive or endurance performance in healthy individuals, regardless of their convictions about caffeine's ergogenicity.

Acute caffeine supplementation improves jumping, sprinting, and change-of-direction performance in basketball players when ingested in the morning but not evening

ABSTRACT This study compared the effects of acute caffeine supplementation (3 mg/kg) administered in the morning and evening on performance-related variables in basketball players. Eleven, national-level, adolescent male basketball players underwent field-based fitness testing on four occasions: morning (10:00) with caffeine ingestion (AMCAFF), morning (10:00) with placebo ingestion (AMPLAC), evening (21:00) with caffeine ingestion (PMCAFF), and evening (21:00) with placebo ingestion (PMPLAC). Fitness testing included of a countermovement jump without arm swing (CMJ), CMJ with arm swing (CMJAS), squat jump (SJ), Lane Agility Drill (LAD), 20-m linear sprint, and Suicide Run with (SRD) and without dribbling (SR). Data were analysed using two-way repeated measures analyses of variance and paired t-tests, with effect sizes (ES) also determined for all pairwise comparisons. Follow-up t-test comparisons revealed that AMCAFF produced small-moderate, significant (p<0.001), improvements in CMJ (ES = 0.51), CMJAS (ES = 0.40), SJ (ES = 0.51), and SR (ES = −0.45) compared to AMPLAC. AMCAFF also produced a moderate, significantly (p<0.001) faster LAD (ES = −0.61) compared to PMCAFF. PMPLAC demonstrated small-moderate, significant (p<0.05) improvements in CMJ (ES = 0.43), CMJAS (ES = 0.48), and 20-m sprint (ES = −0.63) compared to AMPLAC. In contrast, AMPLAC resulted in large, significantly (p<0.001), faster SRD (ES = −1.46) and SR (ES = −1.59) compared to PMPLAC. Given the ergogenic effects of caffeine during basketball-specific fitness tests appear to be influenced by time of ingestion, basketball practitioners should consider administering caffeine only to players in the morning to improve vertical jump, sprinting, and change-of-direction performance, with no beneficial effects observed with caffeine ingestion in the evening. Highlights The effect of caffeine supplementation on basketball-specific performance related variables were mediated by ingestion time in elite, adolescent basketball players. AMCAFF produced small-moderate improvements in vertical jump, change-of-direction, 20-m linear sprint, and repeated-sprint performance compared to AMPLAC while PMCAFF produced trivial differences in each performance-related variable compared to PMPLAC. Comparisons between ingestion times in the placebo condition revealed vertical jump height and 20-m sprint speed were impaired in the morning compared to the evening, but these time-dependent differences were eliminated when caffeine was consumed in the morning. Basketball practitioners should consider administering caffeine only to players in the morning to improve vertical jump, sprinting, and change-of-direction performance, with no beneficial effects observed with caffeine ingestion in the evening.

Novel insights on caffeine supplementation, CYP1A2 genotype, physiological responses and exercise performance.

Caffeine is a popular ergogenic aid due to its primary physiological effects that occur through antagonism of adenosine receptors in the central nervous system. This leads to a cascade of physiological reactions which increases focus and volition, and reduces perception of effort and pain, contributing to improved exercise performance. Substantial variability in the physiological and performance response to acute caffeine consumption is apparent, and a growing number of studies are implicating a single-nucleotide polymorphism in the CYP1A2 gene, responsible for caffeine metabolism, as a key factor that influences the acute responses to caffeine ingestion. However, existing literature regarding the influence of this polymorphism on the ergogenic effects of caffeine is controversial. Fast caffeine metabolisers (AA homozygotes) appear most likely to benefit from caffeine supplementation, although over half of studies showed no differences in the responses to caffeine between CYP1A2 genotypes, while others even showed either a possible advantage or disadvantage for C-allele carriers. Contrasting data are limited by weak study designs and small samples sizes, which did not allow separation of C-allele carriers into their sub-groups (AC and CC), and insufficient mechanistic evidence to elucidate findings. Mixed results prevent practical recommendations based upon genotype while genetic testing for CYP1A2 is also currently unwarranted. More mechanistic and applied research is required to elucidate how the CYP1A2 polymorphism might alter caffeine's ergogenic effect and the magnitude thereof, and whether CYP1A2 genotyping prior to caffeine supplementation is necessary.

Caffeine, exercise physiology, and time-trial performance: no effect of ADORA2A or CYP1A2 genotypes.

The aim of this study was to investigate the influence of ADORA2A and CYP1A2 genotypes on the physiological and ergogenic effects of caffeine. Sixty-six male cyclists were screened for ADORA2A and CYP1A2 genotypes; with 40 taking part subsequently in a randomised, double-blind, placebo-controlled study. Trial 1 was used to establish the oxygen uptake-power output relationship and maximal oxygen uptake. In trials 2 and 3, participants ingested 5 mg·kg-1 of caffeine or placebo 1 h before completing a submaximal incremental cycling test, followed by a time-trial (∼30 min). Relative to placebo, caffeine led to a significant reduction in time to complete the time-trial (caffeine: 29.7 ± 1.8 min; placebo: 30.8 ± 2.3 min); but there was no effect of genotype. During submaximal exercise, caffeine reduced mean heart rate by 2.9 ± 3.7 beats·min-1, with effects dissipating as exercise intensity increased. Caffeine also significantly reduced perceived exertion by 0.5 ± 0.8, and increased blood lactate by 0.29 ± 0.42 mmol·L-1, respiratory exchange ratio by 0.013 ± 0.032, and minute ventilation by 3.1 ± 6.8 L·min-1. Nonetheless, there were no supplement × genotype interactions. In conclusion, caffeine influences physiological responses to submaximal exercise and improves time-trial performance irrespective of ADORA2A or CYP1A2 genotypes. Novelty: Caffeine affects physiological responses at rest and during submaximal exercise independent of ADORA2A or CYP1A2 genotypes. Variability in the effect of caffeine on time-trial performance is not explained by ADORA2A or CYP1A2 genotypes.

Caffeine increases whole-body fat oxidation during 1h of cycling at Fatmax.

The ergogenic effect of caffeine on exercise of maximum intensity has been well established. However, there is controversy regarding the effect of caffeine on shifting substrate oxidation at submaximal exercise. The aim of this study was to investigate the effect of acute caffeine ingestion on whole-body substrate oxidation during 1h of cycling at the intensity that elicits maximal fat oxidation (Fatmax). In a double-blind, randomized, and counterbalanced experiment, 12 healthy participants (VO2max = 50.7 ± 12.1mL/kg/min) performed two acute experimental trials after ingesting either caffeine (3mg/kg) or a placebo (cellulose). The trials consisted of 1h of continuous cycling at Fatmax. Energy expenditure, fat oxidation rate, and carbohydrate oxidation rate were continuously measured by indirect calorimetry. In comparison to the placebo, caffeine increased the amount of fat oxidized during the trial (19.4 ± 7.7 vs 24.7 ± 9.6g, respectively; P = 0.04) and decreased the amount of carbohydrate oxidized (94.6 ± 30.9 vs 73.8 ± 32.4g; P = 0.01) and the mean self-perception of fatigue (Borg scale = 11 ± 2 vs 10 ± 2 arbitrary units; P = 0.05). In contrast, caffeine did not modify total energy expenditure (placebo = 543 ± 175; caffeine = 559 ± 170kcal; P = 0.60) or mean heart rate (125 ± 13 and 127 ± 9 beats/min; P = 0.30) during exercise. Before exercise, caffeine increased systolic and diastolic blood pressure whilst it increased the feelings of nervousness and vigour after exercise (P < 0.05). These results suggest that a moderate dose of caffeine (3mg/kg) increases the amount of fat oxidized during 1h of cycling at Fatmax. Thus, caffeine might be used as an effective strategy to enhance body fat utilization during submaximal exercise. The occurrence of several side effects should be taken into account when using caffeine to reduce body fat in populations with hypertension or high sensitivity to caffeine.

Effects of CYP1A2 and ADORA2A Genotypes on the Ergogenic Response to Caffeine in Professional Handball Players.

Previous investigations have found that several genes may be associated with the interindividual variability to the ergogenic response to caffeine. The aim of this study is to analyze the influence of the genetic variations in CYP1A2 (−163C > A, rs762551; characterized such as “fast” (AA genotype) and “slow” caffeine metabolizers (C-carriers)) and ADORA2A (1976T > C; rs5751876; characterized by “high” (TT genotype) or “low” sensitivity to caffeine (C-carriers)) on the ergogenic response to acute caffeine intake in professional handball players. Thirty-one professional handball players (sixteen men and fifteen women; daily caffeine intake = 60 ± 25 mg·d−1) ingested 3 mg·kg−1·body mass (bm) of caffeine or placebo 60 min before undergoing a battery of performance tests consisting of a countermovement jump (CMJ), a sprint test, an agility test, an isometric handgrip test, and several ball throws. Afterwards, the handball players performed a simulated handball match (2 × 20 min) while movements were recorded using inertial units. Saliva samples were analyzed to determine the genotype of each player for the −163C > A polymorphism in the CYP1A2 gene (rs762551) and for the 1976T > C polymorphism in the ADORA2A gene (rs5751876). In the CYP1A2, C-allele carriers (54.8%) were compared to AA homozygotes (45.2%). In the ADORA2A, C-allele carriers (80.6%) were compared to TT homozygotes (19.4%). There was only a genotype x treatment interaction for the ball throwing from 7 m (p = 0.037) indicating that the ergogenic effect of caffeine on this test was higher in CYP1A2 AA homozygotes than in C-allele carriers. In the remaining variables, there were no genotype x treatment interactions for CYP1A2 or for ADORA2A. As a whole group, caffeine increased CMJ height, performance in the sprint velocity test, and ball throwing velocity from 9 m (2.8–4.3%, p = 0.001–0.022, effect size = 0.17–0.31). Thus, pre-exercise caffeine supplementation at a dose of 3 mg·kg−1·bm can be considered as an ergogenic strategy to enhance some neuromuscular aspects of handball performance in professional handball players with low daily caffeine consumption. However, the ergogenic response to acute caffeine intake was not modulated by CYP1A2 or ADORA2A genotypes.

Neuronal adenosine A2A receptors signal ergogenic effects of caffeine

Caffeine is one of the most used ergogenic aid for physical exercise and sports. However, its mechanism of action is still controversial. The adenosinergic hypothesis is promising due to the pharmacology of caffeine, a nonselective antagonist of adenosine A1 and A2A receptors. We now investigated A2AR as a possible ergogenic mechanism through pharmacological and genetic inactivation. Forty-two adult females (20.0 ± 0.2 g) and 40 male mice (23.9 ± 0.4 g) from a global and forebrain A2AR knockout (KO) colony ran an incremental exercise test with indirect calorimetry (V̇O2 and RER). We administered caffeine (15 mg/kg, i.p., nonselective) and SCH 58261 (1 mg/kg, i.p., selective A2AR antagonist) 15 min before the open field and exercise tests. We also evaluated the estrous cycle and infrared temperature immediately at the end of the exercise test. Caffeine and SCH 58621 were psychostimulant. Moreover, Caffeine and SCH 58621 were ergogenic, that is, they increased V̇O2max, running power, and critical power, showing that A2AR antagonism is ergogenic. Furthermore, the ergogenic effects of caffeine were abrogated in global and forebrain A2AR KO mice, showing that the antagonism of A2AR in forebrain neurons is responsible for the ergogenic action of caffeine. Furthermore, caffeine modified the exercising metabolism in an A2AR-dependent manner, and A2AR was paramount for exercise thermoregulation.

Caffeine improves various aspects of athletic performance in adolescents independent of their 163 C>A CYP1A2 genotypes.

The purpose of this study was to investigate whether variations in 163 C>A CYP1A2 genotypes (rs 762551) (AA, AC, and CC) modify the ergogenic effects of caffeine (CAF) on strength, power, muscular endurance, agility, and endurance in adolescent athletes. One hundred adolescents (age=15±2years) were recruited. Participants ingested CAF (6mg.kg-1 ) or placebo (PLA, 300mg of cellulose) 1hour before performing a sequence of physical tests: handgrip strength, vertical jumps, agility test, sit-ups, push-ups, and the Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1). Compared to PLA, CAF enhanced (P<.05) sit-up (CAF=37±9; PLA=35±8 repetitions) and push-up repetitions (CAF=26±11; PLA=24±11 repetitions), and increased distance covered in Yo-Yo IR1 test (CAF=1010.4±378.9; PLA=903.2±325.7m). There was no influence of CAF on handgrip strength (CAF=35.1±8.9; PLA=33.7±8.7 kgf), countermovement jump height (CAF=49.3±12.6; PLA=47.9±13.8cm), spike jump height (CAF=54.2±13.6; PLA=52.9±14.5cm), and time in agility test (CAF=15.8±1.1; PLA=15.9±1.3s, P>.05). When present, the ergogenic effect of CAF was not dependent of genotype. CAF improves muscular endurance and aerobic performance in adolescent athletes, regardless of their 163 C>A CYP1A2 genotype.

Abstracts From the December 2019 International Sport + Exercise Nutrition Conference in Newscastle upon Tyne

It is well established that caffeine supplementation can enhance endurance exercise performance. However, inter-individual variability in the ergogenic effect of caffeine has been reported. This variability has not been adequately explained, but could reflect differences in habitual caffeine intake, training status, or age. Common genetic polymorphisms in genes encoding proteins involved in the metabolism and physiological actions of caffeine may also be important. A functional single nucleotide polymorphism (SNP) in the adenosine A2a receptor gene (ADORA2a; 1976 T>C; rs5751876) has been reported to influence the ergogenic response to caffeine. In women undertaking a 10 min time-trial, caffeine ingestion improved performance in all women with a T/T genotype (n=6), whereas in those carrying a C allele, performance only improved in one of six participants. Only 10 to 20% of the population have a T/T genotype, so a lack of effect of caffeine in those with a C allele seems improbable. Thus, the aim of the current study was to further explore the effect of the ADORA2a 1976 T>C SNP on the ergogenic effect of caffeine. Trained cyclists (n=23; age 38 (SD 11) y, mass 71.7 (SD 12.3) kg, BMI 22.9 (SD 2.3) kg/m2, VO2 max 60.7 (SD 10.8) ml/kg/min) completed a randomised cross-over trial. Each participant completed a VO2max test, and 3 x 16 km time trials (1 x familiarisation and 2 x experimental trials) on a cycle ergometer. Caffeine (3 mg/kg) or placebo was consumed 60 min before the experimental time trials. The effect of caffeine on performance and interaction with genotype was assessed with a mixed model ANOVA. Caffeine caused a 1% decrease in time trial time (-15.1 s, 95% CI, -24.9, -5.3; p=0.016). There was no significant interaction between ADORA2a genotype and change in 16 km time when participants were split into 3 genotypes (TT (n=5), CT (n=4) and CC (n=14); p=0.928) or grouped based on the presence of a C or T allele (TT v CT/CC combined; p=0.715; CC v CT/TT combined; p=0.896). Moreover, the magnitude of the decrease in time was similar for each genotype (CC = 15.6 s; CT = 17.5 s, TT = 11.7 s). In the present study there was no indication that a common functional SNP in the ADORA2a gene modifies the ergogenic effect of a moderate dose of caffeine on 16 km cycling time-trial performance in trained male cyclists.

Inconsistency in the Ergogenic Effect of Caffeine in Athletes Who Regularly Consume Caffeine: Is It Due to the Disparity in the Criteria That Defines Habitual Caffeine Intake?

Caffeine is the most popular psychoactive substance in the world, and data suggests that it is widely used by athletes before competition to enhance physical and mental performance. The high number of athletes that regularly use caffeine suggests the need to investigate the effect of acute caffeine ingestion in athletes habituated to caffeine. However, most of the studies supporting this claim have used samples of athletes who do not consume caffeine on a regular basis, and with caffeine intake withdrawal prior to the experiments. A search through 19 databases conducted on habitual caffeine users was performed. The results of the studies regarding the ergogenic effect of caffeine in naïve vs. habitual caffeine consumers are contradictory. The diversity of results are likely associated with the use of different thresholds to categorize individuals as naïve or high caffeine consumers. There are no valid and standardized methods to accurately estimate the amount of caffeine ingested per day in athletes. We proposed a classification of athletes that habitually consume caffeine by using dietary questionnaires, and ultimately, to reduce the likelihood of discrepancies caused by the improper qualification of daily caffeine intake in studies directed at the assessment of acute caffeine intake in habitual caffeine consumers.

Addition of Caffeine to a Carbohydrate Feeding Strategy Prior to Intermittent Exercise.

The ergogenic effect of caffeine is well established, although no investigations providing a high carbohydrate feeding strategy (pre-exercise meal=2 g/kg BM) co-ingested with caffeine exist for soccer. This investigation examines the effect of caffeine in addition to a pre-exercise carbohydrate meal and drink mid-way through a soccer simulation. Eight recreational soccer players completed an 85-minute soccer simulation followed by an exercise capacity test (Yo-yo Intermittent Endurance test level 2) on two occasions. Prior to exercise participants consumed a high carbohydrate meal, with placebo or 5 mg/kg BM-1 caffeine. No significant performance effect was identified (p=0.099) despite a 12.8% (109 m) improvement in exercise capacity following caffeine. Rates of carbohydrate and fat oxidation did not differ between conditions and nor were differences apparent for plasma glucose, fatty acids, glycerol, β-hydroxybutyrate (p>0.05). However, an increase in lactate was observed for caffeine (p=0.039). A significant condition effect on rating of perceived exertion was identified (p<0.001), with the overall mean for the protocol lowered to 11.7±0.9 au for caffeine compared to 12.8±1.3 au. Caffeine supplementation with a carbohydrate feeding strategy failed to affect metabolic and metabolite responses, although reductions in perception of exercise were observed. While a 12.8% increase in exercise capacity was noted the findings were not significant, possibly due to the small sample size.