Effect of repeated caffeine ingestion on repeated exhaustive exercise endurance

Nutritional Compounds to Improve Post-Exercise Recovery

The metabolic and mechanical stresses associated with muscle-fatiguing exercise result in perturbations to bodily tissues that lead to exercise-induced muscle damage (EIMD), a state of fatigue involving oxidative stress and inflammation that is accompanied by muscle weakness, pain and a reduced ability to perform subsequent training sessions or competitions. This review collates evidence from previous research on a wide range of nutritional compounds that have the potential to speed up post-exercise recovery. We show that of the numerous compounds investigated thus far, only two-tart cherry and omega-3 fatty acids-are supported by substantial research evidence. Further studies are required to clarify the potential effects of other compounds presented here, many of which have been used since ancient times to treat conditions associated with inflammation and disease.

A time and a place: A framework for caffeine periodization throughout the sporting year

Caffeine is a well-established ergogenic aid, with its performance-enhancing effects demonstrated across a variety of sports and exercise types. As a result of these ergogenic properties, caffeine is widely used by athletes at all levels around both competition and training. Caffeine exerts its performance benefits through a variety of mechanisms, each of which may be of increased importance at a given stage of training or competition. Additionally, regular caffeine use may diminish the performance-enhancing effects of a subsequent dose of caffeine. Recently, interest in the concept of nutritional periodization has grown. Here we propose a framework for the periodization of caffeine through the sporting year, balancing its training and competition performance-enhancing effects, along with the need to mitigate any negative effects of habituation. Furthermore, the regular use of caffeine within training may support the development of positive beliefs toward caffeine by athletes-potentially serving to enhance future performance through placebo and expectancy mechanisms-as well as allowing for the optimization of individual athlete caffeine strategies. Although future work is required to validate some of the suggestions made, the framework proposed here represents a starting point for athletes to maximize caffeine's performance benefits across the sporting year.

Carbohydrate supplementation: a critical review of recent innovations

PURPOSE

To critically examine the research on novel supplements and strategies designed to enhance carbohydrate delivery and/or availability.

METHODS

Narrative review.

RESULTS

Available data would suggest that there are varying levels of effectiveness based on the supplement/supplementation strategy in question and mechanism of action. Novel carbohydrate supplements including multiple transportable carbohydrate (MTC), modified carbohydrate (MC), and hydrogels (HGEL) have been generally effective at modifying gastric emptying and/or intestinal absorption. Moreover, these effects often correlate with altered fuel utilization patterns and/or glycogen storage. Nevertheless, performance effects differ widely based on supplement and study design. MTC consistently enhances performance, but the magnitude of the effect is yet to be fully elucidated. MC and HGEL seem unlikely to be beneficial when compared to supplementation strategies that align with current sport nutrition recommendations. Combining carbohydrate with other ergogenic substances may, in some cases, result in additive or synergistic effects on metabolism and/or performance; however, data are often lacking and results vary based on the quantity, timing, and inter-individual responses to different treatments. Altering dietary carbohydrate intake likely influences absorption, oxidation, and and/or storage of acutely ingested carbohydrate, but how this affects the ergogenicity of carbohydrate is still mostly unknown.

CONCLUSIONS

In conclusion, novel carbohydrate supplements and strategies alter carbohydrate delivery through various mechanisms. However, more research is needed to determine if/when interventions are ergogenic based on different contexts, populations, and applications.

Caffeine and Exercise: What Next?

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

Effects of Caffeine Supplementation on Performance in Ball Games

Although a large body of evidence exists documenting the ergogenic properties of caffeine, most studies have focused on endurance performance. However, findings from endurance sports cannot be generalized to performance in ball games where, apart from having a high level of endurance, successful athletic performances require a combination of physiological, technical and cognitive capabilities. The purpose of this review was to critically evaluate studies that have examined the effect of a single dose of caffeine in isolation on one or more of the following performance measures: total distance, sprint performance, agility, vertical jump performance and accuracy in ball games. Searches of three major databases resulted in 19 studies (invasion games: 13; net-barrier games: 6) that evaluated the acute effects of caffeine on human participants, provided the caffeine dose administered, and included a ball games specific task or simulated match. Improvements in sprint performance were observed in 8 of 10 studies (80%), and vertical jump in 7 of 8 studies (88%). Equivocal results were reported for distance covered, agility and accuracy. Minor side effects were reported in 4 of 19 studies reviewed. Pre-exercise caffeine ingestion between 3.0 and 6.0 mg/kg of body mass appears to be a safe ergogenic aid for athletes in ball games. However, the efficacy of caffeine varies depending on various factors, including, but not limited to, the nature of the game, physical status and caffeine habituation. More research is warranted to clarify the effects of caffeine on performance measures unique to ball games, such as agility and accuracy. It is essential that athletes, coaches and practitioners evaluate the risk-benefit ratio of caffeine ingestion strategies on an individual case-by-case basis.

Caffeine effects on VO2max test outcomes investigated by a placebo perceived-as-caffeine design

BACKGROUND

Ergogenic effects of caffeine (CAF) ingestion have been observed in different cycling exercise modes, and have been associated with alterations in ratings of perceived exertion (RPE). However, there has been little investigation of maximal oxygen uptake (VO_2MAX) test outcomes.

AIM

This study aimed to verify whether CAF may reduce RPE, thereby improving maximal incremental test (MIT) outcomes such as VO_2MAX, time to exhaustion and peak power output (W_PEAK).

METHODS

Nine healthy individuals performed three MITs (25 W/min until exhaustion) in a random, counterbalanced fashion after ingestion of CAF, placebo perceived as caffeine (PLA), and no supplementation (baseline control). VO₂ was measured throughout the test, while RPE was rated according to overall and leg effort sensations. The power output corresponding to submaximal (RPE = 14 according to the 6-20 Borg scale) and maximal RPE was recorded for both overall (O-RPE₁₄ and O-RPE_MAX) and leg RPE (L-RPE₁₄ and L-RPE_MAX).

RESULTS

VO_2MAX did not change significantly between MITs; however, CAF and PLA increased time to exhaustion (↑ ∼18.7% and ∼17.1%, respectively; p < .05) and W_PEAK (↑ ∼13.0% and ∼11.8%, respectively; p < .05) when compared with control. When compared with control, CAF ingestion reduced submaximal and maximal overall and leg RPEs, the effect being greater in maximal (likely beneficial in O-RPE_MAX and L-RPE_MAX) than submaximal RPE (possibly beneficial in O-RPE₁₄ and L-RPE₁₄). Similar results were found when participants ingested PLA.

CONCLUSIONS

Compared with control, CAF and PLA improved MIT performance outcomes such as time to exhaustion and W_PEAK, without altering VO_2MAX values. CAF effects were attributed to placebo.

Improvements in Cycling but Not Handcycling 10 km Time Trial Performance in Habitual Caffeine Users

Caffeine supplementation during whole-/lower-body exercise is well-researched, yet evidence of its effect during upper-body exercise is equivocal. The current study explored the effects of caffeine on cycling/handcycling 10 km time trial (TT) performance in habitual caffeine users. Eleven recreationally trained males (mean (SD) age 24 (4) years, body mass 85.1 (14.6) kg, cycling/handcycling peak oxygen uptake (V·_peak) 42.9 (7.3)/27.6 (5.1) mL∙kg∙min⁻¹, 160 (168) mg/day caffeine consumption) completed two maximal incremental tests and two familiarization sessions. During four subsequent visits, participants cycled/handcycled for 30 min at 65% mode-specific V·_peak (preload) followed by a 10 km TT following the ingestion of 4 mg∙kg⁻¹ caffeine (CAF) or placebo (PLA). Caffeine significantly improved cycling (2.0 (2.0)%; 16:35 vs. 16:56 min; p = 0.033) but not handcycling (1.8 (3.0)%; 24:10 vs. 24:36 min; p = 0.153) TT performance compared to PLA. The improvement during cycling can be attributed to the increased power output during the first and last 2 km during CAF. Higher blood lactate concentration (Bla) was reported during CAF compared to PLA (p < 0.007) and was evident 5 min post-TT during cycling (11.2 ± 2.6 and 8.8 ± 3.2 mmol/L; p = 0.001) and handcycling (10.6 ± 2.5 and 9.2 ± 2.9 mmol/L; p = 0.006). Lower overall ratings of perceived exertion (RPE) were seen following CAF during the preload (p < 0.05) but not post-TT. Lower peripheral RPE were reported at 20 min during cycling and at 30 min during handcycling, and lower central RPE was seen at 30 min during cycling (p < 0.05). Caffeine improved cycling but not handcycling TT performance. The lack of improvement during handcycling may be due to the smaller active muscle mass, elevated (Bla) and/or participants’ training status.

Observed Dietary Practices of Recreational Ultraendurance Cyclists in the Heat

Dietary approaches for optimizing exercise performance have been debated in the literature for years. For endurance athletes, various position stands focus on recommendations for high-carbohydrate diets to maximize performance in events. However, theories of low-carbohydrate diets and their ability to provide more fuel may prove beneficial to ultraendurance athletes. Therefore, the purpose of this research was to observe the food and fluid consumption of successful recreational ultraendurance cyclists on the day before (ED-1), Event Day, and the day after (ED+1), a 162 km endurance event in a hot environment, and subsequently compare dietary intakes to recommendations and other observed dietary practices. Twenty men (age, 48 ± 8 years; mass, 85.1 ± 13.4 kg; height, 178.2 ± 7.4 cm) recorded all dietary items during ED-1, Event Day, and ED+1. Diet composition and the relationships between carbohydrate and caloric intake with finish time were examined. Results show athletes consumed a high-carbohydrate diet on ED-1 (384 g·d), Event Day (657 g·d), and ED+1 (329 g·d). However, there were no significant associations between carbohydrate (p > 0.05), or caloric intake (p > 0.05), and finish time. This study results great variation in diets of recreational endurance cyclists, although most consume within nationally recognized dietary recommendation ranges. Because there is great variation and lack of correlation with performance, these findings suggest that current high-carbohydrate dietary recommendations for general endurance athletes may not be sport specific or individualized enough for recreational ultraendurance cyclists, and that individualized dietary macronutrient composition manipulations may improve performance outcomes.

Performance outcomes and unwanted side effects associated with energy drinks

Energy drinks are increasingly popular among athletes and others. Advertising for these products typically features images conjuring great muscle power and endurance; however, the scientific literature provides sparse evidence for an ergogenic role of energy drinks. Although the composition of energy drinks varies, most contain caffeine; carbohydrates, amino acids, herbs, and vitamins are other typical ingredients. This report analyzes the effects of energy drink ingredients on prolonged submaximal (endurance) exercise as well as on short-term strength and power (neuromuscular performance). It also analyzes the effects of energy drink ingredients on the fluid and electrolyte deficit during prolonged exercise. In several studies, energy drinks have been found to improve endurance performance, although the effects could be attributable to the caffeine and/or carbohydrate content. In contrast, fewer studies find an ergogenic effect of energy drinks on muscle strength and power. The existing data suggest that the caffeine dose given in studies of energy drinks is insufficient to enhance neuromuscular performance. Finally, it is unclear if energy drinks are the optimal vehicle to deliver caffeine when high doses are needed to improve neuromuscular performance.

Effects of energy drink major bioactive compounds on the performance of young adults in fitness and cognitive tests: a randomized controlled trial

Background

The consumption of beverages containing caffeine and taurine before exercising has been associated with increased physical and psychological performances and has been promoted to support the emotional state and provide vitality to consumers. However, there are contradictory results on these issues, it is not clear the effect of every major compound in relation to the whole effect of the beverages and there is a lack in knowledge about their degree of safety for consumption.

Methods

This study used a double-blind, placebo controlled, randomized, crossover design. Fourteen male volunteer soldiers from the Colombian army performed different tests to measure their cardiorespiratory fitness (VO₂max and maximum heart rate), time to exhaustion, strength (isometric strength), power (vertical jump), concentration (Grid test) and memory (Digits test) after drinking 250 ml of one of the following beverages: one with 80 mg caffeine, one with 1000 mg taurine, one with 80 mg caffeine plus 1000 mg taurine, a commercial energy drink (Red Bull®) or a placebo drink. Subjects were caffeine-consumers that avoided caffeine during the day of evaluation. All beverages were matched in flavor and other organoleptic properties to the commercial one, were bottled in dark plastic bottles and were administered in identical conditions to the participants. Differences between treatments were assessed using repeated measures and analysis of variance.

Results

The mean ± SD values of VO₂max, maximum heart rate, time to exhaustion, right handgrip strength, left handgrip strength, vertical jump, Grid test and Digits test were 61.3 ± 6.2 ml/kg.min, 196 ± 6.8 beats per min, 17 ± 1.2 min, 56.8 ± 6.6 kgf, 53.1 ± 5.9 kgf, 41.1 ± 3.8 cm, 19.9 ± 5.9 observed digits and 10.9 ± 3.1 remembered digits after drinking a placebo drink. Comparisons among the commercial drink, caffeine, taurine, caffeine plus taurine and placebo treatments did not show statistically differences in the results of the performed tests. No adverse effects were reported by the participants.

Conclusion

The consumption of caffeine (80 mg) and taurine (1000 mg) or their combination does not increase the physical and cognitive ability in young adults during exercise.

A prospective placebo controlled randomized study of caffeine in patients with supraventricular tachycardia undergoing electrophysiologic testing

INTRODUCTION

Patients with cardiac arrhythmias are generally instructed to avoid caffeine intake. A comprehensive evaluation of the electrophysiological effects of caffeine on atrial and ventricular tissues in humans has not previously been performed.

METHODS AND RESULTS

Eighty patients (31 men, mean age 49 ± 14 years) with symptomatic supraventricular tachycardia (SVT) undergoing an electrophysiologic study (EPS) prior to catheter ablation were randomized to receive oral caffeine or placebo. Caffeine at a dosage of 5 mg/kg (moderate intake) or placebo tablets were administered orally at a mean time of 57 ± 13 minutes prior to the EPS. The median (IQR) caffeine level in patients receiving caffeine was 7.4 μg/mL (4.7-8.7), as compared with 0.15 (0.00-0.61) in patients receiving placebo, P < 0.0001. Caffeine was associated with a significant increase in resting systolic and diastolic blood pressures as compared with placebo, while the resting heart rate was not significantly different between both groups. Caffeine was not associated with significant effects on the effective refractory period of the atrium or ventricle, as well as on AV node conduction. SVT was induced in all but 3 patients; there was no significant difference between groups receiving placebo or caffeine on SVT inducibility or the cycle length of induced tachycardias.

CONCLUSIONS

Caffeine, at moderate intake, was associated with significant increases in systolic and diastolic blood pressures, but had no evidence of a significant effect on cardiac conduction and refractoriness. Furthermore, no effect of caffeine on SVT induction or more rapid rates of induced tachycardias was found.

Pre-exercise nutrition: the role of macronutrients, modified starches and supplements on metabolism and endurance performance

Endurance athletes rarely compete in the fasted state, as this may compromise fuel stores. Thus, the timing and composition of the pre-exercise meal is a significant consideration for optimizing metabolism and subsequent endurance performance. Carbohydrate feedings prior to endurance exercise are common and have generally been shown to enhance performance, despite increasing insulin levels and reducing fat oxidation. These metabolic effects may be attenuated by consuming low glycemic index carbohydrates and/or modified starches before exercise. High fat meals seem to have beneficial metabolic effects (e.g., increasing fat oxidation and possibly sparing muscle glycogen). However, these effects do not necessarily translate into enhanced performance. Relatively little research has examined the effects of a pre-exercise high protein meal on subsequent performance, but there is some evidence to suggest enhanced pre-exercise glycogen synthesis and benefits to metabolism during exercise. Finally, various supplements (i.e., caffeine and beetroot juice) also warrant possible inclusion into pre-race nutrition for endurance athletes. Ultimately, further research is needed to optimize pre-exercise nutritional strategies for endurance performance.

Metabolic effects of a caffeinated sports drink consumed during a soccer match

The purpose of this study was to verify the effect of the intake of a caffeinated sport drink (CAFD) compared to a commercial carbohydrate drink (CHOD) on biochemical parameters and rate of perception exertion in youth soccer players. The experiment was setup in a double-blind crossover design where athletes consumed 5mL.Kg-1 body weight (BW) before the game and 3mL.Kg-1 BW every 15 minutes during the game. Intake of the CAFD resulted in increased blood glucose (BG) and blood lactate (BL) levels and average of maximum heart rate compared to consumption of the CHOD (p = 0.01). No difference was observed in the other variables. CAFD promoted greater plasmatic concentration of BG and BL compared with the CHOD. The CAFD did not increase the mobilization of free fatty acids, did not alter the plasma potassium concentration and was not able to reduce subjective perceived exertion.

Caffeine reduces myocardial blood flow during exercise

Caffeine consumption has been receiving increased interest from both the medical and lay press, especially given the increased amounts now available in energy products. Acute ingestion of caffeine usually increases cardiac work; however, caffeine impairs the expected proportional increase in myocardial blood flow to match this increased work of the heart, most notably during exercise. This appears to be mainly due to caffeine's effect on blocking adenosine-induced vasodilatation in the coronary arteries in normal healthy subjects. This review summarizes the available medical literature specifically relating to pure caffeine tablet ingestion and reduced exercise coronary blood flow, and suggests possible mechanisms. Further studies are needed to evaluate this effect for other common caffeine-delivery systems, including coffee, energy beverages, and energy gels, which are often used for exercise performance enhancement, especially in teenagers and young athletes.

Effects of supplemental GAKIC ingestion on resistance training performance in trained men

PURPOSE

Glycine-arginine-alpha-ketoisocaproic acid (GAKIC) is a relatively new supplement that athletes and fitness enthusiasts ingest to enhance performance during anaerobic exercise. Therefore, the purpose of this study was to investigate the potential ergogenic effects of GAKIC ingestion during multiple bouts of resistance exercise.

METHOD

Seven resistance-trained men participated in a randomized, counterbalanced, double-blind study. Participants were randomly assigned to placebo or GAKIC (10.2 g) and performed 5 sets of 75% of 1-repetition maximum leg press to failure. Total load volume was calculated by multiplying the 75% of 1-repetition maximum mass lifted by the sum of repetitions to failure. One week later, participants ingested the other supplement (placebo or GAKIC) and the same exercise protocol was performed (i.e., crossover). Blood lactate, glucose, and heart rate were determined preexercise and immediately postexercise.

RESULTS

GAKIC supplementation significantly increased leg-press total load volume (GAKIC = 31,564 +/- 9,132 kg; placebo = 25,763 +/- 6,595 kg, p < .05). Heart rate and blood lactate were significantly increased (p < .05) postexercise compared with preexercise but were not significantly different between GAKIC and placebo. No significant changes (p > .05) were detected for one-repetition maximum and blood glucose.

CONCLUSIONS

These novel findings suggest that GAKIC increases total work performed during repeated bouts of lower-body resistance exercise. Thus, our data suggest that GAKIC ingestion before weight training may increase the training volume of athletes and resistance-trained individuals.

Caffeine gum and cycling performance: a timing study

The purpose of this study was to determine the most efficacious time to administer caffeine (CAF) in chewing gum to enhance cycling performance. Eight male cyclists participated in 5 separate laboratory sessions. During the first visit, the subjects underwent a graded exercise test to determine maximal oxygen consumption (V[Combining Dot Above]O(2)max). During the next 4 visits, 3 pieces of chewing gum were administered at 3 time points (120-minute precycling, 60-minute precycling, and 5-minute precycling). In 3 of the 4 visits, at 1 of the time points mentioned previously, 300 mg of CAF was administered. During the fourth visit, placebo gum was administered at all 3 time points. The experimental trials were defined as follows: trial A (-120), trial B (-60), trial C (-5), and trial D (Placebo). After baseline measurements, time allotted for gum administration, and a standard warm-up, the participants cycled at 75% V[Combining Dot Above]O(2)max for 15 minutes then completed a 7-kJ·kg(-1) cycling time trial. Data were analyzed using a repeated measures analysis of variance. Cycling performance was improved in trial C (-5), but not in trial A (-120) or trial B (-60), relative to trial D (Placebo). CAF administered in chewing gum enhanced cycling performance when administered immediately prior, but not when administered 1 or 2 hours before cycling.

Herbs in exercise and sports

The use of herbs as ergogenic aids in exercise and sport is not novel. Ginseng, caffeine, ma huang (also called 'Chinese ephedra'), ephedrine and a combination of both caffeine and ephedrine are the most popular herbs used in exercise and sports. It is believed that these herbs have an ergogenic effect and thus help to improve physical performance. Numerous studies have been conducted to investigate the effects of these herbs on exercise performance. Recently, researchers have also investigated the effects of Eurycoma longifolia Jack on endurance cycling and running performance. These investigators have reported no significant improvement in either cycling or running endurance after supplementation with this herb. As the number of studies in this area is still small, more studies should be conducted to evaluate and substantiate the effects of this herb on sports and exercise performance. For instance, future research on any herbs should take the following factors into consideration: dosage, supplementation period and a larger sample size.

Energy drinks: a review of use and safety for athletes

Energy drinks have increased in popularity in adolescents and young adults; however, concerns have been raised regarding the ingredients in energy drinks and their potential negative effects on health. Caffeine, the most physiologically active ingredient in energy drinks, is generally considered safe by the US Food and Drug Administration (FDA), although adverse effects can occur at varying amounts. Guarana, which contains caffeine in addition to small amounts of theobromine, theophylline, and tannins, is also recognized as safe by the FDA, although it may lead to caffeine toxicity when combined with caffeine. The amount of ginseng in energy drinks is typically far below the amount used as a dietary supplement, and is generally considered safe. Taurine, an intracellular amino acid, has been reported to have positive inotropic effects; however, this claim is not supported by research. Most energy drinks also contain sugar in an amount that exceeds the maximum recommended daily amount. Young athletes are increasingly using energy drinks because of the ergogenic effects of caffeine and the other ingredients found in these beverages. Energy drinks combined with alcohol are also gaining popularity in young adults, which poses significant concerns about health risks. Other health concerns related to consumption of energy drinks include case reports of seizures and cardiac arrest following energy drink consumption and dental enamel erosion resulting from the acidity of energy drinks.

Influence of acetaminophen on performance during time trial cycling

To establish whether acetaminophen improves performance of self-paced exercise through the reduction of perceived pain, 13 trained male cyclists performed a self-paced 10-mile (16.1 km) cycle time trial (TT) following the ingestion of either acetaminophen (ACT) or a placebo (PLA), administered in randomized double-blind design. TT were completed in a significantly faster time ( t12 = 2.55, P < 0.05) under the ACT condition (26 min 15 s ± 1 min 36 s vs. 26 min 45 s ± 2 min 2 s). Power output (PO) was higher during the middle section of the TT in the ACT condition, resulting in a higher mean PO ( P < 0.05) (265 ± 12 vs. 255 ± 15 W). Blood lactate concentration (B[La]) and heart rate (HR) were higher in the ACT condition (B[La] = 6.1 ± 2.9 mmol/l; HR = 87 ± 7%max) than in the PLA condition (B[La] = 5.1 ± 2.6 mmol/l; HR = 84 ± 9%max) ( P < 0.05). No significant difference in rating of perceived exertion (ACT = 15.5 ± 0.2; PLA = 15.7 ± 0.2) or perceived pain (ACT = 5.6 ± 0.2; PLA = 5.5 ± 0.2) ( P > 0.05) was observed. Using acetaminophen, participants cycled at a higher mean PO, with an increased HR and B[La], but without changes in perceived pain or exertion. Consequently, completion time was significantly faster. These findings support the notion that exercise is regulated by pain perception, and increased pain tolerance can improve exercise capacity.

Efeito ergogênico de uma bebida esportiva cafeinada sobre a performance em testes de habilidades específicas do futebol

O consumo de cafeína tem demonstrado promover efeitos ergogênicos sobre a performance de atletas de esportes coletivos. O objetivo do presente estudo foi comparar o efeito de uma bebida esportiva cafeinada (BEC) frente a uma bebida carboidratada comercial (BCC) sobre a performance durante a execução de testes físico-motores de habilidades específicas do futebol. Os atletas foram submetidos a dois testes, salto vertical (Sargent Jump) e teste de agilidade (Illinois Agility Test), que foram executados antes e após as partidas durante as quais foram consumidas BEC (7% de carboidratos (CHO), concentração de cafeína correspondente a 250mg.l-1) ou BCC (sem cafeína, 7% de CHO). Os resultados demonstraram que BEC aumentou significantemente (p < 0,01) a altura atingida no salto em relação ao momento anterior ao seu consumo e em comparação com a BCC (p = 0,02). BCC não promoveu aumento na potência de membros inferiores. Tanto BEC (p = 0,62) quanto BCC (p = 0,93), não aumentaram a agilidade no teste realizado após a partida em comparação com o realizado anteriormente. Ambas as bebidas não foram capazes de melhorar o desempenho na execução do teste de agilidade após a partida (p = 0,95). O consumo de BEC proporcionou um efeito ergogênico para jogadores de futebol, aumentando a potência de membros inferiores relacionada com a força explosiva. Contudo, quanto à agilidade não foi possível identificar vantagens no desempenho.

Effect of caffeine as an ergogenic aid during anaerobic exercise performance in caffeine naïve collegiate football players

Research suggests that caffeine may improve performance in aerobic exercise; the evidence for anaerobic performance is mixed. This study examined the effect of caffeine (5 mg/kg body weight [BW]) vs. placebo on performance-based anaerobic exercise tests used during the National Football League (NFL) Combine. Collegiate football athletes (n = 17; 20 +/- 2 yr; body mass index 29.4 +/- 3.6 kg/m) completed 2 study visits, 1 week apart. Participants were low caffeine users with a reported average intake of 16 +/- 20 mg/day. On the day of testing, participants ingested a caffeinated (5 mg/kg BW caffeine + 0.125 g/kg BW carbohydrate) or placebo (0.125 g/kg BW carbohydrate) beverage, ate a light meal, and completed 3 exercise tests (40-yard dash, 20-yard shuttle, and a bench press) 60 minutes later. Borg's rating of perceived exertion (RPE) was recorded after each exercise test. Heart rate (HR) and blood pressure (BP) were monitored (pre-exercise and postexercise). Data were analyzed using paired t-tests, Wilcoxon signed rank test, and repeated measures analysis of variance. No significant differences were found between treatments for the exercise tests (40-yard dash: 5.01 +/- 0.25 vs. 5.03 +/- 0.26 s, p = 0.43; 20-yard shuttle: 4.64 +/- 0.19 vs. 4.66 +/- 0.24 s, p = 0.51; bench press: 17 +/- 8 vs. 17 +/- 8 reps, p = 0.51; caffeine vs. placebo, respectively). However, 59% of the participants improved in performance with the caffeine during the bench press and the 40-yard dash. No differences were found between treatments for RPE, HR, and BP. Caffeine did not improve performance for anaerobic exercise tests used at the NFL Combine in caffeine naïve male football athletes.

Acute effects of a thermogenic nutritional supplement on cycling time to exhaustion and muscular strength in college-aged men

Background

The purpose of the present study was to examine the acute effects of a thermogenic nutritional supplement containing caffeine, capsaicin, bioperine, and niacin on muscular strength and endurance performance.

Methods

Twenty recreationally-active men (mean ± SD age = 21.5 ± 1.4 years; stature = 178.2 ± 6.3 cm; mass = 76.5 ± 9.9 kg; VO_{2 PEAK} = 3.05 ± 0.59 L/min^-1) volunteered to participate in this randomized, double-blinded, placebo-controlled, cross-over study. All testing took place over a three-week period, with each of the 3 laboratory visits separated by 7 days (± 2 hours). During the initial visit, a graded exercise test was performed on a Lode Corival cycle ergometer (Lode, Groningen, Netherlands) until exhaustion (increase of 25 W every 2 min) to determine the maximum power output (W) at the VO_{2 PEAK} (Parvo Medics TrueOne^® 2400 Metabolic Measurement System, Sandy, Utah). In addition, one-repetition maximum (1-RM) strength was assessed using the bench press (BP) and leg press (LP) exercises. During visits 2 and 3, the subjects were asked to consume a capsule containing either the active supplement (200 mg caffeine, 33.34 mg capsaicin, 5 mg bioperine, and 20 mg niacin) or the placebo (175 mg of calcium carbonate, 160 mg of microcrystalline cellulose, 5 mg of stearic acid, and 5 mg of magnesium stearate in an identical capsule) 30 min prior to the testing. Testing included a time-to-exhaustion (TTE) ride on a cycle ergometer at 80% of the previously-determined power output at VO_{2 PEAK} followed by 1-RM LP and BP tests.

Results

There were no differences (p > 0.05) between the active and placebo trials for BP, LP, or TTE. However, for the BP and LP scores, the baseline values (visit 1) were less than the values recorded during visits 2 and 3 (p ≤ 0.05).

Conclusion

Our findings indicated that the active supplement containing caffeine, capsaicin, bioperine, and niacin did not alter muscular strength or cycling endurance when compared to a placebo trial. The lack of increases in BP and LP strength and cycle ergometry endurance elicited by this supplement may have been related to the relatively small dose of caffeine, the high intensity of exercise, the untrained status of the participants, and/or the potential for caffeine and capsaicin to increase carbohydrate oxidation.

Cognitive Performance during Sustained Wakefulness: A Low Dose of Caffeine Is Equally Effective as Modafinil in Alleviating the Nocturnal Decline

Cognitive performance at night exhibits a substantial drop, typically before dawn. One of the means of dealing with this phenomenon, as well as with the accompanying sleepiness during sustained wakefulness, is the administration of stimulants. The most widely used and well-documented stimulants are caffeine, amphetamines, and modafinil. Of these, amphetamines are the least recommended, as they may severely affect behavior. Caffeine and modafinil seem to produce relatively milder side effects and usually only at high doses. Previous comparison studies have revealed equal efficacy of both the stimulants in maintaining alertness and performance during sustained wakefulness. However, these studies used relatively high, and thus not completely safe, doses of these drugs (600 mg caffeine and 400 mg modafinil). Therefore, the aim of the present study was to assess the efficacy of a low and medically safe dose of caffeine (200 mg) and modafinil (200 mg) in maintaining cognitive performance during sustained wakefulness. A flight simulation task was chosen for the assessment of the stimulants in a counter-balanced, within-subject design under four different conditions: baseline (no drugs), placebo, caffeine (200 mg), and modafinil (200 mg). The equal effectiveness of both drugs in abolishing the nocturnal drop in cognitive performance, as well as of oral temperature and blood pressure, supported the use of low doses of caffeine and modafinil for the maintenance of alertness in healthy subjects during sustained wakefulness.

Caffeine and sports performance

Athletes are among the groups of people who are interested in the effects of caffeine on endurance and exercise capacity. Although many studies have investigated the effect of caffeine ingestion on exercise, not all are suited to draw conclusions regarding caffeine and sports performance. Characteristics of studies that can better explore the issues of athletes include the use of well-trained subjects, conditions that reflect actual practices in sport, and exercise protocols that simulate real-life events. There is a scarcity of field-based studies and investigations involving elite performers. Researchers are encouraged to use statistical analyses that consider the magnitude of changes, and to establish whether these are meaningful to the outcome of sport. The available literature that follows such guidelines suggests that performance benefits can be seen with moderate amounts (~3 mg.kg-1 body mass) of caffeine. Furthermore, these benefits are likely to occur across a range of sports, including endurance events, stop-and-go events (e.g., team and racquet sports), and sports involving sustained high-intensity activity lasting from 1-60 min (e.g., swimming, rowing, and middle and distance running races). The direct effects on single events involving strength and power, such as lifts, throws, and sprints, are unclear. Further studies are needed to better elucidate the range of protocols (timing and amount of doses) that produce benefits and the range of sports to which these may apply. Individual responses, the politics of sport, and the effects of caffeine on other goals, such as sleep, hydration, and refuelling, also need to be considered.

Consumption of dietary caffeine and coffee in physically active populations: physiological interactions

Caffeine is a proven ergogenic aid, increasing athletic performance, endurance, and mental chronometry at doses as low as 1–3 mg·kg–1. As coffee is a readily available and commonly ingested form of caffeine, the two are often equated. However, coffee also contains hundreds of other biologically active compounds, many of which are metabolically distinct from caffeine. The purpose of this review was to examine the prevalence of coffee and (or) caffeine consumption among elite Canadian athletes, and to delineate the effects of coffee and caffeine on physical activity, weight maintenance, performance, and metabolism. A total of 270 self-reported 3-day food records were examined for caffeine intake from athletes registered with Canadian Sport Centres in 2005 and 2006. Athletes ranged in age from 16–45 years, and competed in 38 different sports. Results showed that 30% of athletes ingested >1 mg·kg–1·day–1 from a variety of sources. Average daily intake was 0.85 ± 13 mg·kg–1. Caffeine intake was not correlated with any 1 sport; the 10 highest caffeine users were athletes from 9 different sports, including skill, endurance, and power sports. No differences were noted for average caffeine ingestion between summer and winter sports. High caffeine intakes corresponded to coffee ingestion, with the 25 highest individual intakes (193–895 mg·day–1) from coffee drinkers. In summary, it can be concluded that the majority of high-level Canadian athletes consume dietary caffeine primarily in the form of coffee. However, levels consumed are insufficient to elicit performance enhancement. Potential detrimental effects of caffeine consumption on exercise performance include gastric upset, withdrawal, sleep disturbance, and interactions with other dietary supplements.

The effect of ephedra and caffeine on maximal strength and power in resistance-trained athletes

Caffeine and ephedrine-related alkaloids recently have been removed from International Olympic Committee banned substances lists, whereas ephedrine itself is now permissible at urinary concentrations less than 10 mug.mL. The changes to the list may contribute to an increased use of caffeine and ephedra as ergogenic aids by athletes. Consequently, we sought to investigate the effects of ingesting caffeine (C) or a combination of ephedra and caffeine (C + E) on muscular strength and anaerobic power using a double-blind, crossover design. Forty-five minutes after ingesting a glucose placebo (P: 300 mg), C (300 mg) or C + E (300 mg + 60 mg), 9 resistance-trained male participants were tested for maximal strength by bench press [BP; 1 repetition maximum (1RM)] and latissimus dorsi pull down (LP; 1RM). Subjects also performed repeated repetitions at 80% of 1RM on both BP and LP until exhaustion. After this test, subjects underwent a 30-second Wingate test to determine peak anaerobic cycling power, mean power, and fatigue index. Although subjects reported increased alertness and enhanced mood after supplementation with caffeine and ephedra, there were no significant differences between any of the treatments in muscle strength, muscle endurance, or peak anaerobic power. Our results do not support the contention that supplementation with ephedra or caffeine will enhance either muscle strength or anaerobic exercise performance.

Low doses of caffeine reduce heart rate during submaximal cycle ergometry

Background

The purpose of this study was to examine the cardiovascular effects of two low-levels of caffeine ingestion in non habitual caffeine users at various submaximal and maximal exercise intensities.

Methods

Nine male subjects (19–25 yr; 83.3 ± 3.1 kg; 184 ± 2 cm), underwent three testing sessions administered in a randomized and double-blind fashion. During each session, subjects were provided 4 oz of water and a gelatin capsule containing a placebo, 1.5 mg/kg caffeine, or 3.0 mg/kg caffeine. After thirty minutes of rest, a warm-up (30 Watts for 2 min) the pedal rate of 60 rpm was maintained at a steady-state output of 60 watts for five minutes; increased to 120 watts for five minutes and to 180 watts for five minutes. After a 2 min rest the workload was 180 watts for one minute and increased by 30 watts every minute until exhaustion. Heart rate (HR) was measured during the last 15-seconds of each minute of submaximal exercise. Systolic blood pressure (BP) was measured at rest and during each of the three sub-maximal steady state power outputs. Minute ventilation (V_E), Tidal volume (V_T), Breathing frequency (Bf), Rating of perceived exertion (RPE), Respiratory exchange ratio (RER), and Oxygen consumption (VO₂) were measured at rest and during each minute of exercise.

Results

Caffeine at 1.5 and 3.0 mg/kg body weight significantly lowered (p < 0.05) HR during all three submaximal exercise intensities compared to placebo (range – 4 to 7 bpm lower) but not at rest or maximal exercise. BP was significantly higher (p < 0.05) at rest and after the 3 mg/kg caffeine vs placebo (116 ± 13 vs 123 ± 10 mm Hg). Neither dose of caffeine had any effect on BP during submaximal exercise. Caffeine had no effect on V_E, V_T, VO₂, RPE, maximal power output or time to exhaustion.

Conclusion

In non habitual caffeine users it appears that consuming a caffeine pill (1.5 & 3.0 mg/kg) at a dose comparable to 1–3 cups of coffee lowers heart rate during submaximal exercise but not at near maximal and maximal exercise. In addition, this caffeine dose also only appears to affect systolic blood pressure at rest but not during cycling exercise.

Acute effects of ingesting Java Fittrade mark energy extreme functional coffee on resting energy expenditure and hemodynamic responses in male and female coffee drinkers

BACKGROUND

The purpose of this study was to examine the effects of a functional coffee beverage containing additional caffeine, green tea extracts, niacin and garcinia cambogia to regular coffee to determine the effects on resting energy expenditure (REE) and hemodynamic variables.

METHODS

Subjects included five male (26 +/- 2.1 y, 97.16 +/- 10.05 kg, 183.89 +/- 6.60 cm) and five female (28.8 +/- 5.3 y, 142.2 +/- 12.6 lbs) regular coffee drinkers. Subjects fasted for 10 hours and were assessed for 1 hour prior (PRE) and 3 hours following 1.5 cups of coffee ingestion [JavaFittrade mark Energy Extreme (JF) ~400 mg total caffeine; Folgers (F) ~200 mg total caffeine] in a double-blind, crossover design. REE, resting heart rate (RHR), and systolic (SBP) and diastolic (DBP) blood pressure was assessed at PRE and 1, 2, and 3-hours post coffee ingestion. Data were analyzed by three-factor repeated measures ANOVA (p < 0.05).

RESULTS

JF trial resulted in a significant main effect for REE (p < 0.01), SBP (p < 0.01), RER (p < 0.01), and VO2 (p < 0.01) compared to F, with no difference between trials on the RHR and DBP variables. A significant interaction for trial and time point (p < 0.05) was observed for the variable REE. The JF trial resulted in a significant overall mean increase in REE of 14.4% (males = 12.1%, females = 17.9%) over the observation period (p < 0.05), while the F trial produced an overall decrease in REE of 5.7%. SBP was significantly higher in the JF trial; however, there was no significant increase from PRE to 3-hours post.

CONCLUSION

Results from this study suggest that JavaFittrade mark Energy Extreme coffee is more effective than Folgers regular caffeinated coffee at increasing REE in regular coffee drinkers for up to 3 hours following ingestion without any adverse hemodynamic effects.

Caffeine As an Ergogenic Aid

Caffeine is a naturally occurring substance that is widely consumed in a variety of forms. It produces multiple physiologic effects throughout the body. It is thought that this is mediated mainly through action at centrally located adenosine receptors. Caffeine has been studied for its potential use as an ergogenic aid. Several studies have demonstrated an improvement in exercise performance in submaximal endurance activities. Its potential ergogenic effect in acute, high-intensity exercise is less clear. Because of its potential use as an ergogenic aid, it use in sports is regulated by most sanctioning bodies.

Effects of caffeine ingestion on rating of perceived exertion during and after exercise: a meta-analysis

The purpose of this study was to use the meta-analytic approach to examine the effects of caffeine ingestion on ratings of perceived exertion (RPE). Twenty-one studies with 109 effect sizes (ESs) met the inclusion criteria. Coding incorporated RPE scores obtained both during constant load exercise (n=89) and upon termination of exhausting exercise (n=20). In addition, when reported, the exercise performance ES was also computed (n=16). In comparison to placebo, caffeine reduced RPE during exercise by 5.6% (95% CI (confidence interval), -4.5% to -6.7%), with an equivalent RPE ES of -0.47 (95% CI, -0.35 to -0.59). These values were significantly greater (P<0.05) than RPE obtained at the end of exercise (RPE % change, 0.01%; 95% CI, -1.9 to 2.0%; RPE ES, 0.00, 95% CI, -0.17 to 0.17). In addition, caffeine improved exercise performance by 11.2% (95% CI; 4.6-17.8%). Regression analysis revealed that RPE obtained during exercise could account for approximately 29% of the variance in the improvement in exercise performance. The results demonstrate that caffeine reduces RPE during exercise and this may partly explain the subsequent ergogenic effects of caffeine on performance.

Effects of acute modafinil ingestion on exercise time to exhaustion

PURPOSE

The purpose of this study was to investigate the effect of acute ingestion of modafinil (M) on time to exhaustion during high-intensity exercise. Modafinil (M) is a psychostimulant developed to treat narcolepsy, with "arousal" properties attributed to an increased release of dopamine in the CNS. Because other stimulants with similar properties have ergogenic effects, it was hypothesized that acute treatment with M would enhance physical performance.

METHODS

Fifteen healthy male subjects, with a maximal aerobic power (VO2max) of 47 +/- SD 8 mL x kg x min, exercised on a cycle ergometer for 5 min at 50% VO2max and then at approximately 85% VO2max to exhaustion. They did this weekly for 3 wk: a control trial (C) the first week, and then 3 h after ingesting either placebo (P) or M (4 mg x kg) during the remaining 2 wk. The P and M trials were conducted with a balanced order, double-blind design.

RESULTS

: Mean +/- SD times to exhaustion at 85% VO2max (TE) were 14.3 +/- 2.8, 15.6 +/- 3.8 and 18.3 +/- 3.5 min for the C, P, and M trials, respectively. TE for M was significantly longer than for the C and P trials. Oxygen uptake at exhaustion was slightly but significantly greater for M compared with P and C. HR increased with time and was further elevated by M. Subjective ratings of perceived exertion (RPE) were significantly lower for M compared with C and P but only after 10 min of exercise at 85% VO2max.

CONCLUSION

Acute ingestion of modafinil prolonged exercise time to exhaustion at 85% VO2max and reduced RPE. The RPE results suggest that the dampening of the sensation of fatigue was likely a factor responsible for the enhanced performance.

Caffeine and Ephedrine

Preparations containing caffeine and ephedrine have become increasingly popular among sportspersons in recent years as a means to enhance athletic performance. This is due to a slowly accumulating body of evidence suggesting that combination of the two drugs may be more efficacious than each one alone. Caffeine is a compound with documented ergogenicity in various exercise modalities, while ephedrine and related alkaloids have not been shown, as yet, to result in any significant performance improvements. Caffeine-ephedrine mixtures, however, have been reported in several instances to confer a greater ergogenic benefit than either drug by itself. Although data are limited and heterogeneous in nature to allow for reaching consensus, the increase in performance is a rather uniform finding as it has been observed during submaximal steady-state aerobic exercise, short- and long-distance running, maximal and supramaximal anaerobic cycling, as well as weight lifting. From the metabolic point of view, combined ingestion of caffeine and ephedrine has been observed to increase blood glucose and lactate concentrations during exercise, wheareas qualitatively similar effects on lipid fuels (free fatty acids and glycerol) are less pronounced. In parallel, epinephrine and dopamine concentrations are significantly increased, wheareas the effects on norepinephrine are less clear. With respect to pulmonary gas exchange during short-term intense exercise, no physiologically significant effects have been reported following ingestion of caffeine, ephedrine or their combination. Yet, during longer and/or more demanding efforts, some sporadic enhancements have indeed been shown. On the other hand, a relatively consistent cardiovascular manifestation of the latter preparation is an increase in heart rate, in addition to that caused by exercise alone. Finally, evidence to date strongly suggests that caffeine and ephedrine combined are quite effective in decreasing the rating of perceived exertion and this seems to be independent of the type of activity being performed. In general, our knowledge and understanding of the physiological, metabolic and performance-enhancing effects of caffeine-ephedrine mixtures are still in their infancy. Research in this field is probably hampered by sound ethical concerns that preclude administration of potentially hazardous substances to human volunteers. In contrast, while it is certainly true that caffeine and especially ephedrine have been associated with several acute adverse effects on health, athletes do not seem to be concerned with these, as long as they perceive that their performance will improve. In light of the fact that caffeine and ephedra alkaloids, but not ephedrine itself, have been removed from the list of banned substances, their use in sports can be expected to rise considerably in the foreseeable future. Caffeine-ephedra mixtures may thus become one of most popular ergogenic aids in the years to come and while they may indeed prove to be one of the most effective ones, and probably one of the few legal ones, whether they also turn out to be one of the most dangerous ones awaits to be witnessed.