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The consumption of caffeine in response to insufficient sleep may impair the onset and maintenance of subsequent sleep. This systematic review and meta-analysis investigated the effect of caffeine on the characteristics of night-time sleep, with the intent to identify the time after which caffeine should not be consumed prior to bedtime. A systematic search of the literature was undertaken with 24 studies included in the analysis. Caffeine consumption reduced total sleep time by 45 min and sleep efficiency by 7%, with an increase in sleep onset latency of 9 min and wake after sleep onset of 12 min. Duration (+6.1 min) and proportion (+1.7%) of light sleep (N1) increased with caffeine intake and the duration (-11.4 min) and proportion (-1.4%) of deep sleep (N3 and N4) decreased with caffeine intake. To avoid reductions in total sleep time, coffee (107 mg per 250 mL) should be consumed at least 8.8 h prior to bedtime and a standard serve of pre-workout supplement (217.5 mg) should be consumed at least 13.2 h prior to bedtime. The results of the present study provide evidence-based guidance for the appropriate consumption of caffeine to mitigate the deleterious effects on sleep.

Background/Objectives: The aim of this study was to compare the different forms of caffeine (CAF) administration in CrossFit® participants. The countermovement jump (CMJ), the rate of perceived exertion (RPE), the total number of repetitions, and the maximum (HRmax) and mean heart rate (HRmean) were evaluated. Methods: Fourteen males with more than six months of continuous CrossFit® training (30.9 [5.62] years, 179 [1.33] cm, 78 [5.75] kg, 24.3 [1.33] kg·m-2) participated in this randomized, placebo-controlled, crossover study. Participants were randomized in a repeated measures design using caffeine capsule (CC), caffeine chewing gum (CCG), and caffeine mouth rinse (CMR) protocols, along with a placebo group (PG). Participants were unaware of whether any of the delivery methods contained caffeine. A 7-day washout period before each crossover was used. To ensure ecological validity, we replicated the real-world practice of CAF ingestion 30 min prior to training, mirroring typical athlete pre-workout routines. The participants of CrossFit® performed the 'Cindy' protocol, and the CMJ as a primary outcome was measured pre- and post-intervention, while the RPE, HR, and the number of repetitions were tracked at the end of the workout for comparisons. Results: No significant differences were found between CAF forms in internal load measures (RPE, HRmax, HRmean) or the number of repetitions. While no changes were observed with other CAF forms, CMR significantly improved the CMJ performance compared to the baseline (Δ: +3.5; Cohen's dunb: 0.51], which exceeded the estimated SWC by approximately three-fold. However, the inferential analysis revealed no significant main effects of the caffeine administration method on any measured outcomes. Conclusions: While CAF delivery forms did not improve internal load measures or performance parameters, such as the RPE, HR, or the total number of repetitions, the caffeine mouth rinse (CMR) showed a potentially meaningful improvement in CMJ performance after CrossFit® training in participants with a certain level of experience.

BACKGROUND: Pre-workout multi-ingredients are designed to enhance energy levels and acutely increase exercise performance. This study compared the effectiveness of ingesting an admixture providing caffeinated ingredients and plant-based protein enriched with amino acids versus carbohydrates alone on body composition, hypertrophy and physical performance. METHODS: Forty-three middle-aged physically active individuals (26 peri- and post-menopausal females and 17 males) completed the study after being randomly assigned to one of the following intervention groups: pre-workout (PREW n = 24, 54 ± 4 years, body mass 77.6 ± 16.0 kg) or a carbohydrate-only comparator (COMP n = 19, 52 ± 4 years, body mass 80.6 ± 16.0 kg). Measurement of fat and fat-free mass (via plethysmography), waist and hip circumferences, muscle thickness (via ultrasound), strength, power output and muscle endurance performance were collected before and after a 6-week resistance training programme performed 3 times per week. Treatment consisted of ingesting 30g of the assigned supplement, mixed with 400mL of plain water, 15min before each workout session. RESULTS: Both groups significantly (p < 0.05) reduced fat mass (mean ± SD) (PREW -1.4 ± 1.6 kg; COMP -1.0 ± 1.5 kg), increased fat-free mass (PREW +0.9 ± 1.1 kg; COMP + 0.8 ± 0.9 kg); vastus lateralis (PREW +0.2 ± 0.2 cm; COMP + 0.1 ± 0.6 cm), and elbow flexors (PREW +0.5 ± 0.3 cm; COMP + 0.4 ± 0.2 cm) muscle thickness. Only the PREW group showed a significant reduction in the waist circumference (-1.8 ± 1.8 cm, p < 0.01). However, no significant differences between groups (PREW vs. COMP) were identified at post-intervention. Isometric force, countermovement jump, medicine ball throw, and upper and lower body muscle endurance performance improved (p < 0.05) for both treatments, with no difference between groups. CONCLUSION: Except for waist circumference reduction, ingesting a pre-workout vegan protein-based caffeinated supplement promotes no further resistance training benefits in middle-aged individuals.

Caffeine and beta-alanine are widely used in multi-ingredient pre-workout supplements believed to enhance resistance training, but their specific role in driving this effect remains unclear. The current study employed a randomized, triple-blinded, placebo-controlled and crossover experimental design to explore the acute effects of caffeine (200 mg), beta-alanine (3 g), or their combination (200 mg caffeine and 3 g beta-alanine; C+B-A) administered 30 min prior to resistance training (RT) on mechanical, physiological, and perceptual variables. Twenty-one young resistance-trained males (age = 23.5 ± 4.5 years, body mass = 82.1 ± 10.2 kg) visited the laboratory on six occasions: one familiarization session, one preliminary testing session for load determination, and four experimental sessions which differed only in supplementation condition and involved four supersets of bench press and bench pull exercises. The supplement condition did not significantly affect any mechanical variables (p ≥ 0.335), except for the velocity of the last repetition of the set, where beta-alanine produced lower values (0.383 m/s) compared to placebo (0.407 m/s; p < 0.05), with no differences observed for C+B-A (0.397 m/s) and caffeine (0.392 m/s). Heart rate was consistent across the different supplement conditions with the exception of the higher values observed immediately before the start of the RT session for placebo compared to caffeine (p = 0.010) and C+B-A (p = 0.019). Post-RT blood lactate concentration (p = 0.384), general and local ratings of perceived exertion (p = 0.177 and 0.160, respectively), and readiness (p = 0.281-0.925), did not differ significantly between supplement conditions. Selected supplements have minimal effects on performance and physiological responses in agonist-antagonist upper-body superset RT not leading to failure. © 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

A pre-workout supplement's (PWS; 200 mg caffeine, 3.3 g creatine monohydrate, 3.2 g β-alanine, 6 g citrulline malate and 5 g branched chained amino acid (BCAA) per dose) acute effects on the alactic (jumping, sprinting, agility), lactic (Running-Based Anaerobic Sprint Test, RAST) and aerobic performance (Yo-Yo Intermittent Recovery Test Level 1, Yo-Yo IRL1 VO2max) of well-trained basketball players was investigated in this double-blind placebo-controlled study. Thirty players (age 18-31 years, height 166-195 cm, weight 70.2-116.7 kg, body fat 10.6-26.4%) were allocated to pre-workout (PWS, n = 15) or placebo (PL, n = 15) groups. Half of the participants in each group performed the evaluations without PWS or PL, while the rest consumed PWS or PL 30 min before the assessments (1st trial) and vice versa (2nd trial). Significant improvements in counter-movement jump (CMJ) (PWS: 4.3 ± 2.1%; PL: 1.2 ± 1.0%), agility (PWS: -2.9 ± 1.8%; PL: 1.8 ± 1.7%), RAST average (PWS: 18.3 ± 9.1%; PL: -2.2 ± 2.0%), minimum power (PWS: 13.7 ± 8.9%; PL: -7.5 ± 5.9%), and fatigue index (PWS: -25.0 ± 0.9%; PL: -4.6 ± 0.6%) were observed in the PWS group vs. the PL group (p < 0.05). No differences were found regarding sprinting, aerobic performance, and blood lactate concentrations. Thus, although players' alactic and lactic anaerobic performance could be improved, peak power, sprinting and aerobic performance are not.

AIM: The acute myocellular responses of caffeine supplementation during resistance exercise (RE) have not been investigated. β2-Adrenergic receptors (β2AR) may be a target of the stimulatory effects of caffeine and stimulate bioenergetic pathways including protein kinase A (PKA), and mitogen-activated protein kinases (MAPK). PURPOSE: Elucidate the effects of pre-workout supplementation on signaling responses to an acute RE bout. METHODS: In a randomized, counter-balanced, double-blind, placebo-controlled, within-subject crossover study, ten resistance-trained males (mean ± SD; age = 22 ± 2.4 years, height = 175 ± 7 cm, body mass = 84.1 ± 11.8 kg) consumed a caffeine containing multi-ingredient pre-workout supplement (SUPP) or color and flavor matched placebo (PL) 60 min prior to an acute RE bout of barbell back squats. Pre- and post-exercise muscle biopsies were analyzed for the phosphorylation (p-) of β2AR, PKA, and MAPK (ERK, JNK, p38). Epinephrine was determined prior to supplementation (baseline; BL), after supplementation but prior to RE (PRE), and immediately after RE (POST). RESULTS: Epinephrine increased at PRE in SUPP (mean ± SE: 323 ± 34 vs 457 ± 68 pmol/l; p = 0.028), and was greatest at POST in the SUPP condition compared to PL (5140 ± 852 vs 2862 ± 498 pmol/l; p = 0.006). p-β2AR and p-MAPK increased post-exercise (p < 0.05) with no differences between conditions (p > 0.05). Pearson correlations indicated there was a relationship between epinephrine and p-β2AR in PL (r = - 0.810; p = 0.008), and p-β2AR and ERK in SUPP (r = 0.941; p < 0.001). CONCLUSION: Consumption of a caffeine containing pre-workout supplement improves performance, possibly through increases in pre-exercise catecholamines. However, the acute myocellular signaling responses were largely similar post-exercise. © 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

The search to increase physical performance is inherent to physical activity practitioners, and nutrition features are among the alternatives to seeking such an increase. The literature from the area has shown that different substances can promote beneficial effects over physical performance. One substance that has come into the spotlight is theacrine, an alkaloid similar to caffeine, which aims to increase physical performance. However, the studies on this supplement are scarce. Therefore, this study is a randomized, controlled trial that aimed to verify the effects of theacrine supplementation over physical performance in young male athletes, by applying a battery of physical tests. Twenty-two male amateur flag-football athletes were recruited. Subjects were divided into two groups and assessed at two moments, which were 72 h apart. The first assessment served as a basal measurement. In the second, the subjects ingested the supplement or a placebo 60 min before the following tests: sextuple jump, agility T test, 30 m sprint, 40 s run test (Matsudo test), and 12 min run test (Cooper test). There was no difference between the groups in any of the tests. Therefore, the findings of this study do not support the use of theacrine to increase physical performance.

This investigation aimed to determine the effect of a multi-ingredient pre-workout supplement (MIPS) on heart rate (HR), perceived exertion (RPE), lactate concentration, and time to fatigue (TTF) during a running task to volitional exhaustion. Eleven NCAA Division I cross-country runners (20 ± 2 year; height: 171 ± 14 cm; weight: 63.5 ± 9.1 kg) participated in this randomized, double-blind, placebo-controlled cross-over study. Bayesian statistical methods were utilized, and parameter estimates were interpreted as statistically significant if the 95% highest-density intervals (HDIs) did not include zero. TTF was increased in the MIPS condition with a posterior Meandiff = 154 ± 4.2 s (95% HDI: -167, 465) and a 0.84 posterior probability that the supplement would increase TTF relative to PL. Blood lactate concentration immediately post-exercise was also higher in the MIPS condition compared to PL with an estimated posterior Meandiff = 3.99 ± 2.1 mmol (95% HDI: -0.16, 7.68). There were no differences in HR or RPE between trials. These findings suggest that a MIPS ingested prior to sustained running at lactate threshold has an 84% chance of increasing TTF in highly trained runners and may allow athletes to handle a higher level of circulating lactate before reaching exhaustion.

PURPOSE: Consumption of caffeine or caffeine containing pre-workout supplements (SUPP) augments steroid hormone responses to resistance exercise (RE). However, the activation of glucocorticoid (GR) and androgen receptors (AR) following RE SUPP has not been investigated. The purpose of this study was to determine the influence of a pre-workout supplement on AR and GR phosphorylation following RE. METHODS: In a randomized, counter-balanced, double-blind, placebo-controlled, within-subject crossover study, ten resistance-trained males ((X¯±SD, age = 22 ± 2.4 yrs, hgt = 175 ± 7 cm, body mass = 84.1 ± 11.8 kg) performed four sets of 8 repetitions of barbell back squats at 75% of their 1-repetition maximum (1-RM) with two minutes of rest between sets and a fifth set of barbell back squats at 60% of 1-RM until concentric failure. A SUPP or flavor and color matched placebo (PL) was consumed 60-minutes prior to RE. Vastus lateralis muscle biopsies were obtained prior to supplementation at rest (BL), and ten minutes post-exercise (POST). Biopsies were analyzed for phosphorylated GR (ser134, ser211, and ser226) and phosphorylated AR (ser81, ser213, ser515, ser650) via western blotting. RESULTS: pGRser134 decreased, and pGRser226 increased following RE (p < 0.05) with no difference between conditions (p > 0.05). pGRser211 was unchanged after RE (p > 0.05). pARser515 increased, and total AR expression decreased after RE (p < 0.05) in SUPP only. Testosterone and cortisol were not different between SUPP and PL at POST (p > 0.05). CONCLUSION: RE influences AR and GR phosphorylation, and SUPP minimally influences this response in the early recovery period.

BACKGROUND AND OBJECTIVES: Esports place exceptional demands on neuropsychological capacities; however, a systematic and quantitative synthesis of the specific efficacy of nutritional interventions across various tasks and competitive populations remains absent. This study aims to evaluate the impact of nutritional supplementation on cognitive function and competitive performance in esports players and to explore key moderating variables. METHODS: Electronic databases, including Web of Science, PubMed, and Scopus, were searched (up to January 25, 2026). Thirteen randomized controlled trials (RCTs) met the inclusion criteria. A three-level random-effects model was employed to calculate the pooled effect size (Hedges' g), with sources of heterogeneity explored through subgroup analyses and meta-regression. RESULTS: Nutritional interventions significantly enhanced esports-related performance (g = 0.92), with the most pronounced benefits observed in processing speed (g = 1.18) and executive function (g = 1.06). Subgroup analyses revealed significant gains in both professional (g = 0.97) and amateur groups (g = 0.92), while the improvement in first-person shooter (FPS) games (g = 0.96) appeared to surpass that in multiplayer online battle athlete (MOBA) games. Meta-regression indicated no significant linear correlation between caffeine dosage and effect size. GRADE assessment categorized the quality of evidence mostly as "low" to "moderate." CONCLUSIONS: Nutritional interventions demonstrate significant potential for optimizing multidimensional cognitive performance in esports players, particularly in enhancing fundamental reaction speed and high-level decision-making processes. While the findings exhibit a degree of robustness, their practical application should be cautiously evaluated within specific competitive contexts due to current limitations in evidence certainty and significant interstudy heterogeneity. Future research characterized by gender balance and mechanistic orientation with long-term intervention protocols is warranted to elevate the level of clinical evidence.

BACKGROUND: Although caffeine is widely used in athletes due to its ergogenic effects, the effects of its main metabolite, paraxanthine, on performance and sleep have not been adequately investigated. PURPOSE: This study aimed to comparatively investigate the effects of caffeine and its main metabolite paraxanthine on rowing performance and sleep quality. METHODS: The study was designed as a randomized, double-blind, crossover study and included 14 male university-level rowers (21.6 ± 1.9 age; 2.2 ± 1 years of rowing experience). The participants participated in 2000-m rowing ergometer time trials under four different supplementation conditions (caffeine + paraxanthine, caffeine + placebo, paraxanthine + placebo, and placebo with 200 mg each). Performance data (completion time, mean power, and heart rate), sleep quality, and daytime sleepiness were assessed by subjective scales. The data were analyzed by repeated-measures analysis of variance (ANOVA) and Bonferroni post-hoc tests. RESULTS: Compared with the placebo, the combined caffeine + paraxanthine condition was associated with faster 2000-m performance and higher mean power output (p = 0.044; Cohen's d = 0.30). Caffeine alone and paraxanthine alone did not show clear evidence of performance improvement in this sample, although estimates favored both conditions versus placebo. Conditions containing caffeine were associated with poorer subjective sleep quality, whereas paraxanthine alone showed more favorable sleep-related outcomes. CONCLUSION: These results indicate that the combined ingestion of caffeine and paraxanthine elicited the most pronounced performance benefits, while paraxanthine alone did not demonstrate clear standalone ergogenic efficacy at the administered dose. However, paraxanthine was associated with better subjective sleep outcomes compared to caffeine, suggesting that its potential value may be related more to tolerability rather than superior performance enhancement, particularly for athletes training in the evening. Study limitations, including the small sample size and lack of objective sleep measures, should be considered when interpreting the results. PRACTICAL APPLICATIONS: Paraxant

Objectives: To determine whether caffeine supplementation and its expectancy influence muscle strength (ST) and muscle endurance (ME) using a balanced-placebo design. Methods: Using a randomized, double-blind, balanced-placebo design, resistance-trained men (18-30 years; n = 16) participated in two assessment/familiarization visits (demographics; one repetition maximum (1RM) followed by four counterbalanced sessions: C/C (informed caffeine/used caffeine), P/C (informed placebo/used caffeine), C/P (informed caffeine/used placebo), P/P (informed placebo/used placebo). Caffeine dose was 5 mg/kg. Peak torque (PT) and maximum work (MW) were measured in the knee extensors at 0, 60, 180, and 300°/s, which was followed by ME testing (three sets of maximal repetitions using 60%1RM). Capillary blood lactate was measured after ME testing. Results: Caffeine increased PT only during static and 60°/s contractions (4%; p ≤ 0.003; d = 0.3 for both speeds), while MW increased across all speeds (4%; p < 0.001; d = 0.2). Caffeine did not increase ME (3%; p = 0.184; d = 0.1), but it did increase blood lactate levels (1.2 mmol/L; p < 0.001; d = 0.7). Caffeine expectation did not improve ST or ME, but increased blood lactate levels (0.7 mmol/L; p = 0.003; d = 0.4). Across ST and ME, responses to caffeine were markedly heterogeneous, with 50-88% of individuals considered responders (∆ > 0), and improvements in responders ranged from 1-16%. Conclusions: Caffeine significantly increased ST, despite ME increasing in 50% of participants, this was not significant. No placebo effect was observed in ST or ME, but it significantly increased lactate. Further research is necessary to elucidate the mechanisms behind this variability in the ME response, especially the role of fiber-type predominance.

Caffeine enhances endurance performance but may impair shooting accuracy, creating a potential trade-off for overall biathlon performance. In a randomized, placebo-controlled, crossover study, seven elite male biathletes consumed caffeine (3 mg/kg) or taste-matched placebo 60 min before a simulated biathlon competition consisting of five "laps" of 6-min treadmill skiing interspersed by four five-shot bouts. Participants further performed precision shooting (20 prone and 20 standing) pre- and postcompetition. Caffeine increased distance covered in Laps 1 (1,824 ± 73 vs. 1,772 ± 66 m; p = .03, dz = 1.12) and 2 (1,801 ± 92 vs. 1,776 ± 84 m; p = .02, dz = 1.19) but did not improve total distance (p = .06). Blood lactate (p = .01, ηp2=.85) and ventilation (p < .001, ηp2=.90) increased with caffeine. Heart rate (p = .07) and perceived exertion (p = .69) did not differ between conditions. Caffeine impaired shooting accuracy in standing (72.9 ± 16.0% vs. 82.9 ± 7.6%; p = .03, dz = 0.87), but not prone. Integrated race times did not differ between conditions for individual (71.72 ± 5.27 vs. 71.58 ± 4.57 min), mass start (52.45 ± 3.67 vs. 52.57 ± 3.27 min), or pursuit (44.18 ± 3.18 vs. 44.23 ± 2.83 min; all p > .77) formats. Caffeine impaired postexercise precision shooting in prone position (88.9 ± 6.0% vs. 93.3 ± 7.5%; p = .04, dz = 0.65). Our findings highlight task-specific effects of caffeine, emphasizing the importance of tailoring supplementation to integrated performance demands.

This study examined whether CYP1A2 (rs762551) genotype modulates the acute ergogenic effects of caffeine on muscular strength and endurance performance in resistance-trained men and women. Ninety-four resistance-trained participants (47 females, 47 males; 39 AA, 44 AC, 11 CC) completed a randomized, triple-blind, placebo-controlled, crossover trial. Participants ingested 3 mg/kg of caffeine or placebo before performing standardized bench press and back squat tests. Mean velocity was measured to assess strength performance against different loads (25%-90%) and muscular endurance during a single set performed to failure at 65% 1RM. Data were analyzed using ANCOVA with supplement, genotype, and sex as factors. Caffeine significantly improved strength and endurance performance across conditions (p < 0.01, ηp2 = 0.077-0.294). Mean velocity increased by 4%-12% in AA and 3%-9% in AC individuals, particularly at 50%-90% 1RM, whereas CC carriers showed minor changes (≤ 4%). Supplement by genotype interaction was noted only at 90% 1RM in mean velocity (p < 0.05, ηp2 = 0.094). In the muscular endurance test, mean velocity improved by 4%-6% in AA, 3%-4% in AC, and 2%-6% in CC. No sex differences or ergolytic effects were observed. Acute ingestion of 3 mg/kg caffeine enhances strength and endurance performance in resistance-trained men and women. Although CYP1A2 genotype did not alter the overall effect, benefits were greatest in AA, intermediate in AC, and minimal in CC carriers. These findings support low-dose caffeine as an effective and safe ergogenic aid in resistance training regardless of sex, with individual variability partly explained by genotype. © 2026 The Author(s). Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd.

The purpose of this study is to investigate the effects of combined carbohydrate (CH) and caffeine (CAF) supplementation on the sports performance of basketball players. A randomized crossover controlled experimental design was employed. A total of 32 collegiate-level basketball players were randomly assigned to one of the four groups: placebo (PLA), CH (30 g/h glucose solution) group, CAF (3 mg/kg body mass) group, and CH + CAF (combined intervention) group. Participants underwent a series of tests, including the countermovement jump (CMJ), 20-m sprint (20 m), change-of-direction and acceleration test (CODAT), Yo-Yo intermittent recovery test level 1 (Yo-Yo), free throw (FT) test, and straight-line dribbling speed (SLDS) test. Heart rate (HR) and blood lactic acid (BLA) levels were also monitored during the tests. The results revealed that, in the CMJ, 20 m, and CODAT tests, the CAF and CH + CAF groups outperformed the PLA group significantly (p < .05). In the Yo-Yo test, both the CH and CH + CAF groups demonstrated significantly better performance compared with the PLA group (p < .01). However, no significant differences were observed among the groups in the FT and SLDS tests (p > .05). Notably, the BLA levels in the CAF group were significantly higher than those in the PLA and CH groups 1-min postexercise (p < .05), and also significantly higher than in the CH + CAF group (p < .01). Three min after exercise, BLA levels in both the CH + CAF and PLA groups increased significantly (p < .05), with the CH + CAF group showing a greater increase compared with the CH group (p < .01). During exercise, the HR in the CH group was significantly lower than in the PLA group (p < .01), while the HR in the CAF group was significantly higher than in the PLA group (p < .01). Furthermore, the HR in the CH group was significantly lower compared with the CAF group (p < .01), and the HR in the CH + CAF group was significantly higher than in the CAF group (p < .01). After exercise, the HR in the CH group remained significantly lower than in the CAF group (p < .01). In conclusion, the combined supplementation of CH + CAF can effectively improve the overall sports performance of bask

BACKGROUND: Esports has become a globally popular competitive activity. The performance of esports athletes depends not only on daily skill training but also on cognitive function, reaction speed, and psychological mood. In recent years, nutritional supplements have attracted widespread attention as a potential adjunctive treatment. However, their actual effects lack systematic evaluation. Objective: The primary aim of this study is to comprehensively review existing evidence and assess the impact of nutritional supplements on the performance of esports athletes, including cognitive, psychological, and gaming aspects. METHODS: As of June 17, 2025, randomized controlled trials (RCTs) or randomized crossover trials investigating the effects of nutritional supplements on cognitive function, psychological mood, and competitive performance in esports players were retrieved from the PubMed, Scopus, Web of Science, and Embase databases. Two researchers independently extracted key information and data from the literature. The methodological quality of the included studies was assessed using the Physical Therapy Evidence Database (PEDro) scale. RESULTS: A total of 13 randomized controlled trials were included, comprising 10 randomized crossover trials and 3 randomized controlled trials. The study population comprised 466 participants. The methodological quality of the studies, assessed by the PEDro scale (score range 6-10), was good to excellent. The studies included 18 nutritional supplement protocols, with 14 protocols involving pure caffeine or caffeine-containing supplements. Other protocols included active substances such as inositol-enhanced arginine silicate (ASI + I), γ-aminobutyric acid (GABA), and microalgae extracts. Based on existing evidence, some nutritional supplements are associated with three aspects of competitive performance among esports players: 1) Esports players demonstrate significant improvements in attention and executive function, which are closely related to gaming. 2) Improvements in esports players' psychological mood are manifested as increased vitality and reduced fatigue/negative emotions. 3) Improvements in gaming performance are primari

Background: Explosive lower limb power, a critical determinant of success in volleyball, is a prime candidate for focused research. Consequently, nutritional supplements are commonly employed to gain an ergogenic edge. Despite this widespread practice, a comprehensive and evidence-based ranking of supplements for improving this key attribute is lacking, leaving athletes and practitioners without targeted evidence to guide decisions. Methods: PubMed, Web of Science, CENTRAL, and Embase were searched from inception to 1 August 2025. We included RCTs in volleyball athletes (≥14 years) with ≥1-week interventions and relevant explosive lower limb performance outcomes. A Bayesian NMA estimated effects with 95% credible intervals (CrIs) and SUCRA; certainty was appraised with CINeMA. Results: A total of 35 RCTs (n = 838 volleyball athletes) examining 13 different supplements were included. The results indicated that β-alanine was associated with the greatest improvement in vertical jump (MD 4.6; 95% CrI 1.2-7.8), followed by creatine (MD 3.7; 0.57-6.9) and caffeine (MD 2.1; 0.06-4.1). It also appeared to be the most promising method for substantially increasing lower limb peak power (SMD 1.1; 0.21-2.0). No statistically significant improvement was found in lower limb mean power, and no serious adverse events were reported. Conclusions: Among volleyball athletes, β-alanine appeared most promising effective supplement for enhancing key components of explosive lower limb performance, specifically vertical jump height and peak power. Creatine and caffeine are also effective for improving vertical jump height. However, these findings are based on low-to-moderate certainty of evidence; they should be interpreted with caution and regarded as preliminary. Supplement strategies should be individualized by age and competitive level; further, high-quality, standardized randomized controlled trials are warranted to validate these initial observations.

OBJECTIVE: This study examined whether caffeine (4 mg/kg) enhances upper- and lower-body maximal strength and muscular power by increasing muscle recruitment and reducing in ratings of perceived exertion (RPE) and pain perception. METHODS: Fourteen resistance-trained males completed two randomized trials involving either caffeine ingestion (4 mg/kg) or a placebo. Sixty minutes after ingesting capsule, participants performed maximal strength tests (one-maximum repetition [1RM]) followed by muscular power assessments (bar velocity and power output) at 25%, 50%, 75%, and 90% of 1RM, performing 3, 2, 1, and 1 repetitions, respectively during bench press and back squat. Outcome measured included 1RM, mean and peak velocity, mean and peak power output, surface electromyographic activity of the prime movers, RPE, and pain perception. RESULTS: Compared to placebo, caffeine significantly increased 1RM in both bench press and back squat, while reducing RPE and pain perception and enhancing root mean square (RMS) activity in the gluteus maximus (all p < 0.05), though it did not affect the median frequency (MDF) or mean frequency (MF) in any studied muscle (all p > 0.05). The percent improvement in 1RM was larger (+7.0 ± 2.9% vs. + 4.1 ± 2.9%; p < 0.05) for the back squat than for the bench press. Furthermore, caffeine significantly increased muscular power during both exercises (all p < 0.05), without affecting surface electromyographic activity of the prime movers, RPE, and pain perception (all p > 0.05). CONCLUSION: Ingesting a caffeine capsule at a dose of 4 mg/kg enhances maximal strength by increasing muscle recruitment and reducing RPE and pain perception, with greater improvement observed in the bench press than in the back squat. Caffeine also improves muscular power in both exercises without altering muscle recruitment or subjective perception.

This study aims to evaluate the influence of the CYP1A2 genotype on the exercise performance of athletes and physically active individuals with caffeine supplementation. We followed the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis. The search was performed up to May 2025 and included the following databases: PubMed, EMBASE, Scopus, Web of Science, Cochrane Central Register of Controlled Trials, CINAHL, LILACS, and SPORTDiscus. Only randomized clinical trials evaluating the effects of caffeine supplementation and the influence of the CYP1A2 genotype on exercise performance were included. The risk of bias was evaluated using the updated version of the Cochrane tool for assessing bias risk in randomized trials (RoB 2). We included 19 studies, involving 732 participants, and published between 2012 and 2024. Dosages of caffeine supplementation ranged from 2 to 9 mg/kg. Although there is no consensus among all studies, caffeine supplementation has shown positive results in sports performance in individuals with the AA genotype, as well as positive for AC individuals with smaller effect sizes, and null or negative for individuals with the CC genotype. The majority (84%) of the included studies were classified as "some concerns" in our risk of bias analysis, with only two studies classified as having a low risk of bias. Caffeine may enhance athletic performance in various sports modalities and physical tests in individuals with the AA genotype, may also demonstrate marginal improvement in AC individuals, and has null or detrimental effects on individuals with the CC genotype.

BACKGROUND: While caffeine has been proposed to stimulate hair growth, its safety and efficacy remain unclear. This systematic review evaluates the effects of caffeine interventions on hair loss and growth outcomes. METHODS: A systematic review of seven databases, including PubMed, Medline, and Embase, was conducted in August 2023. Original studies investigating caffeine's effects on hair loss were included. Study quality was assessed using the National Institute of Health Study Quality Assessment Tools. Outcomes of interest included caffeine intervention types and their effects on hair growth. RESULTS: Of 587 citations, nine studies met the inclusion criteria: five randomized controlled trials, three prospective cohort studies, and one twin-twin cohort study. Most studies investigated topical caffeine; one assessed oral caffeine intake. Topical caffeine consistently demonstrated hair growth or reduced hair loss with minimal adverse effects. However, none of the studies used tattooed or marked scalp areas for hair counts. CONCLUSIONS: Caffeine appears to be a safe and promising potential treatment for hair loss. Topical caffeine shows potential as a therapeutic option, though further large-scale randomized controlled trials with standardized outcome measures are needed.

OBJECTIVES: To investigate the effects of acute coffeeberry extract ingestion on soccer-specific technical skill performance, sprint performance, high-intensity running capacity, and subjective perceptions of fatigue, energy, and alertness during a soccer match simulation in academy soccer players. DESIGN: Double-blind, randomised, placebo-controlled, crossover trial. METHODS: Twenty trained male soccer players completed two experimental trials (coffeeberry extract [300 mg] and placebo [flavour and colour matched] beverages), separated by 7-14 days. Each trial, conducted 1 h after ingestion of the test beverages, included a 45-min half soccer match simulation incorporating dribbling, sprinting, and passing tasks, followed 5 min later by a high-intensity running-to-fatigue protocol. Subjective measures (fatigue, mental/physical energy), physiological data (glucose, lactate), technical skills and running outcomes were assessed. Blood samples were analysed for chlorogenic acid and caffeine concentrations. RESULTS: Coffeeberry ingestion resulted in greater maintenance of passing speed (p < 0.01) and accuracy (p < 0.01) compared to placebo, most evident on short passes. No meaningful significant differences were observed in sprint performance, dribbling or running capacity. Subjective fatigue increased, and energy scores declined, similarly across trials. No difference was observed in blood glucose or lactate responses. No chlorogenic acid or caffeine was detected at quantifiable concentrations in plasma samples post-ingestion. CONCLUSIONS: Acute ingestion of coffeeberry extract improved select aspects of soccer skill performance, particularly short-passing speed/accuracy, in academy soccer players. These findings suggest a potential cognitive or neuromuscular mechanism, independent of metabolic effects. Further research is warranted to explore the time course of chlorogenic acid absorption and its potential mechanistic role in skill performance.

BACKGROUND: Caffeine is a well-known ergogenic aid that can enhance physical and cognitive performance. However, it often induces side effects, such as anxiety and overstimulation, which can be problematic in high-pressure sports like wrestling. L-theanine, a non-stimulant amino acid found in tea, may help mitigate these effects by promoting a calm yet focused mental state. This study aimed to investigate the acute effects of caffeine, L-theanine, and their combination on physical performance, cognitive function, and anxiety in elite male wrestlers. METHODS: In a double-blind, placebo-controlled, crossover design, 12 elite male wrestlers (21.8 ± 2.1 years) completed four test sessions under randomized conditions: placebo (PLA), caffeine (CAF; 3 mg/kg), L-theanine (THE; 3 mg/kg), and caffeine + L-theanine (CAF+THE; 3 mg/kg each). After 60 minutes, athletes performed the wall-squat test, vertical jump height (VJH), medicine ball throw (MBT), handgrip strength, and the Specific Wrestling Fitness Test (SWFT). Cognitive function was assessed pre- and post-SWFT using a computerized Stroop test. Anxiety was assessed using the State-Trait Anxiety Inventory (STAI), and side effects were recorded. RESULTS: CAF+THE outperformed PLA in wall-squat time (p = 0.001), MBT (p = 0.005), VJH (p = 0.011), and grip strength (p = 0.004). SWFT throw count was highest in CAF+THE versus all other conditions (p < 0.001). Post-SWFT Stroop reaction time was faster in CAF+THE than PLA (p = 0.004) and THE (p = 0.036), and accuracy was also higher (p = 0.009 vs PLA). CAF alone increased state anxiety compared to PLA (p = 0.021), while CAF+THE reduced anxiety to below placebo levels (8% incidence vs 33%). Trait anxiety was lower in CAF+THE compared to CAF (p = 0.018). The prevalence of caffeine-induced tachycardia (92%) was notably reduced under CAF+THE (17%). CONCLUSION: CAF+THE (3 mg/kg each) enhances elite wrestlers' strength, endurance, cognitive speed, and accuracy while reducing anxiety and physiological side effects commonly associated with caffeine alone. This combination represents a safe, practical supplement strategy for combat sports athletes who must maintain explosive performance

The purpose of this study was to confirm reduced training metrics previously associated with a ketogenic low-carbohydrate (CHO) high-fat diet (LCHF) and investigate their attenuation with caffeine supplementation. At baseline, n 21 elite race-walkers followed a high CHO availability (HCHO) diet and performed a tempo hill session (14 km with a 450 m elevation gain). Athletes were then assigned to either the HCHO or LCHF in a parallel groups design for 3 weeks, where the 14 km tempo hill session was repeated each week. On weeks 2 and 3, in a randomised crossover allocation, all participants received 3 mg/kg caffeine or placebo (gum), 20 min before the session. Race-walking speed, heart rate, ratings of perceived exertion, blood metabolites and Stroop word-colour test metrics were collected. Although LCHF athletes walked faster at baseline compared with HCHO (P = 0·049), the HCHO group improved by week 2 (P = 0·009) and week 3 (P = 0·007), whereas the LCHF group was significantly slower in Week 1 (P < 0·001) and Week 2 (P = 0·026) compared with baseline. During the 14 km hill session, within-group analysis shows that athletes walked significantly faster (P = 0·010) and at a higher percentage of vVO2max (P = 0·007) when using caffeine compared with a placebo. Between-group differences remained present, with HCHO athletes walking at a higher percentage of vVO2max than those adhering to the LCHF diet (P = 0·035). No interaction between supplement treatment and dietary group occurred (P = 0·640). Caffeine supplementation partially reversed the performance impairment associated with an LCHF diet, but training quality remained lower than the combination of caffeine and high CHO availability.