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Coffee Consumption and Risk of Hypertension in Adults: Systematic Review and Meta-Analysis.
Haghighatdoost, F, Hajihashemi, P, de Sousa Romeiro, AM, Mohammadifard, N, Sarrafzadegan, N, de Oliveira, C, Silveira, EA
Nutrients. 2023;15(13)
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High blood pressure (hypertension) is the main risk factor for cardiovascular diseases. Over the past decades the number of people experiencing high blood pressure has steadily increased, making it a serious concern for public health. Many dietary factors influence the development of high blood pressure, either increasing of decreasing the risk. Coffee is a widely consumed beverage. The caffeine in coffee can stimulate stress hormones like adrenaline. Adrenaline increases blood pressure, inflammation and decreases sensitivity to insulin, which are all regarded as risk factors for cardiovascular diseases. At the same time coffee contains many blood pressure lowering nutrients and compounds. Whether coffee contributes or diminishes the risks of developing high blood pressure has remained controversial. Hence, this systematic review and meta-analysis aimed to summarise the current evidence on coffee and hypertension risk. The analysis included 25 observational studies published between 2002 and 2023. The results concluded that coffee consumption was associated with a small reduction in risk for high blood pressure development. An inverse association was found, suggesting that as coffee consumption rose, high blood pressure risk falls. However, upon closer examination this inverse relationship was only found in the USA, but not in Europe and Asia. The authors suggested that geographics, genetics, gender, coffee preparation methods, and differences in lifestyle habits (smoking, salt consumption etc.) may contribute to the discrepancies between outcomes and make it harder to compare studies to form a uniform consensus. Hence, they urged for a cautious interpretation of the findings. In the absence of clear, consistent evidence, coffee consumption and cardiovascular risk may need to be assessed on an individual basis in clinical practice.
Abstract
OBJECTIVES The association between coffee intake and hypertension (HTN) risk is controversial. Therefore, this systematic review and meta-analysis aimed at summarizing the current evidence on the association of coffee with hypertension risk in observational studies. METHODS PubMed/Medline and Web of Science were searched for observational studies up to February 2023. Observational studies which assessed the risk of HTN in the highest category of coffee consumption in comparison with the lowest intake were included in the current meta-analysis (registration number: CRD42022371494). The pooled effect of coffee on HTN was evaluated using a random-effects model. RESULTS Twenty-five studies i.e., thirteen cross-sectional studies and twelve cohorts were identified to be eligible. Combining 13 extracted effect sizes from cohort studies showed that higher coffee consumption was associated with 7% reduction in the risk of HTN (95% CI: 0.88, 0.97; I2: 22.3%), whereas combining 16 effect sizes from cross-sectional studies illustrated a greater reduction in HTN risk (RR = 0.79, 95% CI: 0.72, 0.87; I2 = 63.2%). These results varied by studies characteristics, such as the region of study, participants' sex, study quality, and sample size. CONCLUSIONS An inverse association was found between coffee consumption and hypertension risk in both cross-sectional and cohort studies. However, this association was dependent on studies characteristics. Further studies considering such factors are required to confirm the results of this study.
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Effects of dietary supplements on athletic performance in elite soccer players: a systematic review.
Abreu, R, Oliveira, CB, Costa, JA, Brito, J, Teixeira, VH
Journal of the International Society of Sports Nutrition. 2023;20(1):2236060
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Dietary supplements are used by elite soccer players to improve performance and recovery. However, it is unclear as to whether the research can back up the reasons for their use. This systematic review of 18 randomised control trials aimed to determine any effects of dietary supplements on elite, adult soccer players. The results showed that studies on the use of supplementation in soccer players has been completed using caffeine, caffeinated energy drinks, creatine, protein, beverages with carbohydrates and electrolytes, tart cherry juice, nitrate-rich beetroot juice, yohimbine, Resurgex Plus, and sodium and potassium bicarbonate with potassium, magnesium, and calcium citrate. It was concluded that the use of creatine, protein, and caffeine may be of benefit to the performance of elite soccer players. The use of yohimbine was strongly discouraged due to unclear safety data. There was a lack of evidence for the use of any of the other supplements and it was concluded that more studies need to be completed. This study could be used by healthcare professionals to understand that certain supplements may enhance athletic performance in elite soccer players, but more research is encouraged.
Abstract
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.
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Energy Drinks and Sleep among Adolescents.
Tomanic, M, Paunovic, K, Lackovic, M, Djurdjevic, K, Nestorovic, M, Jakovljevic, A, Markovic, M
Nutrients. 2022;14(18)
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Sleep deprivation is a common problem among adolescents. There has been an increase in the consumption of energy drinks among adolescents in recent years. It is well known that energy drinks contain caffeine, sugar, and amino acids such as taurine, B vitamins, Ginseng, and guarana, which have psychoactive properties and disrupt the circadian rhythm. Insufficient sleep can affect genes involved in circadian rhythm and serotonin pathways, resulting in a higher risk of developing mental health problems. Therefore, researchers accessed the data from a population-based cross-sectional study to evaluate the effect of an energy drink on sufficient sleep in male and female adolescents. This study found that high energy drink consumption negatively affected sufficient sleep in male and female adolescents, with boys consuming energy drinks more frequently. The intake of vegetables and water, as well as regular physical activity, were positively correlated with adequate sleep in male adolescents. Physical activity and sufficient sleep were positively correlated in girls. Girls who used sedatives were less likely to get sufficient sleep. In order to determine how the different ingredients of energy drinks affect the sleep quality and neurodevelopment of adolescents individually and synergistically, further robust studies are required. The results of this study may help healthcare professionals to understand the adverse effects of energy drinks on adolescents.
Abstract
Many adolescents worldwide have the problem of meeting recommended nightly sleep hours. The causes of sleep disturbance are multifactorial, but interest in food's effect on sleep has dramatically increased lately. In this study, we investigated the association between regular energy drink (ED) intake (weekly or more frequent) and sufficient sleep (SS) (≥8 h) in adolescents. Additional objectives were to examine the relationship between health-related behaviors and SS, stratified by gender. A population-based cross-sectional study was conducted during the 2019/2020 school year from 12 schools in Belgrade. There were 1287 students aged 15 to 19 who participated (37.4% male). We used a modified version of the food frequency questionnaire adapted for Serbian adolescents. Logistic regression revealed that regular ED consumption was an independent risk factor negatively related to SS in both sexes. Additionally, daily vegetable and water intake (≥2 L) showed a positive correlation with SS in boys, while in girls, the odds of realizing SS decreased with statements of sedative use. In conclusion, we show that ED intake is negatively associated with SS in both sexes; daily vegetable and water intake (≥2 L) may raise the odds of SS in boys, while sedative use may decrease the chances of SS in girls.
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Caffeine and attentional control: improved and impaired performance in healthy older adults and Parkinson's disease according to task demands.
Sharma, K, Fallon, SJ, Davis, T, Ankrett, S, Munro, G, Christopher, G, Coulthard, E
Psychopharmacology. 2022;239(2):605-619
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Impairments in goal-directed attention are a frequent problem in older adults but these problems become magnified in neurodegenerative conditions like Parkinson's disease (PD). Although symptomatic treatment of PD focuses on motor deficits, cognitive deficits can be disabling, even in the early stages. This study is a single-blind, cross-over trial which compared the effect of a tablet containing 100-mg caffeine (Proplus) which was dissolved in instant decaffeinated coffee. Twenty-four PD patients and forty-four aged matched healthy elderly participants (controls) were enrolled in the study. Results show that caffeine: - did not affect attention in a unitary manner, across all attentional networks. In fact, the effect of caffeine on cognitive performance depended greatly upon the specific task requirements. - improved accuracy on the choice reaction time task. - improved accuracy of response selection in both the congruent and incongruent conditions. Authors conclude that caffeine’s overall attentional effects put forward by their study should be considered neither exclusively positive nor detrimental but instead conditional on task demands.
Abstract
INTRODUCTION Caffeine is frequently consumed to boost goal-directed attention. These procognitive effects may occur due to the adenosine-mediated enhancement of monoamines, such as dopamine, after caffeine administration. As such, caffeine's beneficial effects may be altered in conditions such as Parkinson's disease (PD). However, whether caffeine improves cognition, and at what cost, has not been experimentally established in patients with neurodegenerative disease. METHODS Single-dose trials to probe cognitive effects of caffeine are often confounded by short-term caffeine abstinence which conflates caffeine's effects with treatment of withdrawal. Using a placebo controlled, blinded, randomised trial design, we assessed the effect of 100 mg of caffeine across well-established tasks (Choice reaction time, Stroop Task and Rapid Serial Visual Presentation Task; RSVP) that probe different aspects of attention in PD patients (n = 24) and controls (n = 44). Critically, participants withdrew from caffeine for a week prior to testing to eliminate the possibility that withdrawal reversal explained any cognitive benefit. RESULTS Caffeine administration was found to reduce the overall number of errors in patients and controls on the Stroop (p = .018, η2p = .086) and Choice reaction time (p < . 0001, η2p = .588) tasks, but there was no specific effect of caffeine on ignoring irrelevant information in the Stroop task. On the RSVP task, caffeine improved dual item accuracy (p = .037) but impaired single item accuracy (p = .044). Across all tasks, there was little evidence that caffeine has different effects in PD participants and controls. CONCLUSION When removing withdrawal effects as a factor, we demonstrate caffeine has beneficial effects on selective attention but is a double-edge sword for visual temporal attention and would need careful targeting to be clinically useful.
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Caffeinated Drinks and Physical Performance in Sport: A Systematic Review.
Jiménez, SL, Díaz-Lara, J, Pareja-Galeano, H, Del Coso, J
Nutrients. 2021;13(9)
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Caffeine is a well-documented ergogenic aid and is often consumed by athletes to enhance overall performance. While this is established, there is currently no clarification on whether the performance-enhancing effects of caffeine differ depending on the category of sport. The aim of this study is to assess the effects of caffeinated drinks in various categories including endurance, power-based, team, and skill-based sports. This review included 37 studies and found caffeinated drinks to be an effective tool for increasing several aspects of individual performance. These drinks were more beneficial during long-duration exercise when they served as both rehydration and caffeine supplementation, but played an ergogenic role in each of the sports categories included in this study. Based on the current literature, the authors conclude caffeinated drinks to be an effective supplementation for athletes. They also suggest practising caution when using these drinks to increase ahtletic performance as the potential side effects were not a focus of this particular review.
Abstract
Caffeine (1,3,7-trimethylxanthine) is one of the most common substances used by athletes to enhance their performance during competition. Evidence suggests that the performance-enhancing properties of caffeine can be obtained by employing several forms of administration, namely, capsules/tablets, caffeinated drinks (energy drinks and sports drinks), beverages (coffee), and chewing gum. However, caffeinated drinks have become the main form of caffeine administration in sport due to the wide presence of these products in the market. The objective of this systematic review is to evaluate the different effects of caffeinated drinks on physical performance in various sports categories such as endurance, power-based sports, team sports, and skill-based sports. A systematic review of published studies was performed on scientific databases for studies published from 2000 to 2020. All studies included had blinded and cross-over experimental designs, in which the ingestion of a caffeinated drink was compared to a placebo/control trial. The total number of studies included in this review was 37. The analysis of the included studies revealed that both sports drinks with caffeine and energy drinks were effective in increasing several aspects of sports performance when the amount of drink provides at least 3 mg of caffeine per kg of body mass. Due to their composition, caffeinated sports drinks seem to be more beneficial to consume during long-duration exercise, when the drinks are used for both rehydration and caffeine supplementation. Energy drinks may be more appropriate for providing caffeine before exercise. Lastly, the magnitude of the ergogenic benefits obtained with caffeinated drinks seems similar in women and men athletes. Overall, the current systematic review provides evidence of the efficacy of caffeinated drinks as a valid form for caffeine supplementation in sport.
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Ergogenic Effects of Acute Caffeine Intake on Muscular Endurance and Muscular Strength in Women: A Meta-Analysis.
Grgic, J, Del Coso, J
International journal of environmental research and public health. 2021;18(11)
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Caffeine is a well-documented ergogenic aid. Among the existing studies that have explored this topic, women are largely underrepresented in the data. The aim of this meta-analysis was to evaluate whether the ergogenic effects of caffeine on strength and endurance known to be true for men could also be extended to women. The analysis included studies that used women as participants and found caffeine to have a significant ergogenic effect on both endurance and strength. When a sub-group analysis differentiated between upper- and lower-body exercises independently, only upper-body performance was improved by caffeine ingestion. Based on the current literature, the authors conclude the ergogenic effects that were previously observed in men are also applicable to women. They suggest further investigation as to why the ergogenic effect differs between upper- and lower-body performance.
Abstract
This meta-analysis aimed to explore the effects of caffeine ingestion on muscular endurance and muscular strength in women. Five databases were searched to find relevant studies. A random-effects meta-analysis of standardized mean differences (SMD) was performed for data analysis. Subgroup meta-analyses explored the effects of caffeine on upper-body and lower-body muscular endurance and muscular strength. Eight crossover placebo-controlled studies were included in the review. In the main meta-analysis that considered data from all included studies, there was a significant ergogenic effect of caffeine on muscular endurance (SMD = 0.25; p = 0.027) and muscular strength (SMD = 0.18; p < 0.001). In a subgroup analysis that considered only upper-body exercises, there was a significant ergogenic effect of caffeine on muscular endurance (SMD = 0.20; p = 0.007) and muscular strength (SMD = 0.17; p < 0.001). In a subgroup analysis that considered only lower-body exercises, there was no significant difference between caffeine and placebo for muscular endurance (SMD = 0.43; p = 0.092) or muscular strength (SMD = 0.16; p = 0.109). The main finding of this meta-analysis is that caffeine ingestion has a significant ergogenic effect on muscular endurance and muscular strength in women. The effects reported in this analysis are similar to those previously observed in men and suggest that women may use caffeine supplementation as an ergogenic aid for muscular performance. Future research is needed to explore the effects of caffeine on lower-body muscular endurance and muscular strength in this population.
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The effects of different doses of caffeine on maximal strength and strength-endurance in women habituated to caffeine.
Filip-Stachnik, A, Wilk, M, Krzysztofik, M, Lulińska, E, Tufano, JJ, Zajac, A, Stastny, P, Del Coso, J
Journal of the International Society of Sports Nutrition. 2021;18(1):25
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Athletes commonly consume caffeinated drinks or supplements containing caffeine due to its ergogenic effect on performance. However, very few studies have investigated the effect of acute intake of caffeine on muscular performance in strength-trained women. This randomised, double-blinded, crossover trial examines the effect of acute intake of caffeine on maximal strength and local strength-endurance during the bench press exercise in women habituated to acute intake of caffeine. In this study, twenty-one healthy and strength-trained women were randomised to take 3 and 6 mg/kg/body mass acute caffeine intake. While both doses showed positive effects, this study also observed a dose-dependent (6 mg/kg body mass) significant increase in the response of acute intake of caffeine on maximal strength in women habituated to caffeine. The acute intake of caffeine at 6 mg/kg/body mass also increased the number of repetitions and time under tension during the bench press. The results of the study must be interpreted with caution due to a wide variation in caffeine habituation, resistance training levels, and strength exercise practices across the general population. Future robust studies are required to investigate this further. This study may help healthcare practitioners better understand the ergogenic effects of caffeine consumption in strength-trained habituated women.
Abstract
PURPOSE The main goal of this study was to assess the acute effects of 3 and 6 mg of caffeine intake per kg of body mass (b.m.) on maximal strength and strength-endurance in women habituated to caffeine. METHODS Twenty-one healthy resistance-trained female students (23.0 ± 0.9 years, body mass: 59.0 ± 6.6 kg), with a daily caffeine intake of 5.8 ± 2.6 mg/kg/b.m. participated in a randomized, crossover, double-blind design. Each participant performed three experimental sessions after ingesting either a placebo (PLAC) or 3 mg/kg/b.m. (CAF-3) and 6 mg/kg/b.m. (CAF-6) of caffeine. In each experimental session, the participants underwent a 1RM test and a strength-endurance test at 50 %1RM in the bench press exercise. Maximal load was measured in the 1RM test and the time under tension, number of preformed repetitions, power output and bar velocity were registered in the strength-endurance test. RESULTS The one-way ANOVA showed a main effect of caffeine on 1RM bench press performance (F = 14.74; p < 0.01). In comparison to the PLAC (40.48 ± 9.21 kg), CAF-3 (41.68 ± 8.98 kg; p = 0.01) and CAF-6 (42.98 ± 8.79 kg; p < 0.01) increased 1RM bench press test results. There was also a significant increase in 1RM for CAF-6 when compared to CAF-3 (p < 0.01). There was a main effect of caffeine on time under tension during the strength-endurance test (F = 13.09; p < 0.01). In comparison to the PLAC (53.52 ± 11.44 s), CAF-6 (61.76 ± 15.39 s; p < 0.01) significantly increased the time under tension during the maximal strength-endurance test. CONCLUSION An acute dose of 3-to-6 mg/kg/b.m. of caffeine improves maximum strength. However, these doses of caffeine had minimal ergogenic effect on strength-endurance performance in women habituated to caffeine.
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The Dose-Effects of Caffeine on Lower Body Maximal Strength, Muscular Endurance, and Rating of Perceived Exertion in Strength-Trained Females.
Jones, L, Johnstone, I, Day, C, Le Marquer, S, Hulton, AT
Nutrients. 2021;13(10)
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Caffeine is a common ingredient in tea, coffee, chocolate, soft drinks and multi-ingredient pre-workout supplements. It is believed to elicit an ergogenic effect that enhances athletic performance. However, only very few studies have examined the effect of caffeine on women who take contraceptive pills. The aim of this double-blind, randomised, counterbalanced, crossover trial was to investigate the ergogenic effect of pre-exercise caffeine supplementation on strength performance and muscular endurance in strength-trained females taking contraceptives. Fourteen women were randomised to consume doses of 3 and 6 mg·kg−1 body mass of caffeine supplement or placebo thirty minutes prior to the exercise. Caffeine supplementation at 3 and 6 mg·kg−1 body mass significantly improved muscular endurance and total strength. No significant difference was observed between the higher and lower doses of caffeine in improving performance, indicating that the lower dose can potentially provide the same benefit without the adverse effect of the higher dose. The low dose had a similar caffeine content to that of a large coffee latte from a coffee shop, suggesting beneficial effects could be achieved through coffee/latte consumption. Caution should be applied when extrapolating the findings for eumenorrheic females with different training statuses. Healthcare practitioners can, however, use the results of this study to understand the potential benefits of caffeine for strength-trained women using hormone contraception.
Abstract
Caffeine supplementation has shown to be an effective ergogenic aid enhancing athletic performance, although limited research within female populations exists. Therefore, the aim of the investigation was to assess the effect of pre-exercise caffeine supplementation on strength performance and muscular endurance in strength-trained females. In a double-blind, randomised, counterbalanced design, fourteen strength-trained females using hormonal contraception consumed either 3 or 6 mg·kg-1 BM of caffeine or placebo (PLA). Following supplementation, participants performed a one-repetition maximum (1RM) leg press and repetitions to failure (RF) at 60% of their 1RM. During the RF test, rating of perceived exertion (RPE) was recorded every five repetitions and total volume (TV) lifted was calculated. Repeated measures ANOVA revealed that RF (p = 0.010) and TV (p = 0.012) attained significance, with pairwise comparisons indicating a significant difference between 3 mg·kg-1 BM and placebo for RF (p = 0.014), with an effect size of 0.56, and for 6 mg·kg-1 BM (p = 0.036) compared to the placebo, with an effect size of 0.65. No further significance was observed for 1RM or for RPE, and no difference was observed between caffeine trials. Although no impact on lower body muscular strength was observed, doses of 3 and 6 mg·kg-1 BM of caffeine improved lower body muscular endurance in resistance-trained females, which may have a practical application for enhancing resistance training stimuli and improving competitive performance.
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High Dose of Caffeine Mouth Rinse Increases Resistance Training Performance in Men.
Karayigit, R, Koz, M, Sánchez-Gómez, A, Naderi, A, Yildirim, UC, Domínguez, R, Gur, F
Nutrients. 2021;13(11)
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Caffeine intake is popular among athletes for its ergogenic effects. This study investigates the effect of caffeine mouth rinsing on strength and muscular performance in resistance-trained men. Caffeine mouth rinsing may aid exercise performance without the adverse effects of high caffeine doses. In this randomised, double-blinded, counterbalanced, crossover trial, fourteen healthy, resistance-trained men were assigned to do mouth rinsing using 1% (250 mg) or 2% (500 mg) or 3% (750 mg) caffeine solution and placebo. In resistance-trained men, five seconds of mouth rinsing with high-dose caffeine solution (3%) significantly reduced the rating of perceived exertion and increased the muscular endurance response. However, caffeine mouth rinse did not affect bench press one-repetition maximum strength performance. The study was conducted on a small sample of very low habitual caffeine takers in a fasted state. Therefore, the results are not translatable to athletes who take high doses of caffeine. Therefore, further extensive, robust studies are warranted to demonstrate the ergogenic effects of caffeine mouth rinse on resistance-trained males. Healthcare practitioners can use the findings of this study to understand the effect of early morning high dose caffeine mouth rinse on muscular endurance performance.
Abstract
Caffeine mouth rinsing (CMR) has been shown to enhance exercise performance. However, no studies have analyzed the effects of different dosages of CMR on muscular performance. Therefore, the purpose of this study was to examine the effects of different dosages of CMR on strength (bench press 1 repetition maximum (1-RM)) and muscular endurance (60% of 1-RM repetitions to failure) in resistance-trained males. Fourteen resistance-trained males (age: 23 ± 2 years, height: 179 ± 3 cm, body mass: 83 ± 4 kg, BMI: 17 ± 2 kg/m2) completed four conditions in random order. The four conditions consisted of a mouth rinse with 25 mL solutions containing either 1% (250 mg) of CMR (low dose of CMR: LCMR), 2% (500 mg) of CMR (moderate dose of CMR: MCMR), 3% (750 mg) of CMR (high dose of CMR: HCMR) and sweetened water (placebo: PLA) for 5 s prior to a bench press strength and muscular endurance test. Maximal strength, muscular endurance, heart rate (HR) and ratings of perceived exertion (RPE) were recorded for each condition. There were no significant differences in strength (p = 0.30) and HR (p = 0.83) between conditions. HCMR significantly increased muscular endurance performance (p = 0.01) and decreased RPE values (p = 0.01). In conclusion, CMR did not affect bench press 1-RM strength performance, but muscular endurance responses to CMR seems to be dose-dependent.
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Caffeine Supplementation and Physical Performance, Muscle Damage and Perception of Fatigue in Soccer Players: A Systematic Review.
Mielgo-Ayuso, J, Calleja-Gonzalez, J, Del Coso, J, Urdampilleta, A, León-Guereño, P, Fernández-Lázaro, D
Nutrients. 2019;11(2)
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Ergogenic aids, supplements that improve athletic performance, have become increasingly important in the global soccer community. Caffeine has been shown to produce ergogenic effects in both endurance sports and sprint performance. Recent studies have investigated the impact of caffeine intake on soccer physical performance however no review has evaluated these studies. The purpose of this systematic review was to critically evaluate the effect of acute caffeine ingestion on soccer players’ physical performance, muscle damage and perceived fatigue. This review included 17 articles, 12 of which examine soccer-specific abilities and 5 of which examine muscle damage. Based on the existing literature, caffeine was found to have ergogenic effects on jump height, sprint ability, passing accuracy and running distances during a soccer game. Caffeine was found to produce no effect on exercise-induced muscle damage however more research is needed in this area. Based on these results, the authors conclude a moderate dose of caffeine (3-6 mg/kg) may enhance physical performance specific to soccer players.
Abstract
Soccer is a complex team sport and success in this discipline depends on different factors such as physical fitness, player technique and team tactics, among others. In the last few years, several studies have described the impact of caffeine intake on soccer physical performance, but the results of these investigations have not been properly reviewed and summarized. The main objective of this review was to evaluate critically the effectiveness of a moderate dose of caffeine on soccer physical performance. A structured search was carried out following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines in the Medline/PubMed and Web of Science databases from January 2007 to November 2018. The search included studies with a cross-over and randomized experimental design in which the intake of caffeine (either from caffeinated drinks or pills) was compared to an identical placebo situation. There were no filters applied to the soccer players' level, gender or age. This review included 17 articles that investigated the effects of caffeine on soccer-specific abilities (n = 12) or on muscle damage (n = 5). The review concluded that 5 investigations (100% of the number of investigations on this topic) had found ergogenic effects of caffeine on jump performance, 4 (100%) on repeated sprint ability and 2 (100%) on running distance during a simulated soccer game. However, only 1 investigation (25%) found as an effect of caffeine to increase serum markers of muscle damage, while no investigation reported an effect of caffeine to reduce perceived fatigue after soccer practice. In conclusion, a single and moderate dose of caffeine, ingested 5⁻60 min before a soccer practice, might produce valuable improvements in certain abilities related to enhanced soccer physical performance. However, caffeine does not seem to cause increased markers of muscle damage or changes in perceived exertion during soccer practice.