Caffeine's ergogenic potential in vertical jumping remains contested, particularly at dosages compliant with collegiate athletic regulations. The NCAA enforces a caffeine urinary threshold equivalent to ~5 mg/kg body mass, yet evidence supporting its efficacy in enhancing explosive performance among trained athletes is inconsistent. This study examined whether acute caffeine ingestion at this threshold improves squat jump (SJ) and countermovement jump (CMJ) performance in NCAA Division II student-athletes, while exploring sex-specific responses and trial-to-trial variability.

Forty NCAA Division II athletes (18 females, 22 males; 21.3 ± 2.4 years) participated in a single-blind, randomized, crossover trial. Participants ingested 5 mg/kg caffeine or placebo, followed by SJ and CMJ testing on a force platform 60 minutes post-consumption. Three trials per jump type were retained to preserve intra-individual variance. Linear mixed-effects models (LMMs) assessed fixed effects of condition, sex, and trials, with random intercepts and slopes accounting for individual variability. A priori power analyses guided sample size determination, targeting sensitivity to detect small-to-medium effects (Cohen's f ≥ 0.2).

Caffeine elicited trivial, non-significant differences in SJ (β =  -0.24 cm, p = 0.646) and CMJ (β =  -0.71 cm, p = 0.183) heights compared to placebo. Males outperformed females in both SJ (Δ = 9.50 cm, p < 0.001) and CMJ (Δ = 11.30 cm, p < 0.001), though no condition-by-sex interactions emerged. Trial effects were observed, with SJ improving 2.31 cm (p < 0.001) and CMJ 1.05 cm (p = 0.014) from first to second attempts, suggesting warm-up or neuromuscular potentiation. High intraclass correlation coefficients (ICC = 0.76-0.85) underscored substantial interindividual variability. Models demonstrated robust fit (conditional R2 = 0.86-0.92), with sufficient power to detect medium-to-large effects (f ≥ 0.25).

A 5 mg/kg caffeine dose, compliant with NCAA thresholds, did not enhance vertical jump performance in habituated collegiate athletes, challenging prior assertions of its universal ergogenicity for ballistic tasks. While sex differences in baseline performance persisted, caffeine did not modulate these disparities, implicating neuromuscular and anthropometric factors as primary determinants. The absence of ergogenic effects aligns with NCAA safety-focused policies but highlights the need for personalized dosing strategies and research into higher doses, genetic variability, and hormonal influences. Future studies should integrate biomechanical metrics and controlled hormonal assessments to elucidate caffeine's nuanced role in anaerobic power sports.

As dietary supplements play a crucial role in meeting the unique nutritional needs of soccer players, a growing body of studies are exploring the effects of dietary supplements on athletic performance in soccer players. The effectiveness of certain supplements, such as caffeine and creatine, remains debated due to inconsistent results across studies. Therefore, this systematic review and Bayesian network meta-analysis was conducted to tentatively identify the most effective dietary supplements for soccer players.

We searched PubMed, Web of Science, Cochrane, Embase, and SPORTDiscus from database establishment to 5 February 2024 to identify randomized controlled trials (RCTs) evaluating the effects of different dietary supplements on athletic performance in soccer players. The risk of bias was assessed using the revised Cochrane risk-of-bias tool for randomized trials. A Bayesian network meta-analysis was performed using the R software and Stata 18.0. A subgroup analysis was conducted based on the competitive level of the athletes.

Eighty RCTs were included, with 1,425 soccer players randomly receiving 31 different dietary supplements or placebo. The network meta-analysis showed that compared with placebo, carbohydrate + protein (SMD: 2.2, very large), carbohydrate + electrolyte (SMD: 1.3, large), bovine colostrum (SMD: moderate) and caffeine (SMD: 0.29, small) were associated with a significant effect on increasing the distance covered. Kaempferia parviflora (SMD: 0.46, small) was associated with a significant effect on enhancing muscular strength. Beta-alanine (SMD: 0.83, moderate), melatonin (SMD: 0.75, moderate), caffeine (SMD: 0.37, small), and creatine (SMD: 0.33, small) were associated with a significant effect on enhancing jump height. Magnesium creatine chelate (SMD: -3.0, very large), melatonin (SMD: -1.9, large), creatine + sodium bicarbonate (SMD: -1.4, large), and arginine (SMD: -1.2, moderate) were associated with a significant effect on decreasing sprint time. Creatine + sodium bicarbonate (SMD: -2.3, very large) and caffeine (SMD: -0.38, small) were associated with a significant effect on improving agility. Sodium pyruvate (SMD: 0.50, small) was associated with a significant effect on increasing peak power. Magnesium creatine chelate (SMD: 1.3, large) and sodium pyruvate (SMD: 0.56, small) were associated with a significant effect on increasing mean power. Carbohydrate + electrolyte (SMD: -0.56, small) was associated with a significant effect on improving the rating of perceived exertion.

This study suggests that a range of dietary supplements, including caffeine, creatine, creatine + sodium bicarbonate, magnesium creatine chelate, carbohydrate + electrolyte, carbohydrate + protein, arginine, beta-alanine, bovine colostrum, Kaempferia parviflora, melatonin, and sodium pyruvate, can improve athletic performance in soccer players. This review provides evidence-based guidance for soccer coaches and nutritionists on using dietary supplements to enhance specific performance measures.

Background: Caffeine has become the psychostimulant with the highest use worldwide by different segments of the population. This is mainly due to the wide variety of benefits it offers in different contexts of use. It is available in various forms, with caffeine chewing gum recently generating great interest due to its characteristics and absorption time. Methods: A placebo-controlled study was conducted in which 20 healthy university students were exposed to three different conditions (single dose, partial dose, and placebo). The intervention consisted of a dual task in which heart rate, perceived exertion, and reaction time were monitored using the Stroop test and choice reaction time test while participants performed two blocks of cycloergometer exercise. Results: A t-test comparison between blocks showed differences in the Stroop test under all conditions, with the single dose having the best performance (Gr.A p < 0.001; Gr.B p < 0.029; Gr.C p < 0.009). The single dose group also showed favorable results for the HR/RPE ratio (p < 0.044) and an increase in the rate of perceived exertion (p < 0.006). No changes in reaction time were observed under any condition of the choice reaction time test. Conclusions: These results suggest that caffeine supplementation has positive effects on variables related to psychophysiological performance during a dual task. A single dose showed the best results in this study; however, longer intervention designs could be considered in the future to see the effect of partial doses of caffeine over time.

Despite the progress toward gender equality in events like the Olympic Games and other institutionalized competitions, and the rising number of women engaging in physical exercise programs, scientific studies focused on establishing specific nutritional recommendations for female athletes and other physically active women are scarce.

This systematic review aimed to compile the scientific evidence available for addressing the question "What dietary strategies, including dietary and supplementation approaches, can improve sports performance, recovery, and health status in female athletes and other physically active women?"

The Pubmed, Web of Science, and Scopus databases were searched.

The review process involved a comprehensive search strategy using keywords connected by Boolean connectors. Data extracted from the selected studies included information on the number of participants and their characteristics related to sport practice, age, and menstrual function.

A total of 71 studies were included in this review: 17 focused on the analysis of dietary manipulation, and 54 focused on the effects of dietary supplementation. The total sample size was 1654 participants (32.5% categorized as competitive athletes, 30.7% as highly/moderately trained, and 37.2% as physically active/recreational athletes). The risk of bias was considered moderate, mainly for reasons such as a lack of access to the study protocol, insufficient description of how the hormonal phase during the menstrual cycle was controlled for, inadequate dietary control during the intervention, or a lack of blinding of the researchers.

Diets with high carbohydrate (CHO) content enhance performance in activities that induce muscle glycogen depletion. In addition, pre-exercise meals with a high glycemic index or rich in CHOs increase CHO metabolism. Ingestion of 5-6 protein meals interspersed throughout the day, with each intake exceeding 25 g of protein favors anabolism of muscle proteins. Dietary supplements taken to enhance performance, such as caffeine, nitric oxide precursors, β-alanine, and certain sport foods supplements (such as CHOs, proteins, or their combination, and micronutrients in cases of nutritional deficiencies), may positively influence sports performance and/or the health status of female athletes and other physically active women.

PROSPERO registration no. CRD480674.

This study investigated the effects of combined Rhodiola rosea (RHO) and caffeine (CAF) supplementation on lower limb explosive power and fatigue recovery in volleyball players, aiming to validate their potential synergistic effects.

A randomized, double-blind, placebo-controlled design was implemented involving 48 male volleyball athletes allocated into four groups: placebo (CTR), Rhodiola rosea (RHO), caffeine (CAF), and combined (RHO + CAF). Over four weeks, participants engaged in twice-weekly high-intensity lower limb resistance training, with performance evaluated through multiple tests, including two-step-approach jump height, countermovement jump (CMJ), five-jump test (5 JT), continuous 20 vertical jumps, and intermittent jump recovery alongside Rate of Perceived Exertion (RPE) assessments.

Results showed that the combined supplementation (RHO + CAF) group exhibited significant improvement across multiple performance metrics. In particular, the combined group demonstrated the highest increases in jump height and the least power decline during high-frequency jumps, outperforming the CTR and other supplementation groups (p < 0.05). Additionally, RHO + CAF supplementation significantly lowered RPE scores, particularly in the final week of training, indicating improved perceived fatigue and recovery.

This study suggests that combining RHO and CAF optimizes high-intensity performance by enhancing explosive power, reducing fatigue, and improving recovery, presenting an effective nutritional strategy for volleyball athletes.

Modern elite football places extremely high demands on the athlete's body, so it is of practical interest to study the effect of various dietary supplements on load tolerance and postexercise recovery. Furthermore, there is a lack of research on the effects of caffeine on key measures of load tolerance in football such as delayed-onset muscle soreness (DOMS), rate of perceived exertion (RPE) and heart rate (HR) at different time points after the exercise.

54 young players aged 15-17 years from a leading Russian football academy took part in a randomised trial using the balanced placebo design. They were divided into 4 groups: 1 - told caffeine/given caffeine, 2 - told caffeine/given placebo, 3 - told placebo/given placebo and 4 - told placebo/given caffeine. All participants consumed two capsules 60 min before testing, each containing 200 mg of caffeine or placebo. Sprinting, counter-movement jump, change of direction run, dribbling, T-test and the repeated sprint ability test were used to create conditions for high-intensity sports-specific load. A visual analogue scale was used to assess the severity of muscle soreness. RPE was assessed using the Borg Rating of Perceived Exertion scale. HR immediately postexercise (HRpe), HR after 2 min of passive rest (HRrest) and recovery HR (HRrec = HRpe - HRrest) were obtained.

The data demonstrated that a single caffeine intake of 400 mg had no statistically significant effect on RPE (p = 0.948), HRpe (p = 0.698) or HRrec (p = 0.920) across the groups. Additionally, the severity of DOMS 24 h postexercise did not differ significantly between the groups (p = 0.077).

Acute caffeine ingestion does not affect the subjective and objective indicators of training load in young football players aged 15-17 years with low levels of anxiety and low levels of daily caffeine intake.

Energy drinks are a commonly consumed beverage, and studies suggest a possible performance-enhancing effect. A Google Scholar search using the keywords "energy drinks" and "exercise" yields numerous results, underscoring the voluminous research on this topic. However, there are questions regarding the effectiveness and safety of energy drinks. These questions include, but are not limited to: (1) What are the main active ingredients in energy drinks? (2) Do energy drinks assist in weight management? (3) Do energy drinks enhance aerobic performance? (4) Do energy drinks enhance athletic speed? (5) Do energy drinks improve reaction time? (6) Do energy drinks enhance lean tissue mass? (7) Can energy drinks improve cognitive performance? (8) Does the acute consumption of energy drinks elevate resting energy expenditure? (9) Is there any evidence to suggest that energy drinks are more effective than an identical serving of caffeine alone? (10) Are there sex differences in the response to energy drink consumption? (11) Do energy drinks affect sleep or sleepiness? (12) Should pregnant women avoid energy drinks? (13) Do energy drinks adversely affect cardiovascular function? (14) Does consuming energy drinks cause brain damage? (15) What are other safety considerations regarding energy drinks? (16) Is there any evidence to suggest that energy drinks are more effective than an identical serving of caffeine alone? (17) If caffeine is the main active ingredient in energy drinks and coffee, why is there a discrepancy in the adverse events reported for each? To address these questions, we performed an evidence-based scientific evaluation of the literature on energy drink supplementation.

The purpose of the review was to evaluate the literature exploring nutritional habits and practices in female soccer players.

The PRISMA-ScR Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews were followed. Searches of Web of Science, PubMed and Scopus databases were conducted for studies exploring the nutritional habits and practices of female soccer players.

A total of 72 studies were included in the scoping review. Studies on female soccer players mainly focused on daily energy expenditure, daily energy and macronutrient intake and hydration status. A negative energy balance was consistent across studies, and the ingestion of CHO appears below the current recommendations. Female soccer players are predominately in negative energy balance, which may indicate that they are at risk of low energy availability. A high use of nutritional supplements is apparent in female soccer, whilst a large proportion of players commence training dehydrated.

The current findings have implications for practitioners relating to the planning, management, monitoring, and implementation of nutritional intake and training and competition schedules.

Caffeine is one of the most popular ergogenic aids consumed by athletes. Caffeine's ergogenic effect has been generally explained by its ability to bind to adenosine receptors, thus modulating pain and reducing perceived exertion. Another pharmacological agent that may improve performance due to its analgesic proprieties is paracetamol. This study aimed to explore the effects of caffeine, paracetamol, and caffeine + paracetamol consumption on muscular endurance, strength, power, anaerobic endurance, and jumping performance.

In this randomized, crossover, double-blind study, 29 resistance-trained participants (11 men and 18 women) ingested either a placebo, caffeine (3 mg/kg), paracetamol (1500 mg) or caffeine + paracetamol 45 min before the testing sessions. The testing sessions included performing the bench press exercise with 75% of one-repetition maximum to momentary muscular failure, isokinetic knee extension and flexion at angular velocities of 60°/sec and 180°/sec, Wingate, and countermovement jump (CMJ) tests.

Compared to placebo, isolated caffeine ingestion increased the number of repetitions performed in the bench press (p = 0.005; d = 0.42). Compared to placebo, isolated caffeine ingestion and/or caffeine + paracetamol consumption was ergogenic for strength (torque), muscular endurance (total work), or power in the isokinetic assessment, particularly at slower angular velocities (p = 0.027 to 0.002; d = 0.16 to 0.26). No significant differences between the conditions were observed for outcomes related to the Wingate and CMJ tests.

This study provided novel evidence into the effectiveness of caffeine, paracetamol, and their combination on exercise performance. We found improvements in muscular endurance, strength, or power only when caffeine was consumed in isolation, or in combination with paracetamol. Isolated paracetamol consumption did not improve performance for any of the analyzed outcomes, thus calling into question its ergogenic potential.

The benefits of oral caffeine intake to enhance several aspects of physical performance, such as aerobic endurance, strength, power, and muscle endurance performance, are well supported. However, how the physical performance benefits of caffeine supplementation are translated into better specific actions in intermittent sports during real or simulated competition has been the topic of fewer investigations, and their results need to be appropriately reviewed and meta-analyzed.

The aim of the study was to investigate the effects of acute caffeine intake on specific actions in intermittent sports involving decision making and high-intensity efforts (eg, team, racket, and combat sports) during real or simulated competitions.

All studies included had blinded and crossover experimental designs, and we conducted a risk-of-bias analysis. In total, we included 24 studies. A meta-analysis was performed using the random-effects model to calculate the standardized mean difference (SMD) estimated by Hedges g and 95% CIs.

Caffeine ingestion increased high-intensity sport-specific actions during competition, such as the number of sprints (SMD: 0.48; 95% CI, 0.23-0.74), body impacts (SMD: 0.28; 95% CI, 0.08-0.49), accelerations (SMD: 0.35; 95% CI, 0.06-0.63), decelerations (SMD: 0.63; 95% CI, 0.12-1.14), and high-intensity offensive efforts (SMD: 0.36; 95% CI, 0.11-0.61). Additionally, caffeine ingestion induced a higher positive or success rate of actions during real or simulated competition (SMD: 0.44; 95% CI, 0.19-0.69).

The current meta-analysis provides evidence of caffeine supplementation in increasing high-intensity efforts and the success rate of sport-specific actions during real or simulated competition.

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.

Caffeine is a widely used ergogenic aid in society, which has made it a topic of interest due to its various benefits at cognitive, physiological, and sports levels, among others. This review aims to investigate the potential benefits of caffeine supplementation in psychophysiological performance through a structured search in the SportsDiscus/Scopus/MEDLINE and Web of Science databases (October 2022). This review followed the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guideline, and the inclusion criteria were defined based on the PICOS model. Double-blind, randomized/semi-randomized crossover articles comparing caffeine intake with an identical placebo condition were included. Filters by age or gender of the participants were not applied. The initial search gave a result of 201 articles, which after eliminating duplicates and applying the inclusion and exclusion criteria, the final sample for this review was 8 studies. The review concluded that 3 (37.5 %) found favorable ergogenic effects, 4 (50 %) found partial effects, and 1 (12.5 %) found no effects of caffeine supplementation on variables related to psychophysiological performance. In general, both partial and negative results could be linked to insufficient doses to produce any change, likewise, habitual caffeine consumption is also a variable that could be attenuating its potential ergogenic effect. In conclusion, moderate doses of caffeine 3-6 mg/kg seem to be an effective strategy to improve the psychophysiological response in various contexts without generating detrimental effects on performance, as long as the intervention designs consider the variables that could condition its effect.

The present study aimed to investigate the effect of the timing of the last meal, "Suhoor", on diurnal variation in cognitive performance during Ramadan intermittent fasting (RIF). In a randomized order, 26 adolescent female athletes (aged 15.9 ± 0.9 y) were tested in three sessions at 7:00 a.m., 12:00 p.m., and 5:00 p.m. across four different conditions: the 10 days preceding Ramadan (PR); the final 12 days of Ramadan (RO): two different conditions: Early Suhoor (SEarly), and Late Suhoor (SLate); and, ultimately, the 10 days immediately after Ramadan (AR) with an in-between recovery period of ≥24 h. During each test session, the oral temperature (OT), simple reaction time test (SRT), choice reaction time test (CRT), attention test (ATT), and mental rotation test (MRT) were evaluated. The Pittsburgh Sleep Quality Index (PSQI) and daily diary intake were assessed across the three periods. Compared to PR, the sleep parameters assessed by the PSQI were significantly lower during the RO and AR periods. However, neither total dietary intake nor OT showed any changes due to RIF. Compared to PR, the afternoon performances of SRT, CRT, ATT, and MRT significantly declined under both the SEarly and SLate conditions. Notably, midday performance decreased only during SLate, while morning performance remained unaffected in both conditions. Additionally, compared to SEarly, these performances were better during SLate in the afternoon and at midday. In summary, nutrient intake timing had a significant effect on the diurnal fluctuations in cognitive functions during Ramadan fasting, particularly around noon and in the afternoon. Our results illustrate the benefits of a late last meal (Suhoor) in preserving optimal morning cognitive abilities and preventing any impairment during the fasted state at midday or in the afternoon, which could affect overall athletic performance.

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 present study aimed to 1) investigate the consumption of Sports Supplements (SSs) among female elite football players, 2) evaluate the influence of age on SS consumption, and 3) determine the relationship between the consumption of SSs and dietary choices among elite football players.

A total of 126 female football players of Primera Iberdrola and Reto Iberdrola who participated in this descriptive, observational, and cross-sectional study completed a self-administered questionnaire on SSs and the Athletes' Food Choices Questionnaire.

Overall, 84.1% of participants consumed supplements, mainly for improved sports performance (68.3%) and health (34.1%). The main sources of purchase were the Internet (34.9%) and specialized shops (23.8%), and players were commonly advised by a dietitian-nutritionist to use SSs (56.3%). The SSs most often consumed included whey protein (30.2%), sports drinks (28.6%), creatine monohydrate (28.6%), sports bars (27.8%), and caffeine (27.8%). Older players consumed more supplements at the time of data compilation. Players predominantly acquired these supplements by using the Internet and reported benefits from their use (all P ≤ 0.036). Additionally, players who consumed SSs conveyed more concern about their food choices.

A high prevalence of female football players consumed SSs, particularly SSs supported by robust scientific evidence. Older players had higher supplement consumption rates. The use of SSs was related to food choices through nutritional characteristics of foods, knowledge about health and nutrition, weight control with the help of food, and the performance benefits players could acquire.

Post-activation performance enhancement (PAPE) is a physiological phenomenon that refers to an acute excitation of the neuromuscular system following intense exercise that ends in enhanced physical performance in a subsequent bout of exercise. The scientific literature has primarily examined the effectiveness of PAPE alone or combined with caffeine (CAF) intake in all-out tests lasting ≤10 s, as the effect of PAPE is transitory. The aim of the present study was to determine the effect of a protocol to induce PAPE alone or in combination with caffeine intake on the 30 s Wingate Anaerobic Test in highly trained boxers. Twenty-five male and highly trained boxers (mean age: 20 ± 1 years) participated in a double-blind, randomized crossover study consisting of three different experimental conditions: (i) control (CON), with no substance intake and no PAPE protocol before the Wingate Anaerobic Test; (ii) PAPE + PLA, involving the intake of a placebo 60 min before and a PAPE protocol comprising a 10 s cycling sprint overloaded with 8.5% of the participants' body weight 10 min before the Wingate Anaerobic Test; and (iii) PAPE + CAF, involving the intake of 3 mg/kg of caffeine 60 min before and the same PAPE protocol used in the (ii) protocol before the Wingate Anaerobic Test. In all conditions, the participants performed the 30 s version of the Wingate Anaerobic Test with a load equivalent to 7.5% of their body weight, while the cycle ergometer setting was replicated. Immediately following the Wingate test, heart rate (HR), the rating of perceived exertion (RPE), and blood lactate concentration (Bla) were measured. In comparison to CON, PAPE + PLA enhanced mean power (p = 0.024; Effect size [ES] = 0.37) and total work (p = 0.022; ES = 0.38) during the Wingate test, accompanied by an increase in post-test blood lactate concentration (p < 0.01; ES = 0.83). In comparison to CON, PAPE + CAF enhanced mean power (p = 0.001; ES = 0.57), peak power (p = 0.013; ES = 0.57), total work (p = 0.001; ES = 0.53), post-test blood lactate concentration (p < 0.001; ES = 1.43) and participants' subjective perception of power (p = 0.041). There were no differences in any variable between PAPE + PLA and PAPE + CAF. In summary, a PAPE protocol that involves a 10 s all-out sprint 10 min before the Wingate Anaerobic Test was effective in enhancing Wingate mean power in highly trained boxers. The addition of 3 mg/kg of caffeine to the PAPE protocol produced an effect on mean power of a higher magnitude than PAPE alone, and it enhanced peak power along with participants' subjective perception of power. From a practical point of view, PAPE before exercise seems to be an effective approach for increasing Wingate performance in highly trained boxers, while the addition of caffeine can increase some benefits, especially peak power.

We aimed to perform a systematic review and meta-analysis of caffeine's effects on vertical jumping performance in females, with subgroup analyses for potential moderators, including phase of the menstrual cycle, testing time of day, caffeine dose, and test type. Fifteen studies were included in the review (n = 197). Their data were pooled in a random-effects meta-analysis of effect sizes (Hedges' g). In the main meta-analysis, we found an ergogenic effect of caffeine on jumping performance (g: 0.28). An ergogenic effect of caffeine on jumping performance was found when the testing was carried out in the luteal phase (g: 0.24), follicular phase (g: 0.52), luteal or follicular phase (g: 0.31), and when the phase was not specified (g: 0.21). The test for subgroup differences indicated that the ergogenic effects of caffeine were significantly greater in the follicular phase compared to all other conditions. An ergogenic effect of caffeine on jumping performance was found when the testing was carried out in the morning (g: 0.38), evening (g: 0.19), mixed morning or evening (g: 0.38), and when time was not specified (g: 0.32), with no subgroup differences. An ergogenic effect of caffeine on jumping performance was found when the dose was ≤3 mg/kg (g: 0.21), or >3 mg/kg (g: 0.37), with no subgroup differences. An ergogenic effect of caffeine on jumping performance was found in the countermovement jump test (g: 0.26) and squat jump test (g: 0.35), with no subgroup differences. In summary, caffeine ingestion is ergogenic for vertical jumping performance in females, and it seems that the magnitude of these effects is the largest in the follicular phase of the menstrual cycle.

The aim of this study was to investigate the ergogenicity of BioSteel High Performance Sports Drink (B-HPSD), a commercially available branched chain amino acid (BCAA) and vitamin B-6 (VitB-6) supplement, on multiple sprint exercise (MSE).

Eleven experienced cyclists completed two MSE trials in counterbalanced order, after ingesting either B-HPSD (2,256 mg of BCAA, 300 mcg of VitB-6) or placebo (PLA). The MSE protocol consisted of five maximal effort 1 km sprints on a cycle ergometer separated by 2 min of active recovery. Power output (PO) was continuously measured throughout the cycling protocol. Heart rate (HR) and ratings of perceived exertion (RPE) were monitored following each sprint. Capillary blood samples were collected and analyzed for lactate and glucose before and 2 min post-trial. Cognitive function was assessed before and 15 min after the exercise protocol.

The PO maintained during each 1 km sprint decreased throughout the protocol (p < 0.05), but the change in PO was similar between conditions. Post-exercise blood glucose was elevated after consuming B-HPSD but not PLA (p < 0.05). Blood lactate (p < 0.05), HR (p < 0.05) and RPE (p < 0.05) increased throughout the trials, however no differences were observed between conditions. Cognitive performance improved after exercise (p < 0.05), but the change was similar between conditions.

These results demonstrate that acute B-HPSD consumption does not have an ergogenic effect on MSE performance. However, ingestion of B-HPSD increased post-exercise blood glucose concentration when compared to PLA.

Dietary supplements are widely used among athletes, and soccer players are no exception. Nevertheless, evidence supporting the use of dietary supplements aiming to enhance performance in soccer is somewhat contradictory, scarce, or even nonexistent. Thus, the present study aimed to systematically review and synthesize the effects of dietary supplements on athletic performance (e.g. distance covered, sprinting, jump performance) in elite soccer players. Studies enrolling highly trained, elite, and world-class soccer players using dietary supplements were searched in MEDLINE/PubMed, Web of Science, Scopus, and EBSCO databases in June 2022. In total, 1043 studies were identified, and 18 met the eligibility criteria. The studies evaluated the impacts on athletic performance of several dietary supplements, including caffeine, creatine, protein, beverages with carbohydrates and electrolytes, tart cherry juice, nitrate-rich beetroot juice, sodium bicarbonate with minerals, yohimbine, and a proprietary nutraceutical blend. Caffeine supplementation in doses between 3 and 6 mg/kg of body mass may improve jump height and sprint ability, particularly in female players, but individual response to caffeine must be considered. Creatine may improve sprint, agility, and in female players, jump performance. Protein supplementation can improve sprint and jump performance between matches, especially if protein ingested from food is not up to recommendations. Beverages containing carbohydrates and electrolytes can be used as part of the strategies to achieve carbohydrate intake during training and match-days but used alone do not benefit athletic performance. Tart cherry juice might be useful for maintaining athletic performance after matches that produce higher force loss and exercise-induced muscle damage, although polyphenols from the diet might attenuate the effects of tart cherry supplementation. Nitrate-rich beetroot concentrate can attenuate performance decrease in the days following matches. Further investigation with sodium bicarbonate alone is necessary, as supplementation protocols with elite players included other substances. Finally, the available data does not support yohimbine supplementation or the use of Resurgex Plus® to improve athletic performance in elite soccer players. Still, more well-designed research with elite soccer players is needed to improve support and advice regarding the use of dietary supplements for athletic performance enhancement.

Position Statement: The International Society of Sports Nutrition (ISSN) bases the following position stand on a critical analysis of the literature regarding the effects of energy drink (ED) or energy shot (ES) consumption on acute exercise performance, metabolism, and cognition, along with synergistic exercise-related performance outcomes and training adaptations. The following 13 points constitute the consensus of the Society and have been approved by the Research Committee of the Society: Energy drinks (ED) commonly contain caffeine, taurine, ginseng, guarana, carnitine, choline, B vitamins (vitamins B1, B2, B3, B5, B6, B9, and B12), vitamin C, vitamin A (beta carotene), vitamin D, electrolytes (sodium, potassium, magnesium, and calcium), sugars (nutritive and non-nutritive sweeteners), tyrosine, and L-theanine, with prevalence for each ingredient ranging from 1.3 to 100%. Energy drinks can enhance acute aerobic exercise performance, largely influenced by the amount of caffeine (> 200 mg or >3 mg∙kg bodyweight [BW-1]) in the beverage. Although ED and ES contain several nutrients that are purported to affect mental and/or physical performance, the primary ergogenic nutrients in most ED and ES based on scientific evidence appear to be caffeine and/or the carbohydrate provision. The ergogenic value of caffeine on mental and physical performance has been well-established, but the potential additive benefits of other nutrients contained in ED and ES remains to be determined. Consuming ED and ES 10-60 minutes before exercise can improve mental focus, alertness, anaerobic performance, and/or endurance performance with doses >3 mg∙kg BW-1. Consuming ED and ES containing at least 3 mg∙kg BW-1 caffeine is most likely to benefit maximal lower-body power production. Consuming ED and ES can improve endurance, repeat sprint performance, and sport-specific tasks in the context of team sports. Many ED and ES contain numerous ingredients that either have not been studied or evaluated in combination with other nutrients contained in the ED or ES. For this reason, these products need to be studied to demonstrate efficacy of single- and multi-nutrient formulations for physical and cognitive performance as well as for safety. Limited evidence is available to suggest that consumption of low-calorie ED and ES during training and/or weight loss trials may provide ergogenic benefit and/or promote additional weight control, potentially through enhanced training capacity. However, ingestion of higher calorie ED may promote weight gain if the energy intake from consumption of ED is not carefully considered as part of the total daily energy intake. Individuals should consider the impact of regular coingestion of high glycemic index carbohydrates from ED and ES on metabolic health, blood glucose, and insulin levels. Adolescents (aged 12 through 18) should exercise caution and seek parental guidance when considering the consumption of ED and ES, particularly in excessive amounts (e.g. > 400 mg), as limited evidence is available regarding the safety of these products among this population. Additionally, ED and ES are not recommended for children (aged 2-12), those who are pregnant, trying to become pregnant, or breastfeeding and those who are sensitive to caffeine. Diabetics and individuals with preexisting cardiovascular, metabolic, hepatorenal, and/or neurologic disease who are taking medications that may be affected by high glycemic load foods, caffeine, and/or other stimulants should exercise caution and consult with their physician prior to consuming ED. The decision to consume ED or ES should be based upon the beverage's content of carbohydrate, caffeine, and other nutrients and a thorough understanding of the potential side effects. Indiscriminate use of ED or ES, especially if multiple servings per day are consumed or when consumed with other caffeinated beverages and/or foods, may lead to adverse effects. The purpose of this review is to provide an update to the position stand of the International Society of Sports Nutrition (ISSN) integrating current literature on ED and ES in exercise, sport, and medicine. The effects of consuming these beverages on acute exercise performance, metabolism, markers of clinical health, and cognition are addressed, as well as more chronic effects when evaluating ED/ES use with exercise-related training adaptions.

The aim of this investigation was to determine whether, after Ramadan, pre-exercise caffeine intake can reduce any possible negative effects of this month on short-term maximal performances in young female handball players. A randomized study involved thirteen young female handball players. Participants performed a squat jump (SJ), Illinois agility test (AG), and 5 m run shuttles test (total (TD) and peak (PD) distances) at 08:00 AM and 06:00 PM on three different occasions: one week before Ramadan (Pre-R), the last week of Ramadan (R), and the week after Ramadan (Post-R). A placebo (Pla) or caffeine (Caff) (6 mg·kg-1) was administered 60 min before exercise test sessions at two distinct times of day (08:00 AM and 06:00 PM) during the two periods: Pre and Post-R. The PSQI and dietary intake were assessed during all testing periods. The results revealed that Pre-R, (SJ, AG, TD, and PD) test performances were greater in the evening (PM) than in the morning (AM) (all p < 0.001). However, compared with Pre-R, PM performances declined significantly during R (all p < 0.001) and Post-R (p < 0.05, p < 0.01, p < 0.01 and p < 0.001, respectively). In addition, Pre-R, AM Caff produced moderate significant improvements compared with AM Pla, with small-to-no beneficial effects observed with PM Caff in SJ (4.8% vs. 1%), AG (1.8% vs. 0.8%), TD (2.8% vs. 0.3%), and PD (6% vs. 0.9%). Nevertheless, Caff produced moderate ergogenic effects during both AM and PM sessions during Post-R in SJ (4.4% vs. 2.4%), AG (1.7% vs. 1.5%), TD (2.9% vs. 1.3%), and PD (5.8% vs. 3%) with values approaching those of Pre-R Pla within the same time of day (p > 0.05, p > 0.05, p < 0.05, and p < 0.05, respectively). In summary, pre-exercise Caff intake with a dose equivalent to 6 mg·kg-1 reduced the negative effects of Ramadan fasting in several aspects of short-term maximal performances in young female handball players at both times of the day.

Soccer is a team sport that requires players to process a significant amount of information quickly and respond with both speed and accuracy to the ever-changing demands of the game. As such, success in soccer depends not only on physical attributes but also on cognitive abilities such as perception and decision-making. The aim of the current study was to investigate the acute effects of caffeine ingestion on Stroop test performance before and after repeated small-sided games (SSG) in professional soccer players. Twelve professional male soccer players (29 ± 4.1 years; 78.1 ± 7.7 kg body mass) participated in this study. A randomized crossover double-blind placebo-controlled trial was used. Caffeine (5 mg.kg^-1) or a placebo was ingested 45 min before a protocol consisting of five 5 min SSG with 1 min rest intervals. A computerized version of the colour Stroop test was completed immediately before and after the exercise protocol. During the Stroop test, words appeared on the computer screen in three different ways: (i) neutral words (neutral condition); (ii) correspondent colour (i.e., "red" painted in red; congruent condition), or; (iii) different colour (i.e., "red" painted in green; incongruent condition). The incongruent condition aimed to cause the interference effect, as the colour and the word did not match. Ratings of perceived exertion (RPE) were assessed after each SSG. RPE increased during the five sets of the SSG protocol (p < 0.001), without differences between the caffeine and placebo trials. The soccer-specific exercise protocol promoted a faster response during the Stroop test (two-way ANOVA main effect for SSG protocol: p < 0.05), with no differences in accuracy (p > 0.05). Caffeine ingestion resulted in slower reaction time during the Stroop test during the congruent and neutral trials but not during the incongruent trial (two-way ANOVA main effect for supplementation: p = 0.009, p = 0.045, and p = 0.071, respectively). Accuracy was lower in the caffeine trial in congruent and incongruent trials (p < 0.05 caffeine vs. placebo both on the pre- and post-SSG protocol). In conclusion, a soccer-specific exercise protocol improved the Stroop test performance in professional soccer players, but acute caffeine ingestion (5 mg.kg^-1) was detrimental.

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.

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.

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).

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.

Despite emerging evidence about the influence of energy drinks on the quality of athletes' performance, there is little information about their effects on exercise-induced damage markers after long-term activities. This study aimed to investigate the acute effects of hype energy drink (HED) to ameliorate liver and muscle damage enzymes and cardiovascular indices-induced by a soccer match. A total of 22 elite male soccer players (age 20.36 ± 1.91) were recruited. Participants performed two experimental conditions, separated by a 14-day washout period. They consumed 2 × 250 ml of HED or placebo for 5 d before the soccer match, on match day, and for 1-day post-match. Measurements of muscle (CK and LDH), and liver (ALT, AST, and ALP) damage indices, and blood pressure (BP) parameters were taken at baseline, pre-match, post-match, and 24 h post-match. The results showed that the levels of ALT, AST, ALP, CPK, and LDH enzymes significantly decreased in HED condition from pre-match to 24 h post-match, compared with placebo (p < 0.001). Also, consumption of energy drinks reduced systolic, diastolic, and mean BP. In conclusion, elevated serum levels of muscle and liver damage enzymes and higher values of BP indices are improved 24 hours after soccer match following HED ingestion, compared to placebo. Therefore, it seems that consuming HED can lead to faster recovery of muscle and liver damage and improve recovery in soccer players.

Contemporary top-division soccer is characterized by high-intensity activity throughout the entire match, which also requires high levels of a wide range of the players' functional and motor abilities. Furthermore, motor and functional requirements vary in relation to the players' position on the pitch. In view of the above, the objective of this study was to determine any differences in body composition and specific motor abilities in relation to position. Twenty elite female soccer players (age: 20.90 ± 3.70 years; height: 166.95 ± 5.83 cm; weight: 58.97 ± 7.50 kg; training experience: 9.50 ± 4.11 years) were recruited for the purpose of this study. Based on their position within the team, the players were divided into three groups: defenders (N-7), midfielders (N-6), and forwards (N-7). The instruments used included the InBody770 (for body composition assessment), Optojump and Polar for the assessment of specific motor abilities. The results obtained indicate a strong link between the parameters body composition and specific motor abilities; however, the level of significance varies, as do the variables concerning specific motor abilities and body composition in relation to the players' position on the pitch. In accordance with these results, coaches and others working in the soccer industry should be apprised of the necessity of a tailored approach when it comes to planning the development of specific motor abilities, as well of with the importance of balanced body composition as prerequisites for achieving top results.

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.

Most intervention studies investigating the effects of ergogenic aids (EAs) on sports performance have been carried out in the male population. Thus, the aim of this systematic review and meta-analysis was to summarize the effects in the existing literature of EAs used by female athletes on performance. A literature research was conducted, and a descriptive analysis of the articles included in the systematic review was carried out. Meta-analyses could be performed on 32 of the included articles, evaluating performance in strength, sprint, and cardiovascular capacity. A random-effects model and the standardized mean differences (SMD) ± 95% confidence intervals (CI) were reported. The results showed that caffeine helped to improve jumping performance, isometric strength values, and the number of repetitions until failure. Caffeine and sodium phosphate helped to improve sprint performance. Aerobic tests could be improved with the use of taurine, caffeine, and beta-alanine. No conclusive effects of beetroot juice, polyphenols, or creatine in improving aerobic performance were shown. In terms of anaerobic variables, both caffeine and sodium phosphate could help to improve repeated sprint ability. More studies are needed in female athletes that measure the effects of different EAs on sports performance, such as beetroot juice, beta-alanine or sodium phosphate, as the studies to date are scarce and there are many types of EA that need to be further considered in this population, such as creatine and taurine.

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

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.

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.

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.

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.

Caffeine improves cycling time trial (TT) performance; however, it is unknown whether caffeine is ergogenic when competing against other riders. The aim of this study was to investigate whether caffeine improves performance during a 4-km cycling TT when riding against a virtual opponent, and whether it is associated with increased muscle activation and at the expense of greater end-exercise central and peripheral fatigue.

Using a randomized, crossover, and double-blind design, eleven well-trained cyclists completed a 4-km cycling TT alone without supplementation (CON), or against a virtual opponent after ingestion of placebo (OP-PLA) or caffeine (5 mg^.kg^-1, OP-CAF). Central and peripheral fatigue were quantified via the pre- to post-exercise decrease in voluntary activation and potentiated twitch force, respectively. Muscle activation was continually measured during the trial via electromyography activity.

Compared to CON, OP-PLA improved 4-km cycling TT performance (P = 0.018), and OP-CAF further improved performance when compared to OP-PLA (P = 0.050). Muscle activation was higher in OP-PLA and OP-CAF than in CON throughout the trial (P = 0.003). The pre- to post-exercise reductions in voluntary activation and potentiated twitch force were, however, similar between experimental conditions (P > 0.05). Compared to CON, OP-PLA increased the rating of perceived exertion during the first 2 km, but caffeine blunted this increase with no difference between the OP-CAF and CON conditions.

Caffeine is ergogenic when riding against a virtual opponent, but this is not due to greater muscle activation or at the expense of greater end-exercise central or peripheral fatigue.

CAF: Caffeine PLC: Placebo SRT: Simple Reaction Time AT: Attention Test SJ: Squat Jump IAT: Illinois Agility Test OT: Oral Temperature QUEST: Questionnaire RPE: Rating of Perceived Exertion PD: Peak Distance TD: Total Distance.

Beetroot juice (BRJ) is used as an ergogenic aid, but no previous study has analyzed the effect this supplement has on the production of explosive force and muscular endurance in physically active women.

BRJ improves explosive force and muscular endurance in the lower limbs of physically active women.

Randomized double-blind crossover study.

Level 3.

Fourteen physically active women performed a countermovement jump (CMJ) test, a back squat test for assessing velocity and power at 50% and 75% of one-repetition maximum (1RM), and the number of repetitions on a muscular endurance test consisting of 3 sets at 75% of 1RM in a resistance training protocol comprising 3 exercises (back squat, leg press, and leg extension). The participants performed the test in 2 sessions, 150 minutes after ingesting 70 mL of either BRJ (400 mg of nitrate) or a placebo (PLA).

A greater maximum height was achieved in the CMJ after consuming BRJ compared with a PLA (P = 0.04; effect size (ES) = 0.34). After a BRJ supplement at 50% 1RM, a higher mean velocity [+6.7%; P = 0.03; (ES) = 0.39 (-0.40 to 1.17)], peak velocity (+6%; P = 0.04; ES = 0.39 [-0.40 to 1.17]), mean power (+7.3%; P = 0.02; ES = 0.30 [-0.48 to 1.08]) and peak power (+6%; P = 0.04; ES = 0.20 [-0.59 to 0.98]) were attained in the back squat test. In the muscular endurance test, BRJ increased performance compared with the PLA (P < 0.00; η_p² = 0.651).

BRJ supplements exert an ergogenic effect on the ability to produce explosive force and muscular endurance in the lower limbs in physically active women.

If physically active women took a BRJ supplement 120 minutes before resistance training their performance could be enhanced.

Beetroot juice (BJ) and caffeine (CAF) are considered as ergogenic aids among athletes to enhance performance, however, the ergogenic effects of BJ and CAF co-ingestion are unclear during team-sport-specific performance. This study aimed to investigate the acute effects of BJ and CAF co-ingestion on team-sport-specific performance, compared with placebo (PL), BJ, and CAF alone.

Sixteen semi-professional male soccer players (age: 19.8 ± 2.2 years, body mass: 69.2 ± 6.1 kg, height: 177.3 ± 6.0 cm) completed four experimental trials using a randomized, double-blind study design: BJ + CAF, CAF + PL, BJ + PL, and PL + PL. Countermovement jump with arm swing (CMJAS) performance and cognitive function by Stroop Word-Color test were evaluated before and after the Yo-Yo Intermittent Recovery Test level 1 (YYIR1). Also, rate of perceived exertion (RPE), heart rate, and gastrointestinal (GI) discomfort were measured during each session.

No significant differences were shown between test conditions for total distance covered in YYIR1 (BJ + CAF: 1858 ± 455 m, CAF + PL: 1798 ± 422 m, BJ + PL: 1845 ± 408 m, PL + PL 1740 ± 362 m; p = 0.55). Moreover, CMJAS performance, cognitive function, and RPE during the YYIR1 were not significantly different among conditions (p > 0.05). However, the average heart rate during the YYIR1 was higher in CAF + PL compared to PL + PL (by 6 ± 9 beats/min; p < 0.05), and GI distress was greater in BJ + CAF compared to PL + PL (by 2.4 ± 3.6 a.u.; p < 0.05).

These results suggest, neither acute co-ingestion of BJ + CAF nor BJ or CAF supplementation alone significantly affected team-sport-specific performance compared to the PL treatment.

Caffeine is a psycho-active stimulant that can improve physical and cognitive performance. We systematically reviewed the evidence on the effects of acute caffeine ingestion on physiological parameters, physical and technical-skill performance during high-performance team-sport match-play. Following PRISMA guidelines, studies were identified using scientific databases (PubMed, Web-of-Science, Scopus, and SPORTDiscus) in February 2021. Of 281 results, 13 studies met inclusion, totalling 213 participants. Included studies adopted the randomised double-blinded cross-over design, involving caffeine and control conditions. In studies reporting physiological variables, responses to caffeine included higher peak (n=6/ 8 [n/ total studies measuring the variable]) and mean (n=7/ 9) heart rates, increased blood glucose (n=2/ 2) and lactate (n=2/ 2) concentrations. Improvements in physical performance were widely documented with caffeine, including greater distance coverage (n=7/ 7), high-speed distance coverage (n=5/ 7) and impact frequencies (n=6/ 8). From three studies that assessed technical-skills, it appears caffeine may benefit gross-skill performance, but have no effect, or negatively confound finer technical-skill outcomes. There is compelling evidence that ingesting moderate caffeine doses (~3 to 6 mg·kg-1) ~60 minutes before exercise may improve physical performance in team-sports, whereas evidence is presently too scarce to draw confident conclusions regarding sport-specific skill performance.

Beta-alanine, caffeine, and nitrate are dietary supplements generally recognized by the sport and exercise science community as evidence-based ergogenic performance aids. Evidence supporting the efficacy of these supplements, however, is greatly skewed due to research being conducted primarily in men. The physiological differences between men and women, most notably in sex hormones and menstrual cycle fluctuations, make generalizing male data to the female athlete inappropriate, and potentially harmful to women. This narrative review outlines the studies conducted in women regarding the efficacy of beta-alanine, caffeine, and nitrate supplementation for performance enhancement. Only nine studies on beta-alanine, 15 on caffeine, and 10 on nitrate in healthy women under the age of 40 years conducted in normoxia conditions were identified as relevant to this research question. Evidence suggests that beta-alanine may lower the rate of perceived exertion and extend training bouts in women, leading to greater functional adaptations. Studies of caffeine in women suggest the physiological responder status and caffeine habituation may contribute to caffeine's efficacy, with a potential plateau in the dose-response relationship of performance enhancement. Nitrate appears to vary in influence based on activity type and primary muscle group examined. However, the results summarized in the limited literature for each of these three supplements provide no consensus on dosage, timing, or efficacy for women. Furthermore, the literature lacks considerations for hormonal status and its role in metabolism. This gap in sex-based knowledge necessitates further research on these ergogenic supplements in women with greater considerations for the effects of hormonal status.