The Influence of Caffeine Expectancies on Sport, Exercise, and Cognitive Performance

Caffeine Mouth Rinse Plus Ingestion Improves the 10-Km Time Trial Compared to Caffeine Mouth Rinse Alone

Background: The benefits of caffeine to physical performance have been extensively demonstrated, however, it has recently been speculated that there is an effect of the administration route on its effectiveness. Purpose: The current study investigated the effect of caffeine mouth rinse in isolation or combined with ingestion on performance in a 30-minute constant-load exercise followed by a 10-km cycling time trial. Methods: Ten physically active men performed a 30-minute constant-load exercise at 50% of the graded test Wmax, followed by a 10-km cycling time trial. Before and at the middle points of the constant-load exercise and 10-km cycling time trial, the following conditions were administered: PLA (cellulose ingestion plus mouth rinsing with magnesium sulfate), ING (5 mg.kg-1 of caffeine ingestion plus mouth rinsing with magnesium sulfate), MR (cellulose ingestion plus mouth rinsing with 1.2% caffeine), and COMB (5 mg.kg-1 of caffeine ingestion plus mouth rinsing with 1.2% caffeine). Results: During the 30-minute constant-load exercise, COMB presented a lower rating of perceived exertion (RPE) than MR (p = .04). For the 10-km time trial, the COMB was faster than MR (MR = 1363 ± 345 vs. COMB = 1291 ± 308s, Δ% = 5.57, p = .05). Mean power output was higher in COMB than PLA, ING, and MR (234 ± 15 vs. 169 ± 29, 148 ± 11, and 145 ± 12 W, respectively). There were no differences between conditions for heart rate and RPE during the 10-km time trial. Conclusion: In summary, caffeine mouth rinsing potentiated the effects of caffeine ingestion during the 10-km time trial compared to caffeine mouth rinsing alone.

Boosting physical performance in SD rats through brain-targeted delivery of caffeine-loaded transferrin liposomes

This study aimed to explore the impact of caffeine (CAF) encapsulated in transferrin-modified, sterically-stabilized liposomes (Tf-SSL) on the physical performance of rats, specifically forelimb grip strength, running, and swimming. The brain-targeted drug delivery system, Tf-SSL, was used for the administration of caffeine. 168 male Sprague-Dawley (SD) rats were randomly assigned to different groups, including swimming, running, running wheel, and strength groups. Each group was further subdivided into high, medium, and low dose free caffeine (HCAF, MCAF, LCAF) and Tf-SSL CAF groups, along with a control group (CON). The strength, swimming, and running groups underwent training for four weeks, three times per week. The running wheel group was placed in rearing cages for a one-week adaptation period. After the final training session, the resistance, swimming, running, and running wheel exercise capacities of the rats were tested. The rats were administered treatment via tail vein injection, while the blank CON group received 0.9 % saline solution without treatment throughout the entire process. The results demonstrated a Tf-SSL CAF group encapsulation rate of 70.58 ± 5.14 %. Increasing the concentration of supplemented caffeine led to enhanced forelimb grip strength in rats, with significant differences observed in HCAF alone group, medium-dose Tf-SSL CAF (MTf-SSL CAF), and high-dose Tf-SSL CAF (HTf-SSL CAF) groups compared to the CON group. In the running and swimming experiments, higher caffeine supplementation concentrations correlated with increased running and swimming time to exhaustion, and the MTf-SSL CAF group showed longer running and swimming time compared to the HCAF alone group. The results of rat striatal dopamine levels indicated that increased caffeine supplementation concentrations led to higher dopamine secretion, with significantly different striatal concentrations in the HCAF group, MTf-SSL CAF group, and HTf-SSL CAF group compared to the CON group. The running wheel experiment revealed that rats in the medium- and high-dose Tf-SSL CAF groups exhibited greater 6-h running distances than the HCAF group and CON group. In conclusion, caffeine supplementation improved the physical performance of rats, with the high concentration CAF group outperforming the low and medium concentration groups. Furthermore, Tf-SSL CAF demonstrated superior physical enhancement compared to caffeine supplementation alone.

Caffeine improves the shooting performance and reaction time of first-person shooter esports players: a dose-response study

Caffeine is recognized as one of the most effective dietary ergogenic aids in sports, yet its evidence-based effectiveness in esports is unclear. This study investigated the effects of two different doses of caffeine on the shooting performance and reaction time of 24 first-person shooter (FPS) esports players (22 men, 2 women; age = 22.29 ± 2.91 years). Participants completed three experimental trials in which they consumed either a water control (CON), a 1 mg·kg-1 BM (CAF1) or a 3 mg·kg-1 BM (CAF3) dose of caffeine. Performance measures (e.g., score, accuracy (%), hit rate (hits/sec), and shots fired) were assessed in a static clicking and reactive tracking style task on the KovaaK's FPS aim trainer. Reaction time was used to assess vigilance on the psychomotor vigilance test (PVT). Performance was measured at four time points in each trial: pre-treatment (PRE), 60 min (POST1), 80 min (POST2), and 100 min (POST3) post-treatment. Significant differences were identified using repeated-measures analysis of variances. Caffeine, irrespective of dose, significantly improved performance compared to CON for static clicking score and hit rate, reactive tracking accuracy, and reaction time on the PVT. Significant interactions between treatment and time were identified and post hoc analyses showed that compared to CON, CAF1 significantly improved static clicking score at POST1 and POST3, static clicking hit rate at POST1, reactive tracking accuracy at POST1, POST2, and POST3, and reaction time on the PVT at POST1 and POST2. Post hoc analysis also showed that compared to CON, CAF3 significantly improved static clicking score, reactive tracking accuracy, and reaction time on the PVT at all time points, in addition to static clicking hit rate at POST1 and POST3. In summary, caffeine supplementation enhances the shooting performance and reaction time of FPS esports players.

Caffeine, but Not Creatine, Improves Anaerobic Power Without Altering Anaerobic Capacity in Healthy Men During a Wingate Anaerobic Test

There is a lack of evidence on the additional benefits of combining caffeine (CAF) and creatine (CRE) supplementation on anaerobic power and capacity. Thus, the aim of the present study was to test the effects of combined and isolated supplementation of CAF and CRE on anaerobic power and capacity. Twenty-four healthy men performed a baseline Wingate anaerobic test and were then allocated into a CRE (n = 12) or placebo (PLA; n = 12) group. The CRE group ingested 20 g/day of CRE for 8 days, while the PLA group ingested 20 g/day of maltodextrin for the same period. On the sixth and eighth days of the loading period, both groups performed a Wingate anaerobic test 1 hr after either CAF (5 mg/kg of body mass; CRE + CAF and PLA + CAF conditions) or PLA (5 mg/kg of body mass of cellulose; CRE + PLA and PLA + PLA conditions) ingestion. After the loading period, changes in body mass were greater (p < .05) in the CRE (+0.87 ± 0.23 kg) than in the PLA group (+0.13 ± 0.27 kg). In both groups, peak power was higher (p = .01) in the CAF (1,033.4 ± 209.3 W) than in the PLA trial (1,003.3 ± 204.4 W), but mean power was not different between PLA and CAF trials (p > .05). In conclusion, CAF, but not CRE ingestion, increases anaerobic power. Conversely, neither CRE nor CAF has an effect on anaerobic capacity.

CGAs-Rich Conilon Coffee Consumption Improves Cognition and Reduces Oxidative Stress in Elderly with Alzheimer's Disease: A Pilot Study

BACKGROUND

The consumption of coffee has been associated with beneficial effects when it comes to Alzheimer's disease (AD). However, to the best of our knowledge, there are no studies on Conilon coffee consumption in elderly people with AD.

OBJECTIVE

Evaluate the effects of Conilon coffee consumption in elderly with AD.

METHODS

The study was carried out with 9 participants who consumed a minimum of 2 cups (200 mL cup) of Conilon coffee per day for 90 days. Cognitive assessment was done before (T0) and after 90 days (T90). Blood analysis was conducted at T0 and T90, as well as the assessment of advanced oxidation protein products (AOPP) and thiobarbituric acid reactive species (TBARS). The levels of chlorogenic acids and caffeine in the coffee beverage were quantified by liquid chromatography.

RESULTS

During the treatment, the participants consumed at least 550 mg and 540 mg of CGAs and caffeine, respectively. A significant improvement in cognition between T0 and T90 was observed as per MMSE, CTP, and clock drawing tests. Furthermore, there was a significant reduction in AOPP (37%) and TBARS (60%), indicating a reduction in oxidative stress. The consumption of the coffee did not significantly alter any blood parameter, which confirms the safety of the coffee treatment during the 90 days.

CONCLUSIONS

Our study demonstrated for the first time that regular consumption of coffee with high amounts of CGAs and caffeine improves cognitive functions and reduces oxidative stress, without altering blood parameters that indicate possible signs of toxicity in classical target organs.

Not Another Caffeine Effect on Sports Performance Study-Nothing New or More to Do?

The performance-enhancing potential of acute caffeine consumption is firmly established with benefits for many aspects of physical performance and cognitive function summarised in a number of meta-analyses. Despite this, there remains near exponential growth in research articles examining the ergogenic effects of caffeine. Many such studies are confirmatory of well-established ideas, and with a wealth of convincing evidence available, the value of further investigation may be questioned. However, several important knowledge gaps remain. As such, the purpose of this review is to summarise key knowledge gaps regarding the current understanding of the performance-enhancing effect of caffeine and justify their value for future investigation. The review will provide a particular focus on ten research priorities that will aid in the translation of caffeine's ergogenic potential to real-world sporting scenarios. The discussion presented here is therefore essential in guiding the design of future work that will aid in progressing the current understanding of the effects of caffeine as a performance enhancer.

How Repeatable Is the Ergogenic Effect of Caffeine? Limited Reproducibility of Acute Caffeine (3 mg.kg-1) Ingestion on Muscular Strength, Power, and Muscular Endurance

This study aimed to determine the effect of 3 mg.kg−1 acute caffeine ingestion on muscular strength, power and strength endurance and the repeatability of potential ergogenic effects across multiple trials. Twenty-two university standard male rugby union players (20 ± 2 years) completed the study. Using a double-blind, randomized, and counterbalanced within-subject experimental design. Participants completed six experimental trials (three caffeine and three placebo) where force time characteristic of the Isometric Mid-Thigh Pull (IMTP), Countermovement Jump (CMJ) and Drop Jumps (DJ) were assessed followed by assessments of Chest Press (CP), Shoulder Press (SP), Squats (SQ), and Deadlifts (DL) Repetitions Until Failure (RTF at 70% 1 RM). ANOVA indicated that caffeine improved both the CMJ and DJ (p < 0.044) and increased RTF in all RTF assessments (p < 0.002). When individual caffeine trials were compared to corresponding placebo trials, effect sizes ranged from trivial-large favoring caffeine irrespective of a main effect of treatment being identified in the ANOVA. These results demonstrate for the first time that the performance enhancing effects of caffeine may not be repeatable between days, where our data uniquely indicates that this is in part attributable to between sessions variation in caffeine’s ergogenic potential.

Effects of Caffeine on Performances of Simulated Match, Wingate Anaerobic Test, and Cognitive Function Test of Elite Taekwondo Athletes in Hong Kong

This study aimed to investigate the effects of caffeine on performances of simulated match, Wingate Anaerobic Test (WAnT), and cognitive function test of elite taekwondo athletes. Ten elite taekwondo athletes in Hong Kong volunteered to participate in two main trials in a randomized double-blinded crossover design. In each main trial, 1 h after consuming a drink with caffeine (CAF) or a placebo drink without caffeine (PLA), the participants completed two simulated taekwondo match sessions followed by the WAnT. The participants were instructed to complete three cognitive function tests, namely the Eriksen Flanker Test (EFT), Stroop Test, and Rapid Visual Information Processing Test, at baseline, before exercise, and immediately after the simulated matches. They were also required to wear functional near-infrared spectroscopy equipment during these tests. Before exercise, the reaction time in the EFT was shorter in the CAF trial than in the PLA trial (PLA: 494.9 ± 49.2 ms vs. CAF: 467.9 ± 38.0 ms, p = 0.035). In the WAnT, caffeine intake increased the peak power and mean power per unit of body weight (by approximately 13% and 6%, respectively, p = 0.018 & 0.042). The performance in the simulated matches was not affected by caffeine intake (p = 0.168). In conclusion, caffeine intake enhances anaerobic power and may improve certain cognitive functions of elite taekwondo athletes in Hong Kong. However, this may not be enough to improve the simulated match performance.

Can the Brazilian Caffeine Expectancy Questionnaires Differentiate the CYP1A2 and ADORA2A Gene Polymorphisms?-An Exploratory Study with Brazilian Athletes

This study investigated the ability of the Brazilian Caffeine Expectancy Questionnaire (CaffEQ-BR), full and brief versions, to differentiate genetic profiles regarding the polymorphisms of the CYP1A2 (rs 762551) and ADORA2A (rs 5751876) genes in a cohort of Brazilian athletes. One-hundred and fifty participants were genotyped for CYP1A2 and ADORA2A. After the recruitment and selection phase, 71 (90% male and 10% female, regular caffeine consumers) completed the CaffEQ-BR questionnaires and a self-report online questionnaire concerning sociodemographic data, general health status, and frequency of caffeine consumption. The order of completion of the CaffEQ-BR questionnaires was counterbalanced. The concordance between the full and brief versions of the CaffEQ-BR was analyzed using the intraclass correlation coefficient (ICC). To determine the discriminatory capacity of the questionnaires for genotype, the receiver operating characteristic (ROC) curve was applied for sensitivity and specificity (significance level of 5%). Mean caffeine intake was 244 ± 161 mg·day−1. The frequency of AA genotypes for CYP1A2 was 47.9% (n = 34) and 52.1% (n = 37) for C-allele carriers (AC and CC). The frequencies of TT genotypes for ADORA2A were 22.7% (n = 15) and 77.3% (n = 51) for C-allele carriers (TC and CC). All CaffEQ-BR factors, for the full and brief versions, were ICCs > 0.75, except for factor 6 (anxiety/negative effects; ICC = 0.60), and presented ROC curve values from 0.464 to 0.624 and 0.443 to 0.575 for CYP1A2 and ADORA2A. Overall, the CaffEQ-BR (full and brief versions) did not show discriminatory capacity for CYP1A2 and ADORA2A gene polymorphisms. In conclusion, the CaffEQ-BR was not able to differentiate genotypes for the CYP1A2 or ADORA2A genes in this group of Brazilian athletes.

The therapeutic potential of exercise and caffeine on attention-deficit/hyperactivity disorder in athletes

Attention-deficit/hyperactivity disorder (ADHD) is characterized by evident and persistent inattention, hyperactivity, impulsivity, and social difficulties and is the most common childhood neuropsychiatric disorder, and which may persist into adulthood. Seventy to 80% of children and adults with ADHD are treated with stimulant medication, with positive response rates occurring for both populations. Medicated ADHD individuals generally show sustained and improved attention, inhibition control, cognitive flexibility, on-task behavior, and cognitive performance. The ethics of ADHD medication use in athletics has been a debated topic in sport performance for a long time. Stimulants are banned from competition in accordance with World Anti-Doping Association and National Collegiate Athletic Association regulations, due to their ability to not only enhance cognitive performance but also exercise performance. Limited research has been conducted looking at the differences in exercise performance variables in unmedicated ADHD verses medicated ADHD. Not all ADHD athletes choose stimulant medication in their treatment plan due to personal, financial, or other reasons. Non-stimulant treatment options include non-stimulant medication and behavioral therapy. However, the use of caffeinated compounds and exercise has both independently been shown to be effective in the management of ADHD symptoms in human studies and animal models. This mini review will discuss the effect of exercise and caffeine on neurobehavioral, cognitive, and neurophysiological factors, and exercise performance in ADHD athletes, and whether exercise and caffeine should be considered in the treatment plan for an individual with ADHD.

The magical smell and taste: Can coffee be good to patients with cardiometabolic disease?

Coffee is a beverage consumed globally. Although few studies have indicated adverse effects, it is typically a beneficial health-promoting agent in a range of diseases, including depression, diabetes, cardiovascular disease, and obesity. Coffee is rich in caffeine, antioxidants, and phenolic compounds, which can modulate the composition of the gut microbiota and mitigate both inflammation and oxidative stress, common features of the burden of lifestyle diseases. This review will discuss the possible benefits of coffee on complications present in patients with diabetes, cardiovascular disease and chronic kidney disease, outwith the social and emotional benefits attributed to caffeine consumption.

Pharmaceutical and personal care products as emerging environmental contaminants in Nigeria: A systematic review

The increasingly broad and massive use of pharmaceuticals (human, veterinary) and personal care products in industrially developing nations makes their uncontrolled environmental and ecological impact a true concern. Focusing on Nigeria, this systematic literature search (databases: PubMed, ScienceDirect, Google Scholar, EMBASE, Scopus, Cochrane library and African Journals Online) aims to increase visibility to the issue. Among 275 articles identified, 7 were included in this systematic review. Studies indicated the presence of 11 personal care products (15.94 %) and 58 pharmaceutical products (84.06 %) in surface and ground water, leachates, runoffs, sludge, and sediments. The 42.86% (3/7) of reviewed studies reported 17 analgesics; 71.42 % (5/7) reported 16 antibiotics; 28.57 % (2/7) reported 5 lipid lowering drugs; 28.57% reported anti-malaria and fungal drugs; 14.29 % (1/7) reported estrogen drugs. Different studies report on sunscreen products, hormone, phytosterol, insect repellent, and β1 receptor. Gemfibrozil (<4-730 ng/L), Triclosan (55.1-297.7 ng/L), Triclocarban (35.6-232.4 ng/L), Trimethoprim (<1-388 ng/L) and Tramadol (<2-883 ng/L) had the highest range of concentrations. Findings confirm the need of i) legislation for environmental monitoring, including biota, ii) toxicological profiling of new market products, and iii) sensitization on appropriate use and disposal of pharmaceuticals and personal care products.

Effects of caffeine ingestion on cardiopulmonary responses during a maximal graded exercise test: a systematic review with meta-analysis and meta-regression

While the effects of caffeine ingestion on endurance performance are well known, its effects on cardiopulmonary responses during a maximal graded exercise test have been less explored. This study systematically reviewed and meta-analyzed studies investigating the effects of caffeine ingestion on cardiopulmonary responses during a maximal graded exercise test. A search was performed in four databases, and study quality was assessed using the PEDro scale. Data reported by the selected studies were pooled using random-effects meta-analysis, with selected moderator effects assessed via meta-regression. Twenty-one studies with good and excellent methodological quality were included in this review. Compared to placebo, caffeine increased peak minute ventilation (SMD = 0.33; p = 0.01) and time to exhaustion (SMD = 0.41; p = 0.01). However, meta-regression showed no moderating effects of dosage and timing of caffeine ingestion, stage length, or total length of GXT (all p > 0.05). Caffeine ingestion did not affect peak oxygen uptake (SMD = 0.13; p = 0.42), peak heart rate (SMD = 0.27; p = 0.07), peak blood lactate concentration (SMD = 0.60; p = 0.09), peak tidal volume (SMD = 0.10; p = 0.69), peak breathing frequency (SMD =0.20; p = 0.23), or peak power output (SMD = 0.22; p = 0.28). The results of this systematic review with meta-analysis suggest that caffeine increases time to exhaustion and peak minute ventilation among the cardiopulmonary variables assessed during GXT.

The Effect of Acute Caffeine Ingestion on Tactical Performance of Professional Soccer Players

In soccer, physical, tactical, and decision-making processes are highly important facets of successful performance. Caffeine has well established effects for promoting both physical and cognitive performance, but the translation of such benefits specifically for soccer match play is not well established. This study examined the effects of acute caffeine ingestion on tactical performance during small-sided games (SSG) in professional soccer players. Nineteen soccer players (22 ± 4 years) underwent a randomized, counterbalanced, crossover, double-blind placebo-controlled trial. The protocol consisted of 5 bouts of 5-min SSG with 3 players plus a goalkeeper in each team (3 + GK × 3 + GK) with each SSG separated by 1 min rest intervals. Tactical performance was assessed using the system of tactical assessment in soccer (FUT-SAT). Prior to each experimental trial, participants ingested caffeine (5 mg·kg⁻¹) or a placebo 60 min before the protocol. Overall, caffeine ingestion resulted in an increased ball possession time when compared to the placebo. When the offensive and defensive core principles were analyzed, the results were equivocal. Caffeine resulted in positive effects on some tactical decisions during the protocol, but it was deleterious or promoted no observed effect on other of the core tactical principles. Caffeine ingestion resulted in less offensive (during SSG3) and defensive (SSG 2, SSG3, and SSG4) errors. Caffeine ingestion also resulted in higher total offensive success during SSG 1 and SSG2, but it was detrimental during SSG3. Additionally, total defensive success was lower for the caffeine conditions during SSG 2 and SSG5 when compared to the placebo. In conclusion, caffeine influenced aspects of tactical decisions in soccer, resulting in fewer offensive and defensive errors, although it may be deleterious considering other tactical parameters. Future studies may clarify the effects of caffeine ingestion on specific decision-making parameters in soccer.

Acute effects of two caffeine doses on bar velocity during the bench press exercise among women habituated to caffeine: a randomized, crossover, double-blind study involving control and placebo conditions

PURPOSE

The main goal of this study was to evaluate the effectiveness of two different doses of caffeine (3 and 6 mg/kg) to enhance bar velocity during the bench press in women habituated to caffeine.

METHODS

Twelve recreationally trained women (age: 23.3 ± 0.8 years, body mass: 60.7 ± 5.7 kg, bench press one-repetition maximum (1RM): 44.3 ± 7.8 kg, daily caffeine ingestion: 5.7 ± 2.0 mg/kg/day) participated in a randomized double-blind experimental design. Each participant performed four different experimental sessions: after no supplementation (control, CON), after ingesting 3 and 6 mg/kg of caffeine (CAF-3 and CAF-6, respectively), or after ingesting a placebo (PLAC). In each experimental session, the participants performed 3 sets of 3 repetitions of the bench press exercise at 50% 1RM.

RESULTS

A two-way repeated-measures ANOVA with subsequent post hoc analyses indicated significant increases in peak velocity (p < 0.01; ES = 0.91) and mean velocity (p < 0.01; ES = 0.78) after the intake of CAF-6 compared to CON. The study did not show significant differences in bar velocity between CAF-6 and PLAC and between CAF-3 and PLAC. No significant differences in bar velocity were observed between CAF-3 and CAF-6 conditions.

CONCLUSION

These results suggest that 6 mg/kg of caffeine can be an effective dose to improve power-specific training outcomes in women habituated to caffeine. However, the ergogenic effect of 6 mg/kg of caffeine may be derived from a combination of biological effects and expectancy, as this dose was only superior to the control condition with no differences over the placebo.

Prevalence and correlates of highly caffeinated beverage consumption among Korean adolescents

OBJECTIVE

The purposes of this study were to (1) examine the multi-year prevalence of highly caffeinated beverage (HCB) consumption, (2) identify sex differences in the prevalence, and (3) investigate relationships between HCB consumption and behavioral characteristics in a nationally representative sample of Korean adolescents.

METHODS

Data from the Korea Youth Risk Behavior Web-based Survey (2014-2017) were analyzed.

RESULTS

HCB consumption was higher in 2017 than 2014 (23.9% vs. 12.0%), and higher among boys than girls (17.2% vs. 13.1%). HCB drinkers were more likely to (1) be boys, (2) be overweight or obese, (3) use alcohol and tobacco, (4) consume soda at least once per week, (5) consume sweetened beverages at least once per week, (6) have seriously considered suicide during the past 12 months, and (7) have attempted suicide during the past 12 months (p<0.05 for all).

CONCLUSION

Effective programs to curb HCB consumption among Korean adolescents need to be established.

The prevalence and practices of caffeine use as an ergogenic aid in English professional soccer

The ergogenic properties of caffeine are well established, with evidence supporting beneficial effects for physical and technical elements of performance required for successful soccer match play. Despite this, recommended caffeine practices for professional soccer have not been established. Therefore, the present study aimed to evaluate the use and behaviours surrounding caffeine use in elite English soccer clubs. Representatives of 36 clubs from the top four tiers of English professional football (40%) completed an online survey that sought to determine if, when, how and why caffeine was prescribed to players as a means of improving sports performance. Of the clubs sampled, 97% indicated that caffeine is provided to players as a means of improving performance. Caffeine is most commonly administered prior to (> 94%) and during a game (> 48%), with frequency uninfluenced by time of matches. There was a broad range and lack of consistency in the timing, dose and mode of caffeine administration, but doses were typically low. Evidence from the present study indicate a translational gap between science and practice, highlighting a need for future work to better understand how caffeine consumption can be optimised with respect to the specific demands and constraints in professional soccer.

Bibliometric Analysis of Studies on Coffee/Caffeine and Sport

This article provides an empirical overview of coffee/caffeine studies in relation to sport worldwide, an incipient but growing relationship that has existed since 1938, although systematized over time since 1999. The extracted articles were examined using a bibliometric approach based on data from 160 records stored in the Web of Science (JCR) between 1938 and August 2021, applying traditional bibliometric laws and using VOSviewer for data and metadata processing. Among the results, these articles highlight an exponential increase in scientific production in the last two decades, with a concentration in only 12 specific journals, the hegemony of the USA among the co-authorship networks of worldwide relevance, and the thematic and temporal segregation of the concepts under study. This article concludes a high fragmentation of the authors with the highest level of scientific production and an evolution of almost 20 years in relevant thematic topics, and a concurrent concentration in three large blocks: (1) coffee consumption and risk factors, (2) health and coffee consumption, and (3) metabolism and sport correlated with the intake of coffee, which are distanced in time, providing evidence of an evolution that gives way to the irruption of alternative visions in the relationship of coffee and caffeine with sport.

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.

Is Coffee a Useful Source of Caffeine Preexercise?

Caffeine is a well-established ergogenic aid, with its performance-enhancing effects demonstrated across a wide variety of exercise modalities. Athletes tend to frequently consume caffeine as a performance enhancement method in training and competition. There are a number of methods available as a means of consuming caffeine around exercise, including caffeine anhydrous, sports drinks, caffeine carbohydrate gels, and gum. One popular method of caffeine ingestion in nonathletes is coffee, with some evidence suggesting it is also utilized by athletes. In this article, we discuss the research pertaining to the use of coffee as an ergogenic aid, exploring (a) whether caffeinated coffee is ergogenic, (b) whether dose-matched caffeinated coffee provides a performance benefit similar in magnitude to caffeine anhydrous, and (c) whether decaffeinated coffee consumption affects the ergogenic effects of a subsequent isolated caffeine dose. There is limited evidence that caffeinated coffee has the potential to offer ergogenic effects similar in magnitude to caffeine anhydrous; however, this requires further investigation. Coingestion of caffeine with decaffeinated coffee does not seem to limit the ergogenic effects of caffeine. Although caffeinated coffee is potentially ergogenic, its use as a preexercise caffeine ingestion method represents some practical hurdles to athletes, including the consumption of large volumes of liquid and difficulties in quantifying the exact caffeine dose, as differences in coffee type and brewing method may alter caffeine content. The use of caffeinated coffee around exercise has the potential to enhance performance, but athletes and coaches should be mindful of the practical limitations.

Is caffeine mouth rinsing an effective strategy to improve physical and cognitive performance? A systematic review

The aim of this study was to perform a systematic review on the effects of caffeine mouth rinsing on physical and cognitive performance. Following a search through 4 databases, 18 studies were found meeting the inclusion criteria (15 for physical performance and 3 for cognitive performance). All selected studies found an improvement in cognitive performance with caffeine mouth rinse. Four studies found positive effects of caffeine mouthwash on physical performance when repeated during exercise, while one study detected a positive effect with a single mouthwash before exercise, but only in a fasted state. Among these studies that showed positive effects, however, three (2 for physical performance and 1 for cognitive performance) presented fair methodological quality. There was also a variety of methodological approaches in the studies that showed no improvement in physical performance with caffeine mouth rinse, which may have influenced the potential to detect the ergogenic effect of caffeine mouth rinse. Thus, the effects of caffeine mouth rinse on physical performance are mixed, but a potential ergogenic effect might be present in a fasted state and when mouthwash is repeated during exercise. Concerning cognitive performance, caffeine mouth rinse seems to be a beneficial strategy.

Brief Version of Caffeine Expectancy Questionnaire in Brazil

The use of extensive questionnaires has the limitation of filling time bias, related to the ability to focus and accurately respond to many items, justifying the necessity for a brief version. This study aimed to build a brief version of the Caffeine Expectancy Questionnaire in Brazil (B-CaffEQ-BR) composed of 21 items divided into seven factors, with as adequate consistency and reproducibility as the full version. Quantitative procedures using statistical modeling were applied using the CaffEQ-BR (full version) database keeping the Mean Absolute Error (MAE) (based on the full version) <0.5 and Cronbach's α and Intraclass Correlation Coefficient (ICC) ≥0.7. The expert panel (n = 3), in a blind design, evaluated the semantic structuring within the options indicated by previous statistical modeling until the agreement of the expert panel. The participants (n = 62), Brazilian adults who were regular caffeine consumers (175.8 ± 94.4 mg/day), of whom 62.9% were women, 33.1 ± 9.7 years, 24.5 ± 3.8 kg/m², and 62.9% of whom self-identified as white, were asked to respond twice to the online questionnaire in 48-72 h. The first sample (n = 40) tested interobserver reproducibility with the double application of B-CaffEQ-BR. Another sample (n = 22) answered the CaffEQ-BR (full version) and B-CaffEQ-BR, and the last sample (n = 18) performed the reverse process. The B-CaffEQ-BR presented excellent internal consistency (Cronbach's α ≥ 0.729) and overall reproducibility (ICC ≥ 0.915) for the entire questionnaire and its seven factors. The B-CaffEQ-BR can be a valuable tool in caffeine research with the Brazilian adult population.

Habitual Caffeine Consumption Does Not Interfere With the Acute Caffeine Supplementation Effects on Strength Endurance and Jumping Performance in Trained Individuals

The long-standing caffeine habituation paradigm was never investigated in strength endurance and jumping exercise performance through a straightforward methodology. The authors examined if habitual caffeine consumption would influence the caffeine ergogenic effects on strength endurance and jumping performance as well as perceptual responses. Thirty-six strength-trained individuals were mathematically allocated into tertiles according to their habitual caffeine consumption: low (20 ± 11 mg/day), moderate (88 ± 33 mg/day), and high consumers (281 ± 167 mg/day). Then, in a double-blind, crossover, counterbalanced fashion, they performed a countermovement vertical jump test and a strength endurance test either after caffeine (6 mg/kg) and placebo supplementation or after no supplementation (control). Perceptual responses such as ratings of perceived exertion and pain were measured at the termination of the exercises. Acute caffeine supplementation improved countermovement vertical jump performance (p = .001) and total repetitions (p = .004), regardless of caffeine habituation. Accordingly, analysis of absolute change from the control session showed that caffeine promoted a significantly greater improvement in both countermovement vertical jump performance (p = .004) and total repetitions (p = .0001) compared with placebo. Caffeine did not affect the rating of perceived exertion and pain in any exercise tests, irrespective of tertiles (for all comparisons, p > .05 for both measures). Caffeine side effects were similar in low, moderate, and high caffeine consumers. These results show that habitual caffeine consumption does not influence the potential of caffeine as an ergogenic aid in strength endurance and jumping exercise performance, thus challenging recommendations to withdraw from the habitual caffeine consumption before supplementing with caffeine.

Placebo Effect of Caffeine on Substrate Oxidation during Exercise

By using deceptive experiments in which participants are informed that they received caffeine when, in fact, they received an inert substance (i.e., placebo), several investigations have demonstrated that exercise performance can be enhanced to a similar degree as a known caffeine dose. This 'placebo effect' phenomenon may be part of the mechanisms explaining caffeine's ergogenicity in exercise. However, there is no study that has established whether the placebo effect of caffeine is also present for other benefits obtained with acute caffeine intake, such as enhanced fat oxidation during exercise. Therefore, the aim of this investigation was to investigate the placebo effect of caffeine on fat oxidation during exercise. Twelve young men participated in a deceptive double-blind cross-over experiment. Each participant completed three identical trials consisting of a step incremental exercise test from 30 to 80% of V.O_2max. In the two first trials, participants ingested either 3 mg/kg of cellulose (placebo) or 3 mg/kg of caffeine (received caffeine) in a randomized order. In the third trial, participants were informed that they had received 3 mg/kg of caffeine, but a placebo was provided (informed caffeine). Fat oxidation rates were derived from stoichiometric equations. In received caffeine, participants increased their rate of fat oxidation over the values obtained with the placebo at 30%, 40%, 50%, and 60% of V.O_2max (all p < 0.050). In informed caffeine, participants increased their rate of fat oxidation at 30%, 40%, 50% 60%, and 70% of V.O_2max (all p < 0.050) over the placebo, while there were no differences between received versus informed caffeine. In comparison to placebo (0.32 ± 0.15 g/min), the rate of maximal fat oxidation was higher in received caffeine (0.44 ± 0.22 g/min, p = 0.045) and in informed caffeine (0.41 ± 0.20 g/min, p = 0.026) with no differences between received versus informed caffeine. However, the intensity at which maximal fat oxidation rate was obtained (i.e., Fat_max) was similar in placebo, received caffeine, and informed caffeine trials (42.5 ± 4.5, 44.2 ± 9.0, and 41.7 ± 10.5% of V.O_2max, respectively, p = 0.539). In conclusion, the expectancy of having received caffeine produced similar effects on fat oxidation rate during exercise than actually receiving caffeine. Therefore, the placebo effect of caffeine is also present for the benefits of acute caffeine intake on substrate oxidation during exercise and it may be used to enhance fat oxidation during exercise in participants while reducing any risks to health that this substance may have.

Perceived exertion and performance modulation: effects of caffeine ingestion and subject expectation

BACKGROUND

It is well established that caffeine has ergogenic effects on endurance performance. This evidence often comes from studies in which subjects receive either caffeine or placebo in double-blind, randomized and counterbalanced order. Here, we propose a new methodology which aims to estimate the effects of participant expectancy of ergogenic or anti-ergogenic effects on performance.

METHODS

Sixteen physically active participants (non-athletes engaged in systematic physical training >3 months, at least three times a week) performed three 30-minute running tests after being told they would be provided with either a harmful treatment (lactic acid), a beneficial treatment (caffeine) or a placebo. In each blinded case, subjects were given caffeine. The velocity and Rating of Perceived Exertion (RPE) during the time trial were examined in light of the participant's expectancy before and after the endurance event using Bayesian multilevel models.

RESULTS

For pre-exercise expectancy, there is a 92% probability that caffeine expectation decreases RPE (posterior median±SD -0.65±0.36) and a 79% probability that lactic acid expectation increases RPE (posterior median±SD 0.58±0.47) with expectations for placebo and 'not sure' falling in between (posterior median±SD: -0.37±0.32 and -0.22±0.37, respectively). In general, our interventions suggest an 81% probability that caffeine lowers RPE. However, there was no effect of caffeine supplementation on running velocity (median±SD 0.04±0.08 km.h^-1).

CONCLUSIONS

When a participant believed they are under a potentially positive treatment, their RPE decreased but if they believed themselves to be under a harmful treatment, their RPE increased, regardless of the actual positive intervention; neither caffeine nor the expectancy of a particular intervention improved actual performance as measured by running velocity in a 30-minute period.

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 Ingestion Improves Performance During Fitness Tests but Does Not Alter Activity During Simulated Games in Professional Basketball Players

PURPOSE

To examine the effects of acute caffeine supplementation on physical performance during fitness testing and activity during simulated games in basketball players.

METHODS

A double-blind, counterbalanced, randomized, crossover study design was followed. A total of 14 professional male basketball players ingested a placebo (sucrose) and caffeine (6 mg·kg-1 of body mass) in liquid form prior to completing 2 separate testing sessions. Each testing session involved completion of a standardized 15-minute warm-up followed by various fitness tests including 20-m sprints, countermovement jumps, Lane Agility Drill trials, and a repeated-sprint-ability test. Following a 20-minute recovery, players completed 3 × 7-minute 5-vs-5 simulated periods of full-court basketball games, each separated by 2 minutes of recovery. Local positioning system technology was used to measure player activity during games. Players completed a side-effects questionnaire 12 to 14 hours after testing.

RESULTS

Players experienced significant (P < .05), moderate-very large (effect size = -2.19 to 0.89) improvements in 20-m sprint, countermovement jump, Lane Agility Drill, and repeated-sprint-ability performance with caffeine supplementation. However, external workloads completed during simulated games demonstrated nonsignificant, trivial-small (effect size = -0.23 to 0.12) changes between conditions. In addition, players reported greater (P < .05) insomnia and urine output after caffeine ingestion.

CONCLUSIONS

Acute caffeine supplementation could be effective to improve physical performance during tests stressing fitness elements important in basketball. However, acute caffeine supplementation appears to exert no meaningful effects on the activity completed during simulated basketball games and may promote sleep disturbances and exert a diuretic effect when taken at 6 mg·kg-1 of body mass in professional players.

Placebo Effect of Caffeine on Maximal Strength and Strength Endurance in Healthy Recreationally Trained Women Habituated to Caffeine

BACKGROUND

By using deceptive experimental designs, several investigations have observed that trained individuals may increase their performance when told they were given caffeine, when in fact they received a placebo (i.e., the placebo effect of caffeine). However, most of these investigations on the placebo effect of caffeine used individuals with low caffeine consumption or did not report habitual caffeine consumption, especially in studies analyzing resistance-based exercise. Hence, it is unknown if habitual caffeine consumers benefit from the placebo effect of caffeine on exercise performance. Thus, the aim of the present study was to analyze the placebo effect of caffeine on maximal strength and strength-endurance performance during the bench press exercise (BP) in women with mild-moderate daily consumption of caffeine.

METHODS

Thirteen resistance-trained women (BP one-repetition maximum (1RM) = 40.0 ± 9.7 kg) habituated to caffeine (4.1 ± 1.7 mg/kg/day) completed a deceptive randomized experimental design with two experimental trials. On one occasion, participants were told that they would receive 6 mg/kg of caffeine but received a placebo (PLAC), and on other occasions, participants did not receive any substance and were told that this was a control situation (CONT). In each experimental trial, participants underwent a 1RM BP test and a strength-endurance test consisting of performing the maximal number of repetitions at 50% of their 1RM.

RESULTS

In comparison to CONT, PLAC did not enhance 1RM (40.0 ± 10.5 kg vs. 41.0 ± 9.5 kg, respectively; p = 0.10), nor did it enhance the number of repetitions (32.2 ± 5.1 vs. 31.8 ± 4.5; p = 0.66) or mean power (130 ± 34 vs. 121 ± 26; p = 0.08) in the strength-endurance test.

CONCLUSION

Informing participants that they were given caffeine, when in fact they received a placebo, did not modify any performance variable measured in this investigation. Thus, the use of the placebo effect of caffeine seemed an ineffective strategy to enhance muscle strength and strength endurance during the BP exercise in women with mild-moderate consumption of caffeine.

Caffeine Effect on Cognitive Function during a Stroop Task: fNIRS Study

Acting as a brain stimulant, coffee resulted in heightening alertness, keeping arousal, improving executive speed, maintaining vigilance, and promoting memory, which are associated with attention, mood, and cognitive function. Functional near-infrared spectroscopy (fNIRS) is a noninvasive optical method to monitor brain activity by measuring the absorption of the near-infrared light through the intact skull. This study is aimed at acquiring brain activation during executing task performance. The aim is to explore the effect of coffee on cognitive function by the fNIRS neuroimaging method, particularly on the prefrontal cortex regions. The behavioral experimental results on 31 healthy subjects with a Stroop task indicate that coffee can easily and effectively modulate the execute task performance by feedback information of the response time and accuracy rate. The findings of fNIRS showed that apparent hemodynamic changes were detected in the bilateral VLPFC regions and the brain activation regions varied with different coffee conditions.

Caffeine Timing Improves Lower-Body Muscular Performance: A Randomized Trial

Little is known about the optimal time to consume caffeine prior to exercise to maximize the ergogenic benefits of the substance.

Purpose: To determine the optimal pre-exercise time interval to consume caffeine to improve lower-body muscular performance. A secondary aim was to identify the presence of any sex differences in responses to timed caffeine administration.

Methods: Healthy, resistance-trained males (n = 18; Mean±SD; Age: 25.1 ± 5.7 years; Height: 178.4 ± 7.1 cm; Body mass: 91.3 ± 13.5 kg; Percent body fat: 20.7 ± 5.2; Average caffeine consumption: 146.6 ± 100.3 mg/day) and females (n = 11; Mean ± SD; Age: 20.1 ± 1.6 years; Height: 165.0 ± 8.8 cm; Body mass: 65.8 ± 10.0 kg; Percent bodyfat: 25.8 ± 4.2; Average caffeine consumption: 111.8 ± 91.7 mg/day) participated in this investigation. In a randomized, double-blind, placebo-controlled, crossover fashion, participants consumed 6 mg·kg⁻¹ caffeine or placebo solution at three time points: 2 h prior (2H), 1 h prior (1H), or 30 min prior (30M) to exercise testing. During three visits, caffeine was randomly administered at one time point, and placebo was administered at the other two time points. During one visit, placebo was administered at all three time points. Next, participants performed isometric mid-thigh pulls (IMTP), countermovement vertical jumps (CMVJ), and isometric/isokinetic knee extensor testing (ISO/ISOK).

Results: Caffeine administered at 1H significantly improved absolute CMVJ and ISO performance relative to placebo. Mean CMVJ jump height was significantly higher during 1H compared to 30M. However, only caffeine administered at 30M significantly improved absolute measures of isokinetic performance. Analysis of the pooled caffeine conditions revealed that muscular performance was more consistently augmented by caffeine in males compared to females.

Conclusions: Pre-exercise caffeine timing significantly modulated participant responses to the substance, with 1H exerting the most consistent ergogenic benefits relative to other time points, particularly compared to 2H. Male participants were found to respond more consistently to caffeine compared to female participants. These results suggest that active individuals can maximize the ergogenic effects of caffeine by consuming the substance ~1 h prior to the point when peak muscular performance is desired.

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.

Effects of Caffeine on Event-Related Potentials and Neuropsychological Indices After Sleep Deprivation

Objective: Caffeine is a central nervous system stimulant that can effectively alleviate brain fatigue and low cognitive efficiency induced by total sleep deprivation (TSD). Recent studies have demonstrated that caffeine can improve subjective attention and objective behavioral metrics, such as arousal level, reaction time, and memory efficiency. However, only a few studies have examined the electrophysiological changes caused by the caffeine in humans following sleep disturbance. In this study, an event-related potential (ERP) technique was employed to measure the behavioral, cognitive, and electrophysiological changes produced by caffeine administration after TSD.

Methods: Sixteen healthy subjects within-subject design performed a visual Go/No-Go task with simultaneous electroencephalogram recording. Behavioral and ERP data were evaluated after 36 h of TSD, and the effects of ingestion of either 400 mg of caffeine or placebo were compared in a double-blind randomized design.

Results: Compared with placebo administration, the Go hit rates were significantly enhanced in the caffeine condition. A simple effect analysis revealed that, compared with baseline, the Go-P2 amplitude was significantly enhanced after TSD in the caffeine consumption condition. A significant main effect of the drug was found on No-Go-P2, No-Go-N2 amplitude, and Go-P2 latency before and after TSD.

Conclusion: Our findings indicate that caffeine administration has acute effects on improving the efficiency of individual automatic reactions and early cognitive processes. Caffeine was related to the preservation of an individual’s arousal level and accelerated response-related decisions, while subjects’ higher-level recognition had limited improvement with prolonged awareness.

Translation and Validation of the Caffeine Expectancy Questionnaire in Brazil (CaffEQ-BR)

Caffeine is the world's most commonly used stimulant of the central nervous system. Caffeine is present in coffee and other beverages such as tea, soft drinks, and cocoa-based foods. The caffeine expectancy questionnaire was developed to investigate the effects of caffeine expectations and thus contribute to knowledge about its usage and subjective effects (response expectancies). This study aimed to evaluate caffeine expectation psychometrically in a sample of the Brazilian population. The original version of the "Caffeine Expectancy Questionnaire (CaffEQ)" was translated and validated into Brazilian-Portuguese and adapted to Brazilian culture to be used in the Brazilian adult (19-59 y) population. After the translation and back-translation processes of the original CaffEQ questionnaire, the content and semantic validation were performed by a group of experts. The Brazilian-Portuguese version of the questionnaire consists of 47 items, in seven factors, which assess subjective perceptions about the effects of caffeine. Interobserver reproducibility and internal consistency of the questionnaire were tested with a convenience sample (n = 50) of Brazilian adult consumers of caffeine sources, who completed the Brazilian CaffEQ (CaffEQ-BR) on two occasions separated by 24 h. All of the 47 questions were adequate regarding reliability, clarity, and comprehension. Psychometric properties could be replicated consistently. Appropriate internal consistency and validation were confirmed by Cronbach's alpha (α) 0.948, and an intraclass correlation coefficient of 0.976 was observed. The CaffEQ-BR was applied using a web-based platform to a convenience sample of Brazilian adults from all 27 Brazilian states (n = 4202 participants), along with measures of sociodemographic and caffeine consumption data. Factor validity was verified by confirmatory factor analysis. The seven factors presented a good fit for Root Mean Square Error of Approximation-RMSEA = 0.0332 (95% CI: 0.0290-0.0375). By confirming the validity and reliability of CaffEQ-BR, a useful tool is now available to assess caffeine expectations in the Brazilian adult population.

Caffeine and Exercise: What Next?

Caffeine is a widely utilized performance-enhancing supplement used by athletes and non-athletes alike. In recent years, a number of meta-analyses have demonstrated that caffeine's ergogenic effects on exercise performance are well-established and well-replicated, appearing consistent across a broad range of exercise modalities. As such, it is clear that caffeine is an ergogenic aid-but can we further explore the context of this ergogenic aid in order to better inform practice? We propose that future research should aim to better understand the nuances of caffeine use within sport and exercise. Here, we propose a number of areas for exploration within future caffeine research. These include an understanding of the effects of training status, habitual caffeine use, time of day, age, and sex on caffeine ergogenicity, as well as further insight into the modifying effects of genotype. We also propose that a better understanding of the wider, non-direct effects of caffeine on exercise, such as how it modifies sleep, anxiety, and post-exercise recovery, will ensure athletes can maximize the performance benefits of caffeine supplementation during both training and competition. Whilst not exhaustive, we hope that the questions provided within this manuscript will prompt researchers to explore areas with the potential to have a large impact on caffeine use in the future.

Effects of Expectancy on Cognitive Performance, Mood, and Psychophysiology in Healthy Adolescents and Their Parents in an Experimental Study

OBJECTIVE

Placebo effects on cognitive performance and mood and their underlying mechanisms have rarely been investigated in adolescents. Therefore, the following hypotheses were investigated with an experimental paradigm: (1) placebo effects could be larger in adolescents than in adults, (2) parents' expectations influence their adolescents' expectations and placebo effects, and (3) a decrease in stress levels could be an underlying mechanism of placebo effects.

METHODS

Twenty-six healthy adolescents (13.8 ± 1.6 years, 14 girls) each with a parent (45.5 ± 4.2 years, 17 mothers) took part in an experimental within-subjects study. On two occasions, a transdermal patch was applied to their hips and they received an envelope containing either the information that it is a Ginkgo patch to improve cognitive performance and mood, or it is an inactive placebo patch, in counterbalanced order. Cognitive performance and mood were assessed with a parametric Go/No-Go task (PGNG), a modification of California Verbal Learning Test, and Profile of Mood Scales (POMS). Subjects rated their expectations about Ginkgo's effects before patch application as well as their subjective assessment of its effects after the tests. An electrocardiogram and skin conductance levels (SCLs) were recorded and root mean square of successive differences (RMSSD), high-frequency power (HF), and the area under the curve of the SCL (AUC) were analyzed as psychophysiological stress markers.

RESULTS

Expectations did not differ between adolescents and parents and were correlated concerning reaction times only. Overall, expectations did not influence placebo effects. There was only one significant placebo effect on the percentage of correct inhibited trials in one level of the PGNG in adolescents, but not in parents. RMSSD and HF significantly increased, and AUC decreased from pre- to post-patch application in adolescents, but not in parents.

CONCLUSION

With this experimental paradigm, we could not induce relevant placebo effects in adolescents and parents. This could be due to aspects of the study design such as application form and substance, and that healthy subjects were employed. Nevertheless, we could show that adolescents are more sensitive to psychophysiological reactions related with interventions which could be part of the underlying mechanisms of placebo effects in adolescents.

Caffeine Increased Muscle Endurance Performance Despite Reduced Cortical Activation and Unchanged Neuromuscular Efficiency and Corticomuscular Coherence

The central and peripheral effects of caffeine remain debatable. We verified whether increases in endurance performance after caffeine ingestion occurred together with changes in primary motor cortex (MC) and prefrontal cortex (PFC) activation, neuromuscular efficiency (NME), and electroencephalography–electromyography coherence (EEG–EMG coherence). Twelve participants performed a time-to-task failure isometric contraction at 70% of the maximal voluntary contraction after ingesting 5 mg/kg of caffeine (CAF) or placebo (PLA), in a crossover and counterbalanced design. MC (Cz) and PFC (Fp1) EEG alpha wave and vastus lateralis (VL) muscle EMG were recorded throughout the exercise. EEG–EMG coherence was calculated through the magnitude squared coherence analysis in MC EEG gamma-wave (CI > 0.0058). Moreover, NME was obtained as the force–VL EMG ratio. When compared to PLA, CAF improved the time to task failure (p = 0.003, d = 0.75), but reduced activation in MC and PFC throughout the exercise (p = 0.027, d = 1.01 and p = 0.045, d = 0.95, respectively). Neither NME (p = 0.802, d = 0.34) nor EEG–EMG coherence (p = 0.628, d = 0.21) was different between CAF and PLA. The results suggest that CAF improved muscular performance through a modified central nervous system (CNS) response rather than through alterations in peripheral muscle or central–peripheral coupling.

The Influence of Caffeine Expectancies on Simulated Soccer Performance in Recreational Individuals

Caffeine (CAF) has been reported to improve various facets associated with successful soccer play, including gross motor skill performance, endurance capacity and cognition. These benefits are primarily attributed to pharmacological mechanisms. However, evidence assessing CAF's overall effects on soccer performance are sparse with no studies accounting for CAF's potential psychological impact. Therefore, the aim of this study was to assess CAF's psychological vs. pharmacological influence on various facets of simulated soccer performance. Utilising a double-dissociation design, eight male recreational soccer players (age: 22 ± 5 years, body mass: 78 ± 16 kg, height: 178 ± 6 cm) consumed CAF (3 mg/kg/body mass) or placebo (PLA) capsules, 60 minutes prior to performing the Loughborough Intermittent Shuttle Test (LIST) interspersed with a collection of ratings of perceived exertion (RPE), blood glucose and lactate, heart rate and performing the Loughborough Soccer Passing Test (LSPT). Whole-body dynamic reaction time (DRT) was assessed pre- and post- LIST, and endurance capacity (T_LIM) post, time-matched LIST. Statistical analysis was performed using IBM SPSS (v24) whilst subjective perceptions were explored using template analysis. Mean T_LIM was greatest (p < 0.001) for synergism (given CAF/told CAF) (672 ± 132 s) vs. placebo (given PLA/told PLA) (533 ± 79 s). However, when isolated, T_LIM was greater (p = 0.012) for CAF psychology (given PLA/told CAF) (623 ± 117 s) vs. pharmacology (given CAF/told PLA) (578 ± 99 s), potentially, via reduced RPE. Although DRT performance was greater (p = 0.024) post-ingestion (+5 hits) and post-exercise (+7 hits) for pharmacology vs. placebo, psychology and synergism appeared to improve LSPT performance vs. pharmacology. Interestingly, positive perceptions during psychology inhibited LSPT and DRT performance via potential CAF over-reliance, with the opposite occurring following negative perceptions. The benefits associated with CAF expectancies may better suit tasks that entail lesser cognitive-/skill-specific attributes but greater gross motor function and this is likely due to reduced RPE. In isolation, these effects appear greater vs. CAF pharmacology. However, an additive benefit may be observed after combining expectancy with CAF pharmacology (i.e. synergism).

Theobromine Improves Working Memory by Activating the CaMKII/CREB/BDNF Pathway in Rats

Theobromine (TB) is a primary methylxanthine found in cacao beans. cAMP-response element-binding protein (CREB) is a transcription factor, which is involved in different brain processes that bring about cellular changes in response to discrete sets of instructions, including the induction of brain-derived neurotropic factor (BDNF). Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) has been strongly implicated in the memory formation of different species as a key regulator of gene expression. Here we investigated whether TB acts on the CaMKII/CREB/BDNF pathway in a way that might improve the cognitive and learning function in rats. Male Wistar rats (5 weeks old) were divided into two groups. For 73 days, the control rats (CN rats) were fed a normal diet, while the TB-fed rats (TB rats) received the same food, but with a 0.05% TB supplement. To assess the effects of TB on cognitive and learning ability in rats: The radial arm maze task, novel object recognition test, and Y-maze test were used. Then, the brain was removed and the medial prefrontal cortex (mPFC) was isolated for Western Blot, real-time PCR and enzyme-linked immunosorbent assay. Phosphorylated CaMKII (p-CaMKII), phosphorylated CREB (p-CREB), and BDNF level in the mPFC were measured. In all the behavior tests, working memory seemed to be improved by TB ingestion. In addition, p-CaMKII and p-CREB levels were significantly elevated in the mPFC of TB rats in comparison to those of CN rats. We also found that cortical BDNF protein and mRNA levels in TB rats were significantly greater than those in CN rats. These results suggest that orally supplemented TB upregulates the CaMKII/CREB/BDNF pathway in the mPFC, which may then improve working memory in rats.

Caffeine and resistance exercise: the effects of two caffeine doses and the influence of individual perception of caffeine

Although caffeine is a widely used ergogenic resource, some information regarding its effects on resistance exercises is still lacking. The objective of the present study was to verify the acute effect of the ingestion of two different doses of caffeine on performance during a session of resistance exercises and to analyze the perception of the subjects in relation to the intake of caffeine. Following a double-blind, randomised, cross-over, controlled, and non-placebo design, 14 trained and healthy men (24.7 ± 6.8 years; 79.8 ± 9.8 kg; 177.3 ± 8.5 cm) performed a training session in chest-press, shoulder-press, and biceps curl exercises (3 sets until exhaustion; 70% 1RM; 3 min rest interval; 2 s for each concentric and eccentric phase) on three non-consecutive days after ingestion of 3 mg.kg^-1 caffeine (CAF3), 6 mg.kg^-1 caffeine (CAF6), or no substance (CON). Subjects were informed that one of the caffeine doses would be placebo. The total number of repetitions performed in CON (93.6 ± 22.4) was significantly lower than in CAF3 (108.0 ± 19.9, P = 0.02) and in CAF6 (109.3 ± 19.8, P = 0.03) and there were no differences between caffeine doses. Eight subjects noticed that caffeine was in CAF3 and six in CAF6 and there were no differences in the number of repetitions between sessions in which the subjects perceived and did not perceive caffeine. In conclusion, caffeine doses of 3 or 6 mg.kg^-1 similarly increased performance in resistance upper limb exercises, independent of the subject's perception of substance ingestion.