Exercise and sport performance with low doses of caffeine

Acute, dose-response effects of guayusa leaf extract on mood, cognitive and motor-cognitive performance, and blood pressure, heart rate, and ventricular repolarization

PURPOSE

We conducted a randomized, double-blind, placebo-controlled crossover trial in young adults to examine the dose-dependent (600 mg versus 1200 mg), acute effects of consumption of an Ilex guayusa tea extract (GLE) on mood, cognitive and motor-cognitive performance, as well as its acute cardiovascular effects.

METHODS

Twenty-five adults (mean ± SD, age = 28 ± 7 y; 9 M/16 F) completed familiarization and then three randomly ordered experimental visits where they consumed either 600 mg (GLE600) or 1200 mg (GLE1200) GLE or placebo (PLA). Following supplement consumption, participants completed a mood state survey, assessments of perceived jitteriness, energy, and focus, and neurocognitive and motor-cognitive testing. Blood pressure (BP), heart rate, and QT interval length were determined before and after supplementation.

RESULTS

GLE600 significantly improved total mood disturbance (mean ± SE difference = -6.9 ± 2.6 au, p = 0.034), fatigue-inertia (-2.84 ± 0.89 au, p = 0.008), perceived energy (+13.00 ± 4.49 au; p = 0.02), motor speed (+4.52 ± 1.42 au, p = 0.008), and psychomotor speed (+7.20 ± 2.16 au, p = 0.005) relative to PLA. GLE1200 also improved psychomotor speed (+5.08 ± 2.16 ms, p = 0.045) and uniquely increased motor-cognitive performance as reflected by a decrease in reaction time (-0.106 ± 0.04 ms, p = 0.026) during a neurocognitive hop test. The effect of GLE on jitteriness was both dose- and sex-dependent. Jitteriness increased with increasing GLE dose in women only (p < 0.001). Both GLE600 and GLE1200 similarly increased systolic and diastolic BP by 4-5 mmHg (p ≤ 0.022). Neither GLE600 nor GLE1200 acutely influenced QTc length (p = 0.31).

CONCLUSIONS

The goal of GLE supplementation should be considered when selecting a dosing strategy. Lower dosages of GLE (e.g. 600 mg) appear to optimize cognitive and mood-related outcomes while limiting side-effects such as jitteriness in women, and higher dosages may be necessary (e.g. 1200 mg) to promote improvements in motor-cognitive performance.

A randomized placebo controlled trial demonstrates the effect of dl-methylephedrine on brain functions is weaker than that of pseudoephedrine

Intellectual drug doping in athletics by using stimulants that affect central nervous system functions has been diversified. Stimulants are regulated by the World Anti-Doping Agency according to their levels of urinary concentration. Positron emission tomography could evaluate how stimulants affect central nervous system functions. We aimed to evaluate the effect of stimulants on brain function by examining the difference in brain dopamine transporter occupancy by PET after administration of dl-methylephedrine or pseudoephedrine at the clinical maximum daily dose. Four PET scans without and with drug administration (placebo, dl-methylephedrine 150 mg and pseudoephedrine 240 mg) were performed. The concentrations of dl-methylephedrine and pseudoephedrine in plasma and urine were measured. DAT occupancies in the striatum with placebo, dl-methylephedrine and pseudoephedrine were calculated by PET images. The urinary concentration of dl-methylephedrine (12.7 µg/mL) exceeded the prohibited concentration (10 µg/mL), but the DAT occupancy with dl-methylephedrine (6.1%) did not differ (p = 0.92) from that with placebo (6.2%). By contrast, although the urinary concentration of pseudoephedrine (144.8 µg/mL) was below the prohibited concentration (150 μg/mL), DAT occupancy with pseudoephedrine was 18.4%, which was higher than that with placebo (p = 0.009). At the maximum clinical dose, dl-methylephedrine was shown to have weaker effects on brain function than pseudoephedrine.

Effects of different doses of caffeine on cognitive performance in healthy physically active individuals

PURPOSE

Caffeine is a potent central nervous system stimulant that increases the activity of the prefrontal cortex and can improve various cognitive skills. An improvement in these cognitive skills can lead to further benefits in athletic performance. Therefore, it is necessary to clarify the dose-response of caffeine on cognitive performance. This study aimed to determine the effects of different doses of caffeine on sport-related cognitive aspects.

METHODS

Twenty-nine healthy physically active young adults were recruited. All participants completed three trials under the following conditions: (a) placebo, (b) 3 mg/kg, or (c) 6 mg/kg body mass of caffeine. In each trial, different cognitive abilities were evaluated with the following battery of tests: reaction time (Dynavision™ D2), anticipation (Bassin Anticipation Timer), sustained attention (Go/No-Go and Eriksen Flanker Test) and memory tests. Moreover, the side effects and the perceived sensation index were recorded 24 h after each test.

RESULTS

Reaction time only improved following 6 mg/kg of caffeine intake (Physical reaction time: -0.04 s, 95% CI -0.08 to -0.01 s, P = 0.036, d = 0.5; Motor reaction time: -0.04 s, 95% CI -0.07 to -0.01 s, P = 0.008, d = 0.6) compared to the placebo condition. Anticipation, sustained attention, and memory were not affected after either caffeine dose intake (all P > 0.05). In addition, the 6 mg/kg dose of caffeine augmented the occurrence of the side effects of increased activeness (P = 0.046) and nervousness (P = 0.001).

CONCLUSION

Acute intake of 6 mg/kg caffeine is effective in improving reaction time despite increasing the occurrence of side effects in healthy physically active young adults.

STUDY REGISTRATION

This study has been registered in ClinicalTrials whose ID is: NCT05995314 (2023-08-08).

Caffeine Gum Improves Reaction Time but Reduces Composure Versus Placebo During the Extra-Time Period of Simulated Soccer Match-Play in Male Semiprofessional Players

This study aimed to determine whether caffeine gum influenced perceptual-cognitive and physical performance during the extra-time period of simulated soccer match-play. Semiprofessional male soccer players (n = 12, age: 22 ± 3 years, stature: 1.78 ± 0.06 m, mass: 75 ± 9 kg) performed 120-min soccer-specific exercise on two occasions. In a triple-blind, randomized, crossover design, players chewed caffeinated (200 mg; caffeine) or control (0 mg; placebo) gum for 5 min following 90 min of soccer-specific exercise. Perceptual-cognitive skills (i.e., passing accuracy, reaction time, composure, and adaptability) were assessed using a soccer-specific virtual reality simulator, collected pre- and posttrial. Neuromuscular performance (reactive-strength index, vertical jump height, absolute and relative peak power output, and negative vertical displacement) and sprint performance (15 and 30 m) were measured at pretrial, half-time, 90 min, and posttrial. Caffeine gum attenuated declines in reaction time (pre: 90.8 ± 0.8 AU to post: 90.7 ± 0.8 AU) by a further 4.2% than placebo (pre: 92.1 ± 0.8 AU to post: 88.2 ± 0.8 AU; p < .01). Caffeine gum reduced composure by 4.7% (pre: 69.1 ± 0.8 AU to post: 65.9 ± 0.8 AU) versus placebo (pre: 68.8 ± 0.8 AU to post: 68.3 ± 0.8 AU; p < .01). Caffeine gum did not influence any other variables (p > .05). Where caffeine gum is consumed by players prior to extra-time, reaction time increases but composure may be compromised, and neuromuscular and sprint performance remain unchanged. Future work should assess caffeine gum mixes with substances like L-theanine that promote a relaxed state under stressful conditions.

Evidence-based sports supplements: A redox analysis

Despite the overwhelming number of sports supplements on the market, only seven are currently recognized as effective. Biological functions are largely regulated through redox reactions, yet no comprehensive analysis of the redox properties of these supplements has been compiled. Here, we analyze the redox characteristics of these seven supplements: bicarbonates, beta-alanine, caffeine, creatine, nitrates, carbohydrates, and proteins. Our findings suggest that all sports supplements exhibit some degree of redox activity. However, the precise physiological implications of these redox properties remain unclear. Future research, employing unconventional perspectives and methodologies, will reveal new redox pixels of the exercise physiology and sports nutrition picture.

Beyond the Buzz: Do Energy Drinks Offer More Than Caffeine for Mental and Physical Tasks?

Energy drinks are marketed for enhancing mental and physical performance, often containing ingredients beyond caffeine. This study investigated whether an energy drink (ED), Gorilla Mind, exerted greater effects on sustained attention, mood, handgrip strength, and push-up performance than a caffeine-matched control drink (CAF) in exercise-trained individuals (n = 21, age: 22 ± 5.9 years). In a randomized, counterbalanced, crossover design, participants first completed tests assessing mood (Profile of Mood States; POMS), sustained attention (Psychomotor Vigilance Test; PVT), handgrip strength (HG), and 1-minute maximum push-up performance (PU). They then consumed either an ED or CAF drink (200mg caffeine) in a randomized order. After 45 minutes, the tests were repeated. Following a 1-week washout period, participants returned to consume the other drink and completed the same protocol. While the ED group improved reaction time (PVT), the Delta score between ED and CAF was not statistically significant (p = 0.3391). No significant differences were found between ED and CAF groups for other measures (POMS: p = 0.152, HG: p = 0.499, PU: p = 0.209). These findings suggest that the additional ingredients in the ED may not offer substantial benefits beyond caffeine for these measures in active individuals. It is important to note that the caffeine dose was, on average, less than 3.0 mg/kg body mass, which may have influenced the outcomes.

Pre-Exercise Caffeine and Sodium Bicarbonate: Their Effects on Isometric Mid-Thigh Pull Performance in a Crossover, Double-Blind, Placebo-Controlled Study

Caffeine and sodium bicarbonate are extensively researched ergogenic aids known for their potential to enhance exercise performance. The stimulant properties of caffeine on the central nervous system, coupled with the buffering capacity of sodium bicarbonate, have been associated with improved athletic performance. This has led to investigations of their combined effects on strength. The aim of the present study is to investigate the effect of isolated and combined caffeine and sodium bicarbonate consumption on strength using the isometric mid-thigh pull test (IMTP). Nineteen male college students (age 23.6 ± 1.6 years) participated in this crossover, double-blind, placebo-controlled study. They were exposed to the following conditions: control (no supplement), placebo (20 g maltodextrin), caffeine (6 mg/kg), sodium bicarbonate (0.3 g/kg), and a combination of caffeine and sodium bicarbonate. Supplements and placebo were diluted in water and consumed 60 min prior to the IMTP tests. Two 5 s IMTP trials were performed at 40-60% and 60-80% of One Repetition of Maximum (1RM) with a 60 s rest between. Consumption of caffeine or Caf + NaHCO3 did not significantly change peak IMTP strength values at any intensity (p = 0.110). The peak IMTP values did not show significant differences between conditions or from control condition values (1091 ± 100 N) to Caf (1224 ± 92 N), NaHCO3 (1222 ± 74 N), and Caf ± NaHCO3 (1152 ± 109 N). However, the test of the results of the ANOVA analysis of repeated measures of effect within the caffeine condition was significant for the increase in IMTP relative strength compared to control (p < 0.05). Thus, the IMTP force values increased significantly from control to Caf (p = 0.016) and from Pla to Caf (p = 0.008), but not for other comparisons (p > 0.05). In summary, caffeine supplementation alone, taken 60 min before exercise, positively affects submaximal strength performance. In contrast, sodium bicarbonate, whether taken alone or in combination with caffeine, does not enhance submaximal strength in the IMTP tests.

Exploring the relationship between caffeine metabolism-related CYP1A2 rs762551 polymorphism and team sport athlete status and training adaptations

BACKGROUND

This study aimed to achieve a dual objective: to compare the frequencies of CYP1A2 rs762551 genotypes between team sport athletes and a control group, and to determine the association between the rs762551 polymorphism and changes in physical performance after a six-week training program among elite basketball players.

METHODS

The study encompassed an analysis of 504 individuals, comprising 320 athletes and 184 controls. For the Turkish cohort, DNA was isolated using the buccal swab method, and genotyping was conducted using the KASP technique. Performance assessments included the Yo-Yo IR2 and 30 m sprint tests. For Russian participants, DNA samples were extracted from peripheral blood, a commercial kit was used for DNA extraction, and genotyping of the rs762551 polymorphism was conducted using DNA microarray.

RESULT

Notably, a statistically significant linear decline in the prevalence of the CC genotype was observed with ascending levels of athletic achievement within team sports (sub-elite: 18.0%, elite: 8.2%, highly elite: 0%; p = 0.001). Additionally, the CA genotype was the most prevalent genotype in the highly elite group compared to controls (80.0% vs. 45.1%, p = 0.048). Furthermore, statistically significant improvements in Yo-Yo IR2 performance were noted exclusively among basketball players harboring the CA genotype (p = 0.048).

CONCLUSIONS

The study's findings indicate that the rs762551 CC genotype is a disadvantage in elite team sports, whereas the CA genotype provides an advantage in basketball performance.

Effects of Different Caffeine Dosages on Maximal Physical Performance and Potential Side Effects in Low-Consumer Female Athletes: Morning vs. Evening Administration

While previous studies have explored a range of factors governing the optimal use of caffeine (CAF) in athletes, limited research has explored how time of day (TOD) affects the ergogenic effects of various CAF dosages on physical performance. This study aimed to increase knowledge about how different recommended CAF doses (3 mg/kg vs. 6 mg/kg) ingested at different TODs affected maximal high-intensity physical performance and the perception of potential side effects in female athletes. In this double-blind, randomized, and counterbalanced study, 15 low CAF consumer athletes (aged 18.3 ± 0.5 y) underwent six trials, including three testing conditions assessed across two TODs: one in the morning (08:00 a.m.) and one in the evening (06:00 p.m.). During each condition, the participants ingested either a placebo, 3 mg/kg CAF (CAF (3 mg)), or 6 mg/kg CAF (CAF (6 mg)) capsules 60 min before each test with an in-between washout period of at least 72 h. In each trial, the participants performed a countermovement jumps test (CMJ), a modified agility t test (MATT), a repeated sprint ability (RSA), a rating of perceived exertion (RPE), and finally, a CAF side effects questionnaire. Our findings indicate the absence of an ergogenic effect on CMJ, MAT, and RSA performance in the evening after administering CAF (3 mg) or CAF (6 mg) compared to a placebo. Likewise, when CAF was ingested in the morning, there was an improvement in these performances with both CAF (3 mg) and CAF (6 mg), with greater improvement observed after CAF (6 mg). Additionally, neither the CAF dosage nor the TOD had a significant effect on the RPE. The occurrence of side effects increased significantly after the evening ingestion of CAF, particularly with a moderate dose of CAF (6 mg). Our findings indicate that the effectiveness of CAF depends on the TOD and CAF dosage. When ingested in the morning, a moderate dose of CAF (6 mg), rather than CAF (3 mg), is more effective in improving short-term physical performance without affecting CAF side effects in female athletes. Nevertheless, when ingested in the evening, neither dose was sufficient to enhance short-term physical performance, and both dosages increased the incidence of CAF side effects, particularly at a moderate dose.

Total fermentable oligo-, di-, monosaccharides and polyols intake, carbohydrate malabsorption and gastrointestinal symptoms during a 56 km trail ultramarathon event

AIMS

To explore the relationship between nutritional intake, fermentable oligo-, di, monosaccharides and polyols, and carbohydrate malabsorption, with gastrointestinal symptoms during a 56 km trail ultramarathon event and identify differences in nutritional intake between runners with severe and non-severe gastrointestinal symptoms.

METHODS

Forty-four ultramarathoners recorded and self-reported dietary intake 3 days before, morning of, and during the ultramarathon with gastrointestinal symptoms obtained retrospectively and nutrient analysis via FoodWorks. Carbohydrate malabsorption was determined via breath hydrogen content pre- and post-race. Spearman's rank-order and Mann-Whitney U-tests were used to identify relationships and differences between groups.

RESULTS

Total fermentable oligo-, di, monosaccharides and polyols intake were not associated with gastrointestinal symptoms, but weak associations were observed for lower energy (rs = -0.302, p = 0.044) and fat intake (rs = -0.340, p = 0.024) 3 days before with upper gastrointestinal symptoms and higher caffeine intake 3 days before with overall gastrointestinal symptoms (rs = 0.314, p = 0.038). Total fermentable oligo-, di-, monosaccharides and polyols intake and breath hydrogen were not different between those with severe versus non-severe symptoms (p > 0.05). Although those with severe symptoms had higher caffeine (p = 0.032), and total polyols intake (p = 0.031) 3 days before, and higher % energy from fat (p = 0.043) and sorbitol intake (p = 0.026) during the race, and slower ultramarathon finish times (p = 0.042).

CONCLUSION

Total fermentable oligo-, di-, and monosaccharides intake and carbohydrate malabsorption were not associated with gastrointestinal symptoms. Additional research on the effect of fat, caffeine, and polyol intake on exercise-associated gastrointestinal symptoms is warranted and presents new nutritional areas for consideration when planning nutritional intake for ultramarathoners.

Acute effects of caffeine or quercetin ingestion on motor unit firing pattern before and after resistance exercise

The aim of the present study was to investigate the acute effect of caffeine or quercetin ingestion on motor unit firing patterns and muscle contractile properties before and after resistance exercise. High-density surface electromyography (HDs-EMG) during submaximal contractions and electrically elicited torque in knee extensor muscles were measured before (PRE) and 60 min after (POST1) ingestion of caffeine, quercetin glycosides, or placebo, and after resistance exercise (POST2) in ten young males. The Convolution Kernel Compensation technique was used to identify individual motor units of the vastus lateralis muscle for the recorded HDs-EMG. Ingestion of caffeine or quercetin induced significantly greater decreases in recruitment thresholds (RTs) from PRE to POST1 compared with placebo (placebo: 94.8 ± 9.7%, caffeine: 84.5 ± 16.2%, quercetin: 91.9 ± 36.7%), and there were significant negative correlations between the change in RTs (POST1-PRE) and RT at PRE for caffeine (rs = - 0.448, p < 0.001) and quercetin (rs =  - 0.415, p = 0.003), but not placebo (rs =  - 0.109, p = 0.440). Significant positive correlations between the change in firing rates (POST2-POST1) and RT at PRE were noted with placebo (rs = 0.380, p = 0.005) and quercetin (rs = 0.382, p = 0.007), but not caffeine (rs = 0.069, p = 0.606). No significant differences were observed in electrically elicited torque among the three conditions. These results suggest that caffeine or quercetin ingestion alters motor unit firing patterns after resistance exercise in different threshold-dependent manners in males.

Timing Matters: Time of Day Impacts the Ergogenic Effects of Caffeine-A Narrative Review

Caffeine has attracted significant attention from researchers in the sports field due to its well-documented ergogenic effects across various athletic disciplines. As research on caffeine continues to progress, there has been a growing emphasis on evaluating caffeine dosage and administration methods. However, investigations into the optimal timing of caffeine intake remain limited. Therefore, this narrative review aimed to assess the ergogenic effects of caffeine administration at different times during the morning (06:00 to 10:00) and evening (16:00 to 21:00). The review findings suggest that circadian rhythms play a substantial role in influencing sports performance, potentially contributing to a decline in morning performance. Caffeine administration has demonstrated effectiveness in mitigating this phenomenon, resulting in ergogenic effects and performance enhancement, even comparable to nighttime levels. While the specific mechanisms by which caffeine regulates circadian rhythms and influences sports performance remain unclear, this review also explores the mechanisms underlying caffeine's ergogenic effects, including the adenosine receptor blockade, increased muscle calcium release, and modulation of catecholamines. Additionally, the narrative review underscores caffeine's indirect impact on circadian rhythms by enhancing responsiveness to light-induced phase shifts. Although the precise mechanisms through which caffeine improves morning performance declines via circadian rhythm regulation necessitate further investigations, it is noteworthy that the timing of caffeine administration significantly affects its ergogenic effects during exercise. This emphasizes the importance of considering caffeine intake timing in future research endeavors to optimize its ergogenic potential and elucidate its mechanisms.

Caffeine Does Not Alter Performance, Perceptual Responses, and Oxidative Stress After Short Sprint Interval Training

Despite the abundance of research investigating the efficacy of caffeine supplementation on exercise performance, the physiological and biochemical responses to caffeine supplementation during intermittent activities are less evident. This study investigated the acute effects of caffeine supplementation on measures of exercise performance, ratings of perceived exertion, and biomarkers of oxidative stress induced by an acute bout of sprint interval training. In a randomized crossover design, 12 healthy males (age: 26 ± 4 years, height: 177.5 ± 6 cm, body mass: 80.7 ± 7.6 kg) ingested 6 mg/kg of caffeine or placebo 60 min prior to performing sprint interval training (12 × 6 s "all-out sprints" interspersed by 60 s of rest). Performance scores and ratings of perceived exertion were assessed after every sprint. Blood samples were collected before supplementation, prior to and following each sprint, and 5 and 60 min after the last sprint. Caffeine had no effect on any performance measures, ratings of perceived exertion, or biomarkers of oxidative stress (p > .05). In conclusion, caffeine supplementation does not improve performance or decrease oxidative stress after an acute bout of sprint interval training.

Timing of Caffeine Ingestion Does Not Improve Three-Point Shooting Accuracy in College Basketball Players

This study investigated the effects of the timing of caffeine (3 mg/kg body mass) ingestion on three-point shooting accuracy and other performance parameters during a basketball exercise simulation test (BEST). Eighteen college basketball players (mean ± SD: age = 24.4 ± 1.5 years, height = 181.7 ± 9.5 cm, body mass = 80.9 ± 13.2 kg) underwent one familiarization trial and three main conditions in a randomized order: (a) placebo (maltodextrin) and placebo, (b) caffeine and placebo, and (c) placebo and caffeine. Participants ingested either the placebo or caffeine pill 75 and 15 min before performing four quarters of the BEST and a three-point shooting protocol. During each quarter, participants completed 16 rounds of the BEST and ten three-point shots. Vertical jump height, 6 m sprint timing, BEST completion timing, three-point shooting accuracy, heart rate, rate of perceived exertion, blood glucose, blood lactate, and psychological measures pertaining to performance were measured. The BEST completion timing differed among conditions (placebo and placebo = 26.4 ± 2.0 s, caffeine and placebo = 25.8 ± 2.0 s, placebo and caffeine = 25.9 ± 2.1 s; p = .031) but not three-point shooting accuracy (placebo and placebo = 12.33 ± 4.10; caffeine and placebo = 12.61 ± 2.81; placebo and caffeine = 11.67 ± 3.77; p = .648), vertical jump height, or sprint times. Manipulating ingestion timing of caffeine did not improve three-point shooting accuracy, vertical jump height, or 6 m sprint timings, but caffeine can improve performance times during simulated basketball exercise irrespective of ingestion timing.

Greening up organic reactions with caffeine: applications, recent developments, and future directions

Numerous studies in the field of alkaloid chemistry have provided researchers with valuable insights into their unique properties as catalysts. Among the diverse natural catalysts, caffeine has emerged as a green, expedient, and biodegradable catalyst with high efficiency and applicability. Interest in using caffeine as a catalyst has burgeoned over the past few years with its role in diverse multicomponent reactions. Preparation of its imidazolium salts and further conversion to Nitrogen Heterocyclic Carbene (NHC) ligands and ionic liquids offers new paradigms. Caffeine has also played a multifaceted role as a support material in influencing the structural properties of nanoparticles. We hope that the chemistry of caffeine and its applications for sustainable organic transformations discussed in this review will stimulate new thinking and open new avenues in this field.

Cannabis containing THC impairs 20-min cycling time trial performance irrespective of the method of inhalation

Herein, we examine the human exercise response following cannabis inhalation, taking into consideration varied cannabinoid concentrations and different inhalation methods. A semirandomized crossover study design was used, with measures of perceived exertion and physiological responses to submaximal and maximal exercise. Participants (n = 14, 9 males 5 females) completed exercise after 1) smoking Δ-9-tetrahydrocannabinol (THC)-predominant cannabis (S-THC), 2) inhaling aerosol (vaporizing) from THC-predominant cannabis (V-THC), 3) inhaling aerosol from cannabidiol (CBD)-predominant cannabis (V-CBD), or 4) under control conditions. All exercise was performed on a cycle ergometer, with submaximal testing performed at 100 W followed by an evaluation of maximal exercise performance using an all-out 20-min time trial. Metabolism was characterized via the analysis of expired gases while subjective ratings of perceived exertion (RPE) were reported. During submaximal cycling, heart rate was higher during S-THC and V-THC compared with both control and V-CBD (all P < 0.02). During maximal exercise, V̇e was lower in V-THC compared with control, S-THC, and V-CBD (all P < 0.03), as was S-THC compared with control (P < 0.05). Both V̇o2 and RPE were similar between conditions during maximal exercise (both P > 0.1). Mean power output during the 20-min time trial was significantly lower in the S-THC and V-THC conditions compared with both control and V-CBD (all P < 0.04). Cannabis containing THC alters the physiological response to maximal and submaximal exercise, largely independent of the inhalation method. THC-containing cannabis negatively impacts vigorous exercise performance during a sustained 20-min effort, likely due to physiological and psychotropic effects. Inhalation of cannabis devoid of THC and primarily containing CBD has little physiological effect on the exercise response or performance.NEW & NOTEWORTHY Inhalation of cannabis containing THC alters physiological responses to both submaximal and maximal exercise and reduces mean power output during a 20-min time trial, regardless of whether it is inhaled as smoke or aerosol. In contrast, cannabis devoid of THC and predominantly containing CBD has no effect on physiological responses to exercise or performance.

Optimizing Short-Term Maximal Exercise Performance: The Superior Efficacy of a 6 mg/kg Caffeine Dose over 3 or 9 mg/kg in Young Female Team-Sports Athletes

Caffeine (CAF) is among the most extensively researched dietary supplements worldwide. However, little is known about the relationship between dosage and performance enhancement, particularly in female athletes. This study aimed to explore the effects of three different CAF dosages (3 mg·kg-1, 6 mg·kg-1, and 9 mg·kg-1) on high-intensity exercise and the prevalence of undesirable side effects related to these doses among female team-sports athletes. All participants (n = 16; age: 16.9 ± 0.6 y; height: 1.64 ± 0.1 m; BMI: 21.6 ± 1.5 kg·m-2) were mild CAF consumers. This study had a randomized, crossover, double-blind design in which each athlete performed four experimental sessions after ingesting either a placebo (PLAC), 3 mg·kg-1 CAF (CAF-3), 6 mg·kg-1 CAF (CAF-6), or 9 mg·kg-1 of CAF (CAF-9), with an in-between washout period of at least 72 h. In each experimental session, 60 min after ingesting the capsules, participants underwent a countermovement jumps test (CMJ), modified agility t-test (MATT), repeated sprint ability (RSA) test, and a rating of perceived exertion (RPE) and completed the CAF side effects questionnaire. Our findings revealed that in comparison to the PLAC condition, the MATT, RSAmean, and RSAbest performances were significantly greater only under the CAF-6 and CAF-9 conditions. Although the RPE scores remained unchanged, CMJ performance improved under all CAF conditions. All the performance outcomes were better for the CAF-6 and CAF-9 conditions than for the CAF-3 condition. Notably, no significant difference between the CAF-6 and CAF-9 conditions was observed for any of these parameters despite the highest incidence of side effects being noted for the CAF-9 condition. In summary, our findings highlight the recommendation for a moderate CAF dosage of 6 mg·kg-1 rather than 3 or 9 mg·kg-1 to enhance various aspects of short-term maximal performance in mild-CAF-consumer female team-sports athletes while mitigating the occurrence of adverse CAF side effects.

The protective effect of caffeine against oxalate-induced epithelial-mesenchymal transition in renal tubular cells via mitochondrial preservation

Mitochondrial dysfunction is one of the key mechanisms for developing chronic kidney disease (CKD). Hyperoxaluria and nephrolithiasis are also associated with mitochondrial dysfunction. Increasing evidence has shown that caffeine, the main bioactive compound in coffee, exerts both anti-fibrotic and anti-lithogenic properties but with unclear mechanisms. Herein, we address the protective effect of caffeine against mitochondrial dysfunction during oxalate-induced epithelial-mesenchymal transition (EMT) in renal cells. Analyses revealed that oxalate successfully induced EMT in MDCK renal cells as evidenced by the increased expression of several EMT-related genes (i.e., Snai1, Fn1 and Acta2). Oxalate also suppressed cellular metabolic activity and intracellular ATP level, but increased reactive oxygen species (ROS). Additionally, oxalate reduced abundance of active mitochondria and induced mitochondrial fragmentation (fission). Furthermore, oxalate decreased mitochondrial biogenesis and content as evidenced by decreased expression of sirtuin-1 (SIRT1), peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), cytochrome c oxidase subunit 4 (COX4), and total mitochondrial proteins. Nonetheless, these oxalate-induced deteriorations in MDCK cells and their mitochondria were successfully hampered by caffeine. Knockdown of Snai1 gene by small interfering RNA (siRNA) completely abolished the effects of oxalate on suppression of cellular metabolic activity, intracellular ATP and abundance of active mitochondria, indicating that these oxalate-induced renal cell deteriorations were mediated through the Snai1 EMT-related gene. These data, at least in part, unveil the anti-fibrotic mechanism of caffeine during oxalate-induced EMT in renal cells by preserving mitochondrial biogenesis and function.

Effect of Acute Caffeine Intake on Fat Oxidation Rate during Fed-State Exercise: A Systematic Review and Meta-Analysis

Pre-exercise intake of caffeine (from ~3 to 9 mg/kg) has been demonstrated as an effective supplementation strategy to increase fat oxidation during fasted exercise. However, a pre-exercise meal can alter the potential effect of caffeine on fat oxidation during exercise as caffeine modifies postprandial glycaemic and insulinemic responses. Hypothetically, the effect of caffeine on fat oxidation may be reduced or even withdrawn during fed-state exercise. The present systematic review aimed to meta-analyse investigations on the effect of acute caffeine intake on the rate of fat oxidation during submaximal aerobic exercise performed in the fed state (last meal < 5 h before exercise). A total of 18 crossover trials with randomised and placebo-controlled protocols and published between 1982 and 2021 were included, with a total of 228 participants (185 males and 43 females). Data were extracted to compare rates of fat oxidation during exercise with placebo and caffeine at the same exercise intensity, which reported 20 placebo-caffeine pairwise comparisons. A meta-analysis of the studies was performed, using the standardised mean difference (SMD) estimated from Hedges' g, with 95% confidence intervals (CI). In comparison with the placebo, caffeine increased the rate of fat oxidation during fed-state exercise (number of comparisons (n) = 20; p = 0.020, SMD = 0.65, 95% CI = 0.20 to 1.20). Only studies with a dose < 6 mg/kg of caffeine (n = 13) increased the rate of fat oxidation during fed-state exercise (p = 0.004, SMD = 0.86, 95% CI = 0.27 to 1.45), while no such effect was observed in studies with doses ≥6 mg/kg (n = 7; p = 0.97, SMD = -0.03, 95% CI = -1.40 to 1.35). The effect of caffeine on fat oxidation during fed-state exercise was observed in active untrained individuals (n = 13; p < 0.001, SMD = 0.84, 95% CI = 0.39 to 1.30) but not in aerobically trained participants (n = 7; p = 0.27, SMD = 0.50, 95% CI = -0.39 to 1.39). Likewise, the effect of caffeine on fat oxidation was observed in caffeine-naïve participants (n = 9; p < 0.001, SMD = 0.82, 95% CI = 0.45 to 1.19) but not in caffeine consumers (n = 3; p = 0.54, SMD = 0.57, 95% CI = -1.23 to 2.37). In conclusion, acute caffeine intake in combination with a meal ingested within 5 h before the onset of exercise increased the rate of fat oxidation during submaximal aerobic exercise. The magnitude of the effect of caffeine on fat oxidation during fed-state exercise may be modulated by the dose of caffeine administered (higher with <6 mg/kg than with ≥6 mg/kg), participants' aerobic fitness level (higher in active than in aerobically trained individuals), and habituation to caffeine (higher in caffeine-naïve than in caffeine consumers).

Use of Resonant Acoustic Mixing Technology for Ultra-Low-Dose Blending in a Single-Step Mixing Process

PURPOSE

To evaluate the use of resonant acoustic mixing (RAM) technology for homogenous blending of a morphologically challenging model API in low-dose concentrations (<0.1% w/w), and assess the potential for blend uniformity (BU) optimization.

METHODS

Caffeine (CAF) mixing was carried out using a LabRAM I benchtop mixer. Uniformity was assessed under a range of mixing conditions and sample preparation procedures in order to optimize system performance. The capacity for microscale mixing was evaluated from final parameters for 0.05% and 0.0125% CAF blends.

RESULTS

Upon optimization, RAM was able to accurately prepare homogeneous mixtures of <0.1% CAF in dilutions of up to 1 part per 8,000. Results from a 0.05% blend targeting 125 μg CAF dosage amounts revealed an AV score of 8.8 while a 0.0125% w/w blend accurately prepared 25 μg of CAF with 99.3% accuracy (98.7% label claim) and AV of 10.1. Microscale mixing in the 0.05% w/w blend was confirmed from plots of BU data against sample size demonstrating a slope of 0.05 within the range of 250-10 mg sample (125-5 μg CAF). L1 BU criteria only failed at the level of 2 μg CAF, despite target precision to 26 nanograms (98.7% label claim).

CONCLUSIONS

This study presents the first instance of a homogenously mixed <0.1% (w/w) blend using RAM technology and demonstrate the suitability for reproducible dosing of single-digit microgram drug amounts. Uniformity is documented for API amounts 60x smaller than a recent report has shown and 10,000x smaller than achieved previously with CAF.

Caffeine causes cell cycle arrest at G0/G1 and increases of ubiquitinated proteins, ATP and mitochondrial membrane potential in renal cells

Caffeine is a well-known purine alkaloid commonly found in coffee. Several lines of previous and recent evidence have shown that habitual coffee drinking is associated with lower risks for chronic kidney disease (CKD) and nephrolithiasis. However, cellular and molecular mechanisms underlying its renoprotective effects remain largely unknown due to a lack of knowledge on cellular adaptive response to caffeine. This study investigated cellular adaptive response of renal tubular cells to caffeine at the protein level. Cellular proteome of MDCK cells treated with caffeine at a physiologic concentration (100 μM) for 24 h was analyzed comparing with that of untreated cells by label-free quantitative proteomics. From a total of 936 proteins identified, comparative analysis revealed significant changes in levels of 148 proteins induced by caffeine. These significantly altered proteins were involved mainly in proteasome, ribosome, tricarboxylic acid (TCA) (or Krebs) cycle, DNA replication, spliceosome, biosynthesis of amino acid, carbon metabolism, nucleocytoplasmic transport, cell cycle, cytoplasmic translation, translation initiation, and mRNA metabolic process. Functional validation by various assays confirmed that caffeine decreased cell population at G2/M, increased cell population at G0/G1, increased level of ubiquitinated proteins, increased intracellular ATP and enhanced mitochondrial membrane potential in MDCK cells. These data may help unravelling molecular mechanisms underlying the biological effects of caffeine on renal tubular cells at cellular and protein levels.

Does Caffeine Increase Fat Metabolism? A Systematic Review and Meta-Analysis

Whether caffeine (CAF) increases fat metabolism remains debatable. Using systematic review coupled with meta-analysis, our aim was to determine effects of CAF on fat metabolism and the relevant factors moderating this effect. Electronic databases PubMed, SPORTDiscus, and Web of Science were searched using the following string: CAF AND (fat OR lipid) AND (metabolism OR oxidation). A meta-analytic approach aggregated data from 94 studies examining CAF's effect on fat metabolism assessed by different biomarkers. The overall effect size (ES) was 0.39 (95% confidence interval [CI] [0.30, 0.47], p < .001), indicating a small effect of CAF to increase fat metabolism; however, ES was significantly higher (p < .001) based on blood biomarkers (e.g., free fatty acids, glycerol) (ES = 0.55, 95% CI [0.43, 0.67]) versus expired gas analysis (respiratory exchange ratio, calculated fat oxidation) (ES = 0.26, 95% CI [0.16, 0.37]), although both were greater than zero. Fat metabolism increased to a greater extent (p = .02) during rest (ES = 0.51, 95% CI [0.41, 0.62]) versus exercise (ES = 0.35, 95% CI [0.26, 0.44]) across all studies, although ES was not different for studies reporting both conditions (ES = 0.49 and 0.44, respectively). There were no subgroup differences based on participants' fitness level, sex, or CAF dosage. CAF ingestion increases fat metabolism but is more consistent with blood biomarkers versus whole-body gas exchange measures. CAF has a small effect during rest across all studies, although similar to exercise when compared within the same study. CAF dosage did not moderate this effect.

Anti-Inflammatory Effect of Caffeine on Muscle under Lipopolysaccharide-Induced Inflammation

Evidence has shown that caffeine administration reduces pro-inflammatory biomarkers, delaying fatigue and improving endurance performance. This study examined the effects of caffeine administration on the expression of inflammatory-, adenosine receptor- (the targets of caffeine), epigenetic-, and oxidative metabolism-linked genes in the vastus lateralis muscle of mice submitted to lipopolysaccharide (LPS)-induced inflammation. We showed that caffeine pre-treatment before LPS administration reduced the expression of Il1b, Il6, and Tnfa, and increased Il10 and Il13. The negative modulation of the inflammatory response induced by caffeine involved the reduction of inflammasome components, Asc and Casp1, promoting an anti-inflammatory scenario. Caffeine treatment per se promoted the upregulation of adenosinergic receptors, Adora1 and Adora2A, an effect that was counterbalanced by LPS. Moreover, there was observed a marked Adora2A promoter hypermethylation, which could represent a compensatory response towards the increased Adora2A expression. Though caffeine administration did not alter DNA methylation patterns, the expression of DNA demethylating enzymes, Tet1 and Tet2, was increased in mice receiving Caffeine+LPS, when compared with the basal condition. Finally, caffeine administration attenuated the LPS-induced catabolic state, by rescuing basal levels of Ampk expression. Altogether, the anti-inflammatory effects of caffeine in the muscle can be mediated by modifications on the epigenetic landscape.

Effect of caffeine intake on fat oxidation rate during exercise: is there a dose-response effect?

PURPOSE

The effect of caffeine to enhance fat utilisation as fuel for submaximal aerobic exercise is well established. However, it is unknown whether this effect is dose dependent. The aim of this study was to investigate the effect of 3 and 6 mg of caffeine per kg of body mass (mg/kg) on whole-body substrate oxidation during an incremental cycling exercise test.

METHODS

In a double-blind, randomised, and counterbalanced experiment, 18 recreationally active males (maximal oxygen uptake [VO_2max] = 56.7 ± 8.2 mL/kg/min) performed three experimental trials after ingesting either 3 mg/kg of caffeine, 6 mg/kg of caffeine or a placebo (cellulose). The trials consisted of an incremental exercise test on a cycle ergometer with 3-min stages at workloads from 30 to 80% of VO_2max. Energy expenditure, fat oxidation rate, and carbohydrate oxidation rate were continuously measured by indirect calorimetry.

RESULTS

During exercise, there was significant effect of substance (F = 7.969; P = 0.004) on fat oxidation rate. In comparison to the placebo, the rate of fat oxidation was higher with 3 mg/kg of caffeine at 30, 40, 50 and 70% of VO_2max [all P < 0.050, effect sizes (ES) from 0.38 to 0.50] and with 6 mg/kg of caffeine at 30, 40, 50, 60 and 70% of VO_2max (all P < 0.050, ES from 0.28 to 0.76). Both 3 mg/kg (0.40 ± 0.21 g/min, P = 0.021, ES = 0.57) and 6 mg/kg of caffeine (0.40 ± 0.17 g/min P = 0.001, ES = 0.60) increased the maximal rate of fat oxidation during exercise over the placebo (0.31 ± 0.15 g/min). None of the caffeine doses produced any significant effect on energy expenditure or heart rate during exercise, while both caffeine doses reduced perceived fatigue at 80% of VO_2max (all P < 0.050, ES from 0.71 to 1.48).

CONCLUSION

The effect of caffeine to enhance fat oxidation during submaximal aerobic exercise is of similar magnitude with 3 and 6 mg of caffeine per kg of body mass. Thus, a dose of 3 mg of caffeine per kg of body mass would be sufficient to enhance fat utilisation as fuel during submaximal exercise.

Quantitative proteomics reveals common and unique molecular mechanisms underlying beneficial effects of caffeine and trigonelline on human hepatocytes

Caffeine and trigonelline are the major bioactive compounds in coffee. Caffeine alone or combined with other coffee compounds shows hepatoprotective effects. However, molecular mechanisms underlying such hepatoprotective effects remain unclear. We therefore addressed molecular effects of caffeine and trigonelline on human hepatocytes using quantitative proteomics followed by bioinformatic analyses to obtain topological and functional significance. HepG2 cells were treated with 100 μM caffeine or trigonelline for 24-h and evaluated by quantitative proteomics using nanoLC-ESI-LTQ-Orbitrap MS/MS. A total of 26 and 25 significantly altered proteins were identified in caffeine-treated and trigonelline-treated cells, respectively, compared with control cells. Topological analyses revealed that ribosomal and translation regulatory proteins predominantly served as the hub proteins associated with protein clusters. Functional analyses also revealed that these two bioactive compounds shared some molecular mechanisms via induction of translational processes. There were also other unique molecular functions and biological processes triggered or suppressed by either caffeine or trigonelline. These data highlight common and unique molecular mechanisms underlying the hepatoprotective effects of caffeine and trigonelline that may be useful for future clinical applications.

Exogenous Caffeine Ingestion Does Not Increase Plantarflexor Torque in Older or Younger Men

Aging is associated with neurodegeneration and a loss of muscle function, especially in lower-limb muscles. While caffeine may augment muscle force generation through multiple effects on the central nervous system, no studies have yet compared the effects of caffeine on force-generating capacity between younger and older men, who might respond differently due to age-related changes in the structures on which caffeine acts. In a double-blind, controlled trial, 22 younger (25 ± 5 years) and 21 older (68 ± 6 years) men were tested for isometric plantarflexor torque on two separate days (2-7 days apart) before and 60 min after ingesting 3 mg/kg (∼2 cups of coffee) of caffeine or placebo. No effects of caffeine ingestion on peak torque or rate of torque development were detected in either older or younger men. Therefore, 3 mg/kg of caffeine may not acutely counteract age-related decreases in force capacity of the functionally important plantarflexor muscles.

The Effect of Caffeinated Chewing Gum on Volleyball-Specific Skills and Physical Performance in Volleyball Players

No previous study analyzed the effect of caffeinated chewing gum on volleyball-specific skills and physical performance in volleyball players. Twelve volleyball players participated ina randomized, crossover, and double-blind experiment after ingestion of (a) ~3.2 ± 0.4 mg/kg of body mass (BM) of caffeine via chewing gum or (b) non-caffeinated chewing gum (placebo) and performed: (a) a countermovement jump, (b) a squat jump, (c), an attack jump, (d) a block jump, (e) 5 and 10 m sprints, (f) a modified agility t-test, (g) an attack and service speed test, and (h) a spike and serve accuracy test. Compared to the placebo, the caffeine chewing gum supplementation significantly improved the accuracy of the attack (15 ± 4 vs. 18 ± 3 points, p = 0.02). However, the ingestion of caffeinated chewing gum had no effect on the remaining other performance tests (p from 0.12 to 1.00). A caffeine-containing chewing gum with a dose of ~3 mg/kg BM effectively improved the attack's accuracy in volleyball players. However, this effect was not observed in better results in jumping, running, and other skill-based volleyball tests.

Mental Performance and Sport: Caffeine and Co-consumed Bioactive Ingredients

The plant defence compound caffeine is widely consumed as a performance enhancer in a sporting context, with potential benefits expected in both physiological and psychological terms. However, although caffeine modestly but consistently improves alertness and fatigue, its effects on mental performance are largely restricted to improved attention or concentration. It has no consistent effect within other cognitive domains that are important to sporting performance, including working memory, executive function and long-term memory. Although caffeine's central nervous system effects are often attributed to blockade of the receptors for the inhibitory neuromodulator adenosine, it also inhibits a number of enzymes involved both in neurotransmission and in cellular homeostasis and signal propagation. Furthermore, it modulates the pharmacokinetics of other endogenous and exogenous bioactive molecules, in part via interactions with shared cytochrome P450 enzymes. Caffeine therefore enjoys interactive relationships with a wide range of bioactive medicinal and dietary compounds, potentially broadening, increasing, decreasing, or modulating the time course of their functional effects, or vice versa. This narrative review explores the mechanisms of action and efficacy of caffeine and the potential for combinations of caffeine and other dietary compounds to exert psychological effects in excess of those expected following caffeine alone. The review focusses on, and indeed restricted its untargeted search to, the most commonly consumed sources of caffeine: products derived from caffeine-synthesising plants that give us tea (Camellia sinensis), coffee (Coffea genus), cocoa (Theabroma cacao) and guaraná (Paullinia cupana), plus multi-component energy drinks and shots. This literature suggests relevant benefits to mental performance that exceed those associated with caffeine for multi-ingredient energy drinks/shots and several low-caffeine extracts, including high-flavanol cocoa and guarana. However, there is a general lack of research conducted in such a way as to disentangle the relative contributions of the component parts of these products.

Risk or benefit? Side effects of caffeine supplementation in sport: a systematic review

PURPOSE

The aim of this study was to systematically review evidence on the prevalence and magnitude of side effects associated with caffeine supplementation in athletes.

METHODS

Systematic searches through the PubMed, VHL, Scopus, and Web of Science databases were conducted according to the PRISMA guidelines. Peer-reviewed articles written in English that reported the prevalence/percentage or magnitude/effect size of side effects after caffeine supplementation in athletes in a sports context were included. Studies were grouped by the dose of caffeine administered as follows: low =  ≤ 3.0 mg/kg; moderate = from 3.1 to 6.0 mg/kg; high =  ≥ 6.1 mg/kg. The magnitude of the side effects was calculated with effect sizes.

RESULTS

The search retrieved 25 studies that met the inclusion/exclusion criteria with a pooled sample of 421 participants. The supplementation with caffeine produced a higher prevalence or magnitude of all side effects under investigation when compared to placebo/control situations. The prevalence (magnitude) was between 6 and 34% (ES between 0.13 and 1.11) for low doses of caffeine, between 0 and 34% (ES between -0.13 and 1.20) for moderate doses of caffeine, and between 8 and 83% (ES between 0.04 and 1.52) with high doses of caffeine. The presence of tachycardia/heart palpitations and the negative effects on sleep onset had the highest prevalence and magnitude, in athletes using supplementation with caffeine.

CONCLUSION

In summary, caffeine supplementation in the doses habitually used to enhance physical performance produces several side effects, both after exercise and at least 24 h after the ingestion. However, the prevalence and magnitude of side effects with high doses of caffeine were habitually higher than with low doses of caffeine. From a practical perspective, using ~3.0 mg/kg of caffeine may be the dose of choice to obtain the ergogenic benefits of caffeine with the lowest prevalence and magnitude of side effects.

Low and Moderate Doses of Caffeinated Coffee Improve Repeated Sprint Performance in Female Team Sport Athletes

The aim of this study was to determine the effect of low and moderate doses of caffeine ingestion via caffeinated coffee on repeated sprint test (RST) and plasma catecholamine concentration in trained female team-sport athletes. In a randomized, double-blind, crossover design, 13 female team-sport athletes (VO2max: 48.7 ± 4 mL·kg·min−1) completed three RST trials, separated by 4-day, 60 min post-ingestion of either 3 mg·kg−1 (LCOF) or 6 mg·kg−1 (MCOF) or placebo (PLA). The RST consisted of 12 × 4 s sprints on a cycle ergometer interspersed with 20 s of active recovery. Blood lactate (BLa) and glucose (GLU) and epinephrine and norepinephrine concentrations were collected before and 60 min after coffee ingestion, and after RST. Heart rate (HR) and ratings of perceived exertion (RPE) were measured at the beginning of RST, and after the 6th and 12th sprints. Average peak power score during RST was significantly improved after LCOF (p = 0.016) and MCOF (p = 0.041) compared to PLA, but peak and mean power output of the individual sprints, and fatigue index were not different between trials (all p > 0.05). Epinephrine and norepinephrine concentrations were significantly higher before and after RST in LCOF and MCOF compared to PLA (all p < 0.05). BLa was also higher after RST in both LCOF and MCOF compared to PLA (p = 0.005). HR, RPE, and GLU were not different between conditions (p > 0.05). In conclusion, low and moderate dose of caffeine ingestion can enhance the average peak power score during repeated sprints. These findings partly support low and moderate doses of caffeine supplementation via coffee as a nutritional ergogenic aid for trained female team-sport players during repeated sprint exercise.

A low- dose of caffeine suppresses EEG alpha power and improves working memory in healthy University males

The effects of a low dose of caffeine, administered in the morning, on brain wave activity and cognitive function were investigated in 25 healthy university Southeast Asian men (mean age ±standard deviation: 21 ± 2 years). Participants received a placebo (PLA) or a 50 mg caffeinated drink (CAF) under randomized, double-blind crossover conditions, with 1 week between conditions. Brain wave activity was assessed using electroencephalography (EEG) from a 5 min eyes-closed resting state. Cognitive function, i.e., visuomotor processing speed, working memory, and attention were assessed using the trail-making test A (Trails A) and B (Trails B), and digit span Forwards (DF), respectively. All tests were examined before drinking (BD), 30 min after drinking (AD), and 35 min after 5-min isokinetic exercise (AE). [Results] The CAF showed a significant decrease in the percentage changes from baseline (%∆) of alpha wave activity over the midline electrodes, i.e., frontal, central, and occipital areas after AD (p<0.05). Data from cognitive function tests were significantly improved after AD (p<0.05). A significant inverse correlation between the diminished alpha wave activity over the midline central and occipital cortical regions and the Trails B positive scores were observed (p<0.05). [Conclusion] The diminishment in resting alpha wave activity and improvement of cognitive function on working memory assessed by the Trails B following caffeine consumption would support the stimulant effects of low-dose caffeine as a morning wake-up drink in young adults.

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.

The influence of blue light on sleep, performance and wellbeing in young adults: A systematic review

Introduction: Blue light from electronic devices has a bad reputation. It has a wavelength which may influence our circadian rhythm and cause bad sleep. But there are other aspects of blue light exposure which are often overlooked, for example, it may influence performance and wellbeing. However, few resources summarize its effects systematically. Therefore, the goal of this systematic review was to distil the present evidence on blue light exposure and its influence on sleep, performance and wellbeing and discuss its significance for athletes.

Methods: The databases that were searched were Cochrane, Embase, Pubmed, Scopus, and Virtual Health Library. The studies included investigated the influence of blue light exposure on either sleep, performance, wellbeing or a combination of those parameters on healthy humans. Quality assessment was done based on the quantitative assessment tool “QualSyst.”

Results: Summarizing the influence of blue light exposure, the following results were found (expressed as proportion to the number of studies investigating the particular parameter): Fifty percent of studies found tiredness to be decreased. One fifth of studies found sleep quality to be decreased and one third found sleep duration to be decreased. Half of the studies found sleep efficacy to be decreased and slightly less than half found sleep latency to be increased. More than one half of the studies found cognitive performance to be increased. Slightly more than two thirds found alertness to be increased and reaction time to be decreased. Slightly less than half of the studies found wellbeing to be increased.

Conclusion: Blue light exposure can positively affect cognitive performance, alertness, and reaction time. This might benefit sports reliant on team-work and decision-making and may help prevent injury. Blue light might also have negative effects such as the decrease in sleep quality and sleep duration, which might worsen an athlete’s physical and cognitive performance and recovery. Further research should explore if blue light can improve sleep, performance and wellbeing to significantly benefit athletic performance.

Acute Supplementation with Capsaicin Enhances Upper-Limb Performance in Male Jiu-Jitsu Athletes

The present study investigated whether acute capsaicin (CAP) supplementation improves mean power output (MPO) and peak velocity (PV) during the performance of the free bench press exercise (FBP). Twelve (n = 12) male Brazilian Jiu-Jitsu (BJJ) athletes (age: 24.3 ± 1.5 years, height: 1.74 ± 0.1 m, body mass: 75.7 ± 10.1 kg) participated in this randomized, placebo (PLA)-controlled, double-blind, crossover trial. For each condition, 45 min after CAP (12 mg purified) or PLA (12 mg of Celulomax E) consumption, the participants performed four sets of five repetitions of FBP at a load of 60% of body mass with five-min rest intervals. The MPO (t = 5.6, df = 11, p = 0.001, EF = 0.3, IC 95% = −0.55 to 1.05) and PV (t = 5.4, df = 11, p = 0.001, EF = 0.5, IC 95% = −0.32 to 1.30) were significantly higher with CAP supplementation versus PLA. Acute CAP supplementation appears to improve MPO and PV during FBP in male BJJ athletes.

Analysis of Sport Supplement Consumption by Competitive Swimmers According to Sex and Competitive Level

Sports supplements (SS) are commonly used by athletes to improve their performance. SS use by competitive swimmers is reported to be prevalent but there is no evidence of such use by elite swimmers, either male or female. The objective of this research was to study the patterns of SS use by competitive swimmers based on sex and competitive levels (national and international); Methods: Using the categories of the Australian Institute of Sport (AIS), a total of 102 competitive swimmers (59 men and 43 women) completed a validated self-administered questionnaire on the use of SS; (3) Results: Overall, 86.9% of swimmers had consumed SSs with no differences observed between males and females (p = 0.247) or between competitive levels (p = 0.597). The SS that were most consumed by swimmers were caffeine (53.5%), sport drinks (52.5%), sport bars (51.5%), and vitamin C (43.4%). SSs categorized as medical supplements were consumed significantly more frequently by international swimmers (p = 0.012), with significant differences also found in the level—sex interaction (p = 0.049); (4) Conclusions: Compared to other sports disciplines, the prevalence of SS consumption is high in competitive swimmers regardless of performance level or gender. However, the consumption of medical supplements was greater in swimmers at a higher performance level.

Acute Effects of Caffeine Supplementation on Physical Performance, Physiological Responses, Perceived Exertion, and Technical-Tactical Skills in Combat Sports: A Systematic Review and Meta-Analysis

Although the effects of caffeine supplementation on combat sports performance have been extensively investigated, there is currently no consensus regarding its ergogenic benefits.This systematic review with meta-analysis aimed to summarize the studies investigating the effects of caffeine supplementation on different aspects of performance in combat sports and to quantitatively analyze the results of these studies to better understand the ergogenic effect of caffeine on combat sports outcomes. A systematic search for randomized placebo-controlled studies investigating the effects of caffeine supplementation on combat sports' performance was performed through Scopus, Pubmed, Web of Science and Cochrane Library databases up to 18 April 2022. Random-effects meta-analyses of standardized mean differences (Hedge's g) were performed to analyze the data. Twenty-six studies of good and excellent methodological quality (based on the Pedro scale) fulfilled the inclusion criteria. The meta-analysis results revealed caffeine has a small but evident effect size (ES) on handgrip strength (ES = 0.28; 95% CI: 0.04 to 0.52; p = 0.02), and total number of throws during the special judo fitness test (SJFT) (ES = 0.42; 95% CI: 0.06 to 0.78; p = 0.02). Regarding the physiological responses, caffeine increased blood lactate concentration ([La]) in anaerobic exercise (ES = 1.23; 95% CI: 0.29 to 2.18; p = 0.01) and simulated combat (ES = 0.91; 95% CI: 0.34 to 1.47; p = 0.002). For Heart Rate (HR), caffeine increased HR final (ES = 0.31; 95% CI: 0.11 to 0.52; p = 0.003), and HR 1min (ES = 0.20; 95% CI 0.004 to 0.40; p = 0.045). However, caffeine had no impact on the countermovement jump height, the SJFT index, the judogi strength-endurance test, the number and duration of offensive actions, HR at the end of the fight, and the rating of perceived exertion. Caffeine supplementation may be ergogenic for a range of combat sports aspects involving isometric strength, anaerobic power, reaction time, and anaerobic metabolism. However, supplementation effects might be ineffective under certain circumstances, indicating supplementation needs to take into account the performance metric in question prior to creating a dosing protocol.

Clinical Effect of Electroacupuncture on Acute Sleep Deprivation and Event-Related Potential Affecting the Inhibition Control of the Brain: Study Protocol for a Randomized Controlled Trial

Background

Acute sleep deprivation (ASD) can effect mood, attention, memory, alertness and metabolism. Especially, it is often accompanied by cognitive impairment of the brain. Acupuncture is safe and effective for improving cognitive function, but its underlying mechanism is not fully understood. In this study, an event-related potential (ERP) technique will be employed to measure the behavioral, cognitive, and physiological changes produced by electroacupuncture intervention after ASD.

Methods

We will recruit 60 healthy subjects. The participants will be randomly divided into a treatment group, a control group, a sham electroacupuncture group and a blank group, at a 1:1:1:1 ratio. The primary outcome will be determined by the change from baseline to 36 h in the MoCA score. The secondary results include the amplitude and latency of ERP N2 and P3, Go-hit rates, Go-RTs, No-Go-FA rates, the WCST, the Digit Span Subtest of the WAIS, the ESS score and FS-14. The 15 healthy subjects will not receive acupuncture treatment and ASD, but will receive EEG records and cognition functions test at the beginning and end of the experiment. Electroacupuncture intervention will be performed for 30 min once every 12 h, a total of three times. ERP measurements and other tests will be performed after baseline and ASD, and the statistician and outcome evaluator will be blinded to treatment allocation.

Discussion

This study is expected to investigate the effectiveness of electroacupuncture in improving cognition for ASD.

Trial Registration

ChiCTR2200055999.

Effect of Pre-Exercise Caffeine Intake on Endurance Performance and Core Temperature Regulation During Exercise in the Heat: A Systematic Review with Meta-Analysis

BACKGROUND

Heat is associated with physiological strain and endurance performance (EP) impairments. Studies have investigated the impact of caffeine intake upon EP and core temperature (C_T) in the heat, but results are conflicting. There is a need to systematically determine the impact of pre-exercise caffeine intake in the heat.

OBJECTIVE

To use a meta-analytical approach to determine the effect of pre-exercise caffeine intake on EP and C_T in the heat.

DESIGN

Systematic review with meta-analysis.

DATA SOURCES

Four databases and cross-referencing.

DATA ANALYSIS

Weighted mean effect summaries using robust variance random-effects models for EP and C_T, as well as robust variance meta-regressions to explore confounders.

STUDY SELECTION

Placebo-controlled, randomized studies in adults (≥ 18 years old) with caffeine intake at least 30 min before endurance exercise ≥ 30 min, performed in ambient conditions ≥ 27 °C.

RESULTS

Respectively six and 12 studies examined caffeine's impact on EP and C_T, representing 52 and 205 endurance-trained individuals. On average, 6 mg/kg body mass of caffeine were taken 1 h before exercises of ~ 70 min conducted at 34 °C and 47% relative humidity. Caffeine supplementation non-significantly improved EP by 2.1 ± 0.8% (95% CI - 0.7 to 4.8) and significantly increased the rate of change in C_T by 0.10 ± 0.03 °C/h (95% CI 0.02 to 0.19), compared with the ingestion of a placebo.

CONCLUSION

Caffeine ingestion of 6 mg/kg body mass ~ 1 h before exercise in the heat may provide a worthwhile improvement in EP, is unlikely to be deleterious to EP, and trivially increases the rate of change in C_T.

Caffeine intake and its influences on heart rate variability recovery in healthy active adults after exercise: A systematic review and meta-analysis

AIMS

Results regarding the effects of caffeine (CAF) intake on the autonomic control of heart rate recovery exercise remain inconclusive. Thus far, no study has used effect measures to pool the results of different experiments. We aim to assess the acute effect of CAF intake before exercise on the recovery of heart rate variability (HRV) after exercise through a systematic review and meta-analysis.

DATA SYNTHESIS

Randomized controlled clinical trials were included; sample composed of physically active or trained adults; CAF should be offered/ingested before exercise, with dosage between 100 and 400 mg or between 2 and 6 mg/kg and administration/ingestion route analogous in the protocols; studies required to present results of HRV indices before and after exercise. Bias risk analysis and meta-analysis were performed. Twelve studies were included in the qualitative synthesis and five studies were encompassed in the quantitative synthesis (meta-analysis). For the Root-mean-square standard deviation (RMSSD) index we revealed p = 0.67, Total 95% confidence interval (95% CI) ranged from -0.45 to 0.29, and 66.7% for heterogeneity between groups were reported. Concerning the High Frequency (HF) index, we observed p = 0.22, Total 95% CI that ranged from -0.34 to 0.30, and 44% for heterogeneity between groups.

CONCLUSIONS

CAF intake did not affect heart rate variability recovery after exercise.

A Systematic Review of the Effects of Caffeine on Basketball Performance Outcomes

Simple Summary

Caffeine is a stimulant of the central nervous system widely utilized by many athletes to enhance endurance, strength, and power-based sports performances. Whether ergogenic enhancements following caffeine ingestion result in improvements in sports-specific skills performance has received less attention. In basketball, the ability to execute certain tasks with accuracy, such as shooting and passing, are key factors affecting the outcome of the sport. Besides being able to excel in accuracy-based tasks, the possession of strong physical attributes, including vertical jump height, sprint speed and agility, are also key components to basketball performance. In this review, an overview of the effects of caffeine on basketball-related skill tasks and physical aspects of performance deemed important for the game is provided. One of the key focal points is that the efficacy of caffeine is influenced by a multitude of determinants that have an overall impact on the ergogenic capacity of caffeine. Proper awareness of these determinants allows basketball players, coaches, and trainers to have better insights and knowledge in applying caffeine to improve basketball-related performances.

Abstract

Caffeine is an ergogenic aid in many sports, including basketball. This systematic review examines the effects of caffeine on basketball-related skill tasks along with physical aspects of performance deemed important for the game. A systematic search was conducted across three databases (PubMed, SPORTDiscus and Web of Science) to identify randomized-controlled trials which examined the effect of caffeine on basketball performance outcomes including: free-throw, 3-point shooting accuracy, dribbling speed, vertical jump height, and linear and repeated sprints. Forty-six articles were identified of which 10 met the inclusion criteria. Improvements in vertical jump were identified in four of five studies, agility in two of four studies, and in linear and repeated sprints in two of three studies. No deterioration in basketball skills performance was observed in any studies. It is suggested that caffeine is useful for basketball players to improve the physical aspects of their game-play performance but there is little evidence of any change in skill-based performance at present. Further research should clarify the effects of caffeine on basketball performance in women and the role of individual genetic variation on caffeine metabolism. Basketball players and coaches should be aware of the properties of caffeine before ingesting it as an ergogenic supplement.

In-Season Nutrition Strategies and Recovery Modalities to Enhance Recovery for Basketball Players: A Narrative Review

Basketball players face multiple challenges to in-season recovery. The purpose of this article is to review the literature on recovery modalities and nutritional strategies for basketball players and practical applications that can be incorporated throughout the season at various levels of competition. Sleep, protein, carbohydrate, and fluids should be the foundational components emphasized throughout the season for home and away games to promote recovery. Travel, whether by air or bus, poses nutritional and sleep challenges, therefore teams should be strategic about packing snacks and fluid options while on the road. Practitioners should also plan for meals at hotels and during air travel for their players. Basketball players should aim for a minimum of 8 h of sleep per night and be encouraged to get extra sleep during congested schedules since back-to back games, high workloads, and travel may negatively influence night-time sleep. Regular sleep monitoring, education, and feedback may aid in optimizing sleep in basketball players. In addition, incorporating consistent training times may be beneficial to reduce bed and wake time variability. Hydrotherapy, compression garments, and massage may also provide an effective recovery modality to incorporate post-competition. Future research, however, is warranted to understand the influence these modalities have on enhancing recovery in basketball players. Overall, a strategic well-rounded approach, encompassing both nutrition and recovery modality strategies, should be carefully considered and implemented with teams to support basketball players' recovery for training and competition throughout the season.

Caffeinated Gum Does Not Influence RPE-Regulated Cadence in Recreationally-Active College Females Regardless of Habitual Caffeine Consumption

Caffeine (CAF) has been extensively studied for its ergogenic and analgesic effects during exercise. However, the majority of these studies have been conducted in male populations. This study investigated the effects of acute CAF chewing gum on self-selected exercise intensity during a rating of perceived exertion (RPE) production trial in active females (n = 16, 21.0 ± 2.8 y). Data were also analyzed based on habitual CAF consumption level. Participants completed a V̇O_2peak trial, followed by a familiarization and two randomized, triple-blinded experimental RPE production trials on an arm ergometer [clamped resistance, blinded to self-selected cadence (CAD)] with either CAF gum (300 mg; 4.8 ± 0.7 mg/kg^-1 body mass) or placebo (PLA), at a prescribed RPE of 4 and 7 (10 min each). Self-selected CAD did not statistically differ (p > 0.05) between CAF or PLA for an RPE4 (37.7 ± 1.6 vs. 37.6 ± 1.6 rev·min^-1) or RPE7 (42.9 ± 1.6 vs. 41.2 ± 1.7 rev·min^-1), respectively. There were no statistical differences between treatment groups for any other variables, except restlessness rating which was significantly higher (3.5 vs. 2.2; p = 0.03, d = 0.64) for the CAF group compared to PLA. Secondary analysis revealed no statistical differences for any variables between habitual consumers of low (23 ± 20 mg/day) or mod/high (195 ± 93 mg/day) CAF. Our data support previous studies examining CAF in women across different testing modalities and suggest that regardless of habitual CAF consumption, females might require higher doses of CAF to replicate subjective and physiological responses commonly observed using similar RPE production protocols in male participants. These findings support the need for additional investigations into female physiological and perceptual responses following CAF ingestion.

Effects of Caffeine and Caffeinated Beverages in Children, Adolescents and Young Adults: Short Review

The prevalence of ED consumption has increased over the past 10–15 years. Studies describing the effects of caffeine and caffeinated beverages show confusing results, so it seems important to regularly summarize the available facts, and in more detail. By a thorough analysis of more than 156 scientific papers, the authors describe the molecular background of absorption, as well as the positive and negative effects of different dosages of caffeine, just like its effects in physical activity and performance. ED and EDwA consumption is a regular habit of not only adults, but nowadays even of children and adolescents. There are no safe dosages described of caffeine or ED consumption for children. There are no positive short- or long-term effects of these compounds/products concerning developing brain functions, psycho-motor functions, or social development. Instead, there are many unpleasant side effects, and symptoms of regular or higher-dose ED consumption, especially at younger ages. This mini review describes many details of these unpleasant side effects, their severity, and motivations for consuming these compounds/products. In a quantitative research in Hungary (10–26 years, mean age: 15.6 ± 3.8 y, 1459 subjects, randomly chosen population), a survey based on a questionnaire asking people about their ED consumption habits was conducted. According to the data, 81.8% of the participants consumed EDs at least once, and 63.3% tried several products of the kind. A positive correlation was found between age and consumption (p < 0.001). The results show that a high proportion of this group often consumed EDwA, in many cases leading to harmful side-effects of caffeine overdose. In a sample of Hungarian high school and college students (17–26 years), ED consumption matched the international data, and only 19.7% of respondents did not use EDs at all (had never tasted an ED in their life).

Nutritional approaches to counter performance constraints in high-level sports competition

New Findings

What is the topic of this review?

The nutritional strategies that athletes use during competition events to optimize performance and the reasons they use them.

What advances does it highlight?

A range of nutritional strategies can be used by competitive athletes, alone or in combination, to address various event‐specific factors that constrain event performance. Evidence for such practices is constantly evolving but must be combined with understanding of the complexities of real‐life sport for optimal implementation.

Abstract

High‐performance athletes share a common goal despite the unique nature of their sport: to pace or manage their performance to achieve the highest sustainable outputs over the duration of the event. Periodic or sustained decline in the optimal performance of event tasks, involves an interplay between central and peripheral phenomena that can often be reduced or delayed in onset by nutritional strategies. Contemporary nutrition practices undertaken before, during or between events include strategies to ensure the availability of limited muscle fuel stores. This includes creatine supplementation to increase muscle phosphocreatine content and consideration of the type, amount and timing of dietary carbohydrate intake to optimize muscle and liver glycogen stores or to provide additional exogenous substrate. Although there is interest in ketogenic low‐carbohydrate high‐fat diets and exogenous ketone supplements to provide alternative fuels to spare muscle carbohydrate use, present evidence suggests a limited utility of these strategies. Mouth sensing of a range of food tastants (e.g., carbohydrate, quinine, menthol, caffeine, fluid, acetic acid) may provide a central nervous system derived boost to sports performance. Finally, despite decades of research on hypohydration and exercise capacity, there is still contention around their effect on sports performance and the best guidance around hydration for sporting events. A unifying model proposes that some scenarios require personalized fluid plans while others might be managed by an ad hoc approach (ad libitum or thirst‐driven drinking) to fluid intake.

A network pharmacology approach to explore the potential role of Panax ginseng on exercise performance

[Purpose]

As Panax ginseng C. A. Meyer (ginseng) exhibits various physiological activities and is associated with exercise, we investigated the potential active components of ginseng and related target genes through network pharmacological analysis. Additionally, we analyzed the association between ginseng-related genes, such as the G-protein-coupled receptors (GPCRs), and improved exercise capacity.

[Methods]

Active compounds in ginseng and the related target genes were searched in the Traditional Chinese Medicine Database and Analysis Platform (TCMSP). Gene ontology functional analysis was performed to identify biological processes related to the collected genes, and a compound-target network was visualized using Cytoscape 3.7.2.

[Results]

A total of 21 ginseng active compounds were detected, and 110 targets regulated by 17 active substances were identified. We found that the active compound protein was involved in the biological process of adrenergic receptor activity in 80%, G-protein-coupled neurotransmitter in 10%, and leucocyte adhesion to arteries in 10%. Additionally, the biological response centered on adrenergic receptor activity showed a close relationship with G protein through the beta-1 adrenergic receptor gene reactivity.

[Conclusion]

According to bioavailability analysis, ginseng comprises 21 active compounds. Furthermore, we investigated the ginseng-stimulated gene activation using ontology analysis. GPCR, a gene upregulated by ginseng, is positively correlated to exercise. Therefore, if a study on this factor is conducted, it will provide useful basic data for improving exercise performance and health.

Effects of Caffeine Consumption on Autologous Full-Thickness Skin Graft Healing in an Animal Model

Background There exists contradictory evidence that states both the beneficial and deleterious effects of caffeine on wound healing. The general population might unknowingly consume caffeine that negatively affects wound healing. The main objective of this study is to investigate the effect of daily caffeine consumption on wound healing, specifically full-thickness skin graft (FTSG).

Methods Forty Sprague–Dawley rats were randomized into four groups of equal size: control-dose (CD), low-dose (LD), medium-dose (MD), and high-dose (HD) caffeine groups. After autologous FTSG, all subjects in the intervention group were given daily pure caffeine gavage. The FTSG was explanted 7 days posttransplant. The graft viability, secondary contraction, and adherence were evaluated macroscopically, while fibroblast and collagen deposition was analyzed microscopically with hematoxylin eosin stain.

Results The least graft viability (72.8 ± 20.7%, clinical wound assessment scale [CWAS] 2.4), highest secondary contraction (11.4 ± 10.5%), and fibroblast count (331.8 ± 88.6 cells/5 high power fields) were observed in the MD group. More collagen synthesis was observed in subjects who consumed caffeine. The level of secondary contraction, fibroblast count as well as graft viability and collagen synthesis were positively correlated.

Conclusions Daily consumption of caffeine impairs graft viability when given in medium dose and increases collagen synthesis, irrespective of dosage. This study was in experimental rats; the results are not directly translatable to humans.