The effects of caffeine ingestion on performance time, speed and power during a laboratory-based 1 km cycling time-trial

Caffeine and sport

Caffeine is a trimethylxanthine found in coffee and several other foods and beverages. Its stimulatory effects make it an interesting strategy to boost performance for athletic populations. Scientific evidence supports its efficacy to improve high-intensity endurance exercise, explosive and high-intensity efforts, resistance exercise, team sports and combat sports, though individual variation in the ergogenic response to caffeine exists. Supplementation can be taken in many forms including dissolved in water, via capsules, coffee, energy drinks and caffeinated gum; ingestion via capsules, dissolved in water or in caffeinated gum appear to be most effective. Variability in the exercise response following caffeine supplementation may be explained by genetic factors or habitual caffeine consumption. Caffeine is an excellent supplement for athletes looking to improve their exercise performance, though some consideration of side-effects and impact on sleep are warranted.

Does Single or Combined Caffeine and Taurine Supplementation Improve Athletic and Cognitive Performance without Affecting Fatigue Level in Elite Boxers? A Double-Blind, Placebo-Controlled Study

In previous studies, the effect of single or combined intake of caffeine (CAF) and taurine (TAU) on exercise performance was investigated. However, the potential synergistic effect on physical and cognitive performance after fatigue induced by anaerobic exercise is unknown. The effects of single and combination CAF and TAU supplementation on the Wingate test in elite male boxers and to evaluate balance, agility and cognitive performance after fatigue are being investigated for the first time in this study. Twenty elite male boxers 22.14 ± 1.42 years old were divided into four groups in this double-blind, randomized crossover study: CAF (6 mg/kg of caffeine), TAU (3 g single dose of taurine), CAF*TAU (co-ingestion of 3 g single dose of taurine and 6 mg/kg of caffeine) and PLA (300 mg maltodextrin). The findings are as follows: co-ingestion of CAF*TAU, improved peak (W/kg), average (W), minimum (W) power, time to reach (s), and RPE performances compared to the PLA group significantly (p < 0.05). Similarly, it was determined that a single dose of TAU, created a significant difference (p < 0.05) in peak power (W/kg), and average and minimum power (W) values compared to the CAF group. According to the balance and agility tests performed after the Wingate test, co-ingestion of CAF*TAU revealed a significant difference (p < 0.05) compared to the PLA group. In terms of cognitive performance, co-ingestion of CAF*TAU significantly improved the neutral reaction time (ms) compared to the TAU, CAF and PLA groups. As a result, elite male boxers performed better in terms of agility, balance and cognitive function when they consumed a combination of 6 mg/kg CAF and 3 g TAU. It has been determined that the combined use of these supplements is more effective than their single use.

Acute Effects of Caffeine on Overall Performance in Basketball Players—A Systematic Review

Caffeine supplementation has become increasingly popular among athletes. The benefits of caffeine include delaying the negative effects of fatigue, maintaining a high level of physical and mental performance, and improving certain abilities necessary for sport success. Given the complex nature of basketball, caffeine could be a legal, ergogenic stimulant substance, which will positively affect overall basketball performance. The purpose of this systematic review was to summarize evidence for the effect of acute caffeine ingestion on variables related to the basketball performance. Web of Science, PubMed, Scopus and ProQuest, MEDLINE, and ERIC databases were searched up to February 2021. Studies that measured the acute effect of caffeine on basketball performance were included and analyzed. Eight studies published between 2000 and 2021 were included in the analysis. Pre-exercise caffeine intake increased vertical jump height, running time at 10 and 20 m without the ball, overall basketball performance (number of body impacts, number of free throws, rebounds, and assists) during simulated games, and reduced the time required to perform a basketball-specific agility test. Equivocal results between caffeine and placebo groups were found for aerobic capacity, free throw and three-point accuracy, and dribbling speed. Pre-exercise caffeine ingestion did not affect RPE, but insomnia and urinary excretion were increased. The pre-exercise ingestion of 3 and 6 mg/kg caffeine was found to be effective in increasing several physical performance variables in basketball players during sport-specific testing and simulated matches. However, considering the intermittent nature and complexity of basketball, and individual differences between players, future studies are needed.

Caffeine Supplementation Strategies Among Endurance Athletes

Caffeine is widely accepted as an endurance-performance enhancing supplement. Most scientific research studies use doses of 3–6 mg/kg of caffeine 60 min prior to exercise based on pharmacokinetics. It is not well understood whether endurance athletes employ similar supplementation strategies in practice. The purpose of this study was to investigate caffeine supplementation protocols among endurance athletes. A survey conducted on Qualtrics returned responses regarding caffeine supplementation from 254 endurance athletes (f = 134, m =120; age = 39.4 ± 13.9 y; pro = 11, current collegiate athlete = 37, recreational = 206; running = 98, triathlon = 83, cycling = 54, other = 19; training days per week = 5.4 ± 1.3). Most participants reported habitual caffeine consumption (85.0%; 41.2% multiple times daily). However, only 24.0% used caffeine supplements. A greater proportion of men (31.7%) used caffeine supplements compared with women (17.2%; p = 0.007). Caffeine use was also more prevalent among professional (45.5%) and recreational athletes (25.1%) than in collegiate athletes (9.4%). Type of sport (p = 0.641), household income (p = 0.263), education (p = 0.570) or working with a coach (p = 0.612) did not have an impact on caffeine supplementation prevalence. Of those reporting specific timing of caffeine supplementation, 49.1% and 34.9% reported consuming caffeine within 30 min of training and races respectively; 38.6 and 36.5% used caffeine 30–60 min before training and races. Recreational athletes reported consuming smaller amounts of caffeine before training (1.6 ± 1.0 mg/kg) and races (2.0 ± 1.2 mg/kg) compared with collegiate (TRG: 2.1 ± 1.2 mg/kg; RACE: 3.6 ± 0.2 mg/kg) and professional (TRG: 2.4 ± 1.1 mg/kg; RACE: 3.5 ± 0.6 mg/kg) athletes. Overall, participants reported minor to moderate perceived effectiveness of caffeine supplementation (2.31 ± 0.9 on a four-point Likert-type scale) with greatest effectiveness during longer sessions (2.8 ± 1.1). It appears that recreational athletes use lower caffeine amounts than what has been established as ergogenic in laboratory protocols; further, they consume caffeine closer to exercise compared with typical research protocols. Thus, better education of recreational athletes and additional research into alternative supplementation strategies are warranted.

N1-Methylnicotinamide: Is It Time to Consider as a Dietary Supplement for Athletes?

Abstract:

Exercise is considered to be a “medicine” due to its modulatory roles in metabolic disorders such as diabetes and obesity. The intensity and duration of exercise determine the mechanism of energy production by various tissues of the body, especially by muscles, in which the requirement for adenosine triphosphate (ATP) increases by as much as 100-fold. Naturally, athletes try to improve their exercise performance by dietary supplementation with, e.g., vitamins, metabolites, and amino acids. MNAM, as a vitamin B3 metabolite, reduces serum levels and liver contents of triglycerides, and cholesterol and induces lipolysis. It stimulates gluconeogenesis and prohibits liver cholesterol and fatty acid synthesis through the expression of sirtuin1 (SIRT1). It seems that MNAM is not responsible for the actions of NNMT in the adipose tissues as MNAM inhibits the activity of NNMT in the adipose tissue and acts like inhibitors of its activity. NNMT-MNAM axis is more activated in the muscles of participants who were undergoing the high-volume-low-intensity exercise and caloric restriction. Therefore, MNAM could be an important myokine during exercise and fasting where it provides the required energy for muscles through the induction of lipolysis and gluconeogenesis in the liver and adipose tissues, respectively. Increased levels of MNAM in exercise and fasting led us to propose that the consumption of MNAM during training especially endurance training could boost exercise capacity and improves performance. Therefore, in this review, we shed light on the potential of MNAM as a dietary supplement in sports medicine.

CYP1A2 Genotype Polymorphism Influences the Effect of Caffeine on Anaerobic Performance in Trained Males

The purpose was to investigate the effects of CYP1A2 -163C > A polymorphism on the effects of acute caffeine (CAF) supplementation on anaerobic power in trained males. Sixteen trained males (age: 21.6 ± 7.1 years; height: 179.7 ± 5.6 cm; body mass: 72.15 ± 6.8 kg) participated in a randomized, double-blind, placebo (PLA) controlled crossover design. Participants supplemented with CAF (6 mg/kg of body mass) and an isovolumetric PLA (maltodextrin) in random order and separated by 7 days, before an all-out 30-s anaerobic cycling test to determine peak, average, and minimum power output, and fatigue index. Genomic deoxyribonucleic acid was extracted to identify each participants CYP1A2 genotype. Six participants expressed AA homozygote and 10 expressed C alleles. There was a treatment by genotype interaction for peak power output (p = .041, η2 = .265, observed power = 0.552) with only those expressing AA genotype showing improvement following CAF supplementation compared with PLA (CAF: 693 ± 108 watts vs. PLA: 655 ± 97 watts; p = .039), while no difference between treatments was noted in those expressing C alleles (CAF: 614 ± 92 watts vs. PLA: 659 ± 144 watts; p = .135). There were no other interaction or main effects for average or minimum power output, or fatigue index (p > .05). In conclusion, the ingestion of 6 mg/kg of CAF improved peak power output only in participants with the AA genotype compared with PLA; however, expression of the CYP1A2 did not influence average or minimum power output or fatigue index.

Nonplacebo Controls to Determine the Magnitude of Ergogenic Interventions: A Systematic Review and Meta-analysis

INTRODUCTION

Placebos are used as a control treatment that is meant to be indistinguishable from the active intervention. However, where substantive placebo effects may occur, studies that do not include a nonplacebo control arm may underestimate the overall effect of the intervention (active plus placebo components). This study aimed to determine the relative magnitude of the placebo effect associated with nutritional supplements (caffeine and extracellular buffers) by meta-analyzing data from studies containing both placebo and nonplacebo control sessions.

METHODS

Bayesian multilevel meta-analysis models were used to estimate pooled effects and express the placebo effect as a percentage of the overall intervention effect.

RESULTS

Thirty-four studies were included, with the median pooled effect size (ES0.5) indicating a very small (ES0.5 = 0.09 (95% credible interval (CrI), 0.01-0.17)) improvement in the performance of placebo compared with control. There was no moderating effect of exercise type (capacity or performance), exercise duration, or training status. The comparison between active intervention and control indicated a small to medium effect (ES0.5 = 0.37 (95% CrI, 0.20-0.56)). Expressed in relative terms, the placebo effect was equivalent to 25% (75% CrI, 16%-35%) and 59% (75% CrI, 34%-94%) of the total intervention effect for buffers and caffeine.

CONCLUSIONS

These results demonstrate a very small but potentially important placebo effect with nutritional supplementation studies. A substantive proportion of supplement effects may be due to placebo effects, with the relative proportion influenced by the magnitude of the overall ergogenic effect. Where feasible, intervention studies should use nonplacebo control-arm comparators to identify the proportion of the effect estimated to come from placebo effects and avoid underestimating the overall benefits that the physiological plus psychobiological aspects associated with an intervention provide in the real world.

Flattened cola improves high-intensity interval performance in competitive cyclists

PURPOSE

Some cyclists consume flattened cola during competitive events, but limited research has investigated if cola beverages elicit ergogenic effects, particularly on high-intensity exercise performance. Whether the potentially beneficial effects of cola are due to the caffeine and/or the carbohydrate content is also unclear. This study assessed the ergogenic effects of different cola beverages on performance during a constant power bout (CPB) and subsequent high-intensity interval efforts in competitive cyclists.

METHODS

In a randomized, double-blind, cross-over design, competitive cyclists (n = 13; [Formula: see text]O_2max 65.7 ± 5.9 ml kg^-1 min^-1) completed a 45-min CPB at 69% of maximum workload (W_max), followed by four maximal 1-min high-intensity intervals (HII) against a resistance of 0.5 N kg^-1. Participants consumed 16 ml kg^-1 total (intermittantly at four time points) of flattened decaffinated diet cola (PLA), caffeinated diet cola (CAF) or cola containing caffeine and carbohydrates (CAF + CHO).

RESULTS

During the CPB, ratings of perceived exertion were lower in the CAF + CHO and CAF conditions compared to PLA (both, P < 0.04). Compared to PLA, CAF + CHO and CAF similarly increased (all, P < 0.049) mean power (CAF + CHO: 448 ± 51 W; CAF: 448 ± 50 W; PLA: 434 ± 57 W), minimum power (CAF + CHO: 353 ± 45 W; CAF: 352 ± 51 W; PLA: 324 ± 49 W) and total work (CAF + CHO: 26.9 ± 3.1 kJ; CAF: 26.9 ± 3.0 kJ; PLA: 26.0 ± 3.4 kJ), but not peak power (CAF + CHO: 692 ± 117 W; CAF: 674 ± 114 W; PLA: 670 ± 113 W; all, P > 0.57) during the HII.

CONCLUSION

Cola containing caffeine with or without carbohydrates favorably influenced perceived effort during the CPB and enhanced mean and minimum power during repeated maximal intervals. We provide evidence supporting the consumption of commercially available cola for high-intensity cycling in competitive cyclists.

Caffeine metabolites are associated with different forms of caffeine supplementation and with perceived exertion during endurance exercise

This investigation compared the urine caffeine metabolites produced from different forms of caffeine supplementation given to runners 15 minutes before a series of 5-km running trials. Fourteen amateur competitive runners completed a series of self-paced outdoor time trials following ingestion of placebo or one of three alternate forms of caffeine supplement. Trials were randomized in a crossover design with equivalent doses of caffeine (4.0 mg.kg-1) administered 15 minutes before each trial via chewing gum, a novel dissolvable mouth strip or tablet. Runners produced a urine sample following each caffeinated trial that was tested for caffeine and its metabolites by high-performance liquid chromatography. The tablet form of caffeine produced a lower (p = 0.04) urinary ratio of the metabolite paraxanthine to caffeine compared with either gum or strip. Independently of caffeine delivery mode, subjects who metabolized a higher proportion of caffeine to paraxanthine recorded a lower (p = 0.01) perceived exertion. We demonstrate that oral swallowed caffeine administered 15 minutes before 5-km running is less metabolized compared with caffeinated products designed to be chewed or dissolved in the mouth. We suggest the metabolism of caffeine to paraxanthine has an inverse relationship with perceived exertion independently of caffeine delivery mode.

Caffeine and Exercise Performance: Possible Directions for Definitive Findings

Caffeine is one of the most studied supplements in the world. Studies correlate its use to increased exercise performance in endurance activities, as well as its possible ergogenic effects for both intermittent and strength activities. Recent findings show that caffeine may increase or decrease exercise performance. These antagonist responses may occur even when using the same dosage and for individuals with the same characteristics, making it challenging to explain caffeine's impact and applicability. This review article provides an analytic look at studies involving the use of caffeine for human physical performance, and addresses factors that could influence the ergogenic effects of caffeine on different proposed activities. These factors subdivide into caffeine effects, daily habits, physiological factors, and genetic factors. Each variable has been focused on by discussions to research related to caffeine. A better understanding and control of these variables should be considered in future research into personalized nutritional strategies.

Effect of Caffeine on Endurance Performance in Athletes May Depend on HTR2A and CYP1A2 Genotypes

Guest, NS, Corey, P, Tyrrell, PN, and El-Sohemy, A. Effect of caffeine on endurance performance in athletes may depend on HTR2A and CYP1A2 genotypes. J Strength Cond Res XX(X): 000-000, 2020-This investigation determined whether variation in the HTR2A (serotonin receptor) gene modifies the ergogenic effects of caffeine on endurance and further modifies performance by the CYP1A2 genotype. Male athletes (n = 100; 25 ± 4 years) completed 10-km cycling time trials under 3 conditions as follows: 0, 2, or 4 mg of caffeine per kg body mass. Using a randomized, double-blinded, placebo-controlled design, data were analyzed using analysis of covariance to compare changes in cycling time between placebo (0 mg·kg) and each caffeine dose and adjusted for the placebo trial and order of treatment. A significance of ρ ≤ 0.05 was used. Subjects were genotyped for HTR2A (rs6313) and CYP1A2 (rs762551). A significant caffeine-HTR2A interaction (p = 0.003) was observed; however, after adjustment for placebo trials, the interaction was no longer significant (p = 0.37). Because of the strong caffeine-CYP1A2 interaction (p < 0.0001) previously reported in these subjects, where the 4-mg dose resulted in divergent effects (slower and faster) on the 10-km cycling time, we conducted a simplified model to examine these same factors by the HTR2A genotype. The post hoc analysis excluded HTR2A CT heterozygotes and 2-mg·kg caffeine trials. Among CYP1A2 fast metabolizers alone, a significant difference (1.7 minutes; p = 0.006) was observed when comparing (4- vs. 0-mg·kg caffeine trials) between the HTR2A CC (n = 16; 2.4 minutes) and TT (n = 7; 0.7 minutes) genotypes. Our results show that 4-mg·kg caffeine improves performance in individuals with the HTR2A CC genotype but only in those who are also CYP1A2 AA fast metabolizers. This study was registered with clinicaltrials.gov (NCT02109783).

Effects of caffeine on neuromuscular function in a non-fatigued state and during fatiguing exercise

NEW FINDINGS

What is the central question of the study? What are the effects of caffeine on neuromuscular function in a non-fatigued state and during fatiguing exercise? What is the main finding and its importance? In a non-fatigued state, caffeine decreased the duration of the silent period evoked by transcranial magnetic stimulation. Caffeine-induced reduction of inhibitory mechanisms in the central nervous system before exercise was associated with an increased performance. Individuals who benefit from caffeine ingestion may experience lower perception of effort during exercise and an accelerated recovery of M-wave amplitude postfatigue. This study elucidates the mechanisms of action of caffeine and demonstrates that inter-individual variability of its effects on neuromuscular function is a fruitful area for further work.

ABSTRACT

Caffeine enhances exercise performance, but its mechanisms of action remain unclear. In this study, we investigated its effects on neuromuscular function in a non-fatigued state and during fatiguing exercise. Eighteen men participated in this randomized, double-blind, placebo-controlled crossover trial. Baseline measures included plantarflexion force, drop jump, squat jump, voluntary activation of triceps surae muscle, soleus muscle contractile properties, M-wave, α-motoneuron excitability (H-reflex), corticospinal excitability, short-interval intracortical inhibition, intracortical facilitation, silent period evoked by transcranial magnetic stimulation (SP) and plasma potassium and caffeine concentrations. Immediately after baseline testing, participants ingested caffeine (6 mg·kg^-1 ) or placebo. After a 1-h rest, baseline measures were repeated, followed by a fatiguing stretch-shortening cycle exercise (sets of 40 bilateral rebound jumps on a sledge apparatus) until task failure. Neuromuscular testing was carried out throughout the fatigue protocol and afterwards. Caffeine enhanced drop jump height (by 4.2%) and decreased the SP (by 12.6%) in a non-fatigued state. A caffeine-related decrease in SP and short-interval intracortical inhibition before the fatiguing activity was associated with an increased time to task failure. The participants who benefitted from an improved performance on the caffeine day reported a significantly lower sense of effort during exercise and had an accelerated postexercise recovery of M-wave amplitude. Caffeine modulates inhibitory mechanisms of the CNS, recovery of M-wave amplitude and perception of effort. This study lays the groundwork for future examinations of differences in caffeine-induced neuromuscular changes between those who are deemed to benefit from caffeine ingestion and those who are not.

Sports Supplements: Pearls and Pitfalls

Sports supplements can be generally divided into 3 categories: sports foods (foods/drinks containing macronutrients), medical supplements (vitamins/minerals used to treat deficiencies), and ergogenic supplements (used to benefit performance). Supplements are not regulated by the US Food and Drug Administration. They may get to the market and be contaminated with substances banned in sport or dangerous to health; and the contents may not contain what is listed on the label. When choosing to use a supplement, the safest practice is to choose a certified brand, which tests and authenticates label verification, quality, and lack of contaminants and banned substances for sport.

Supplements and Nutritional Interventions to Augment High-Intensity Interval Training Physiological and Performance Adaptations-A Narrative Review

High-intensity interval training (HIIT) involves short bursts of intense activity interspersed by periods of low-intensity exercise or rest. HIIT is a viable alternative to traditional continuous moderate-intensity endurance training to enhance maximal oxygen uptake and endurance performance. Combining nutritional strategies with HIIT may result in more favorable outcomes. The purpose of this narrative review is to highlight key dietary interventions that may augment adaptations to HIIT, including creatine monohydrate, caffeine, nitrate, sodium bicarbonate, beta-alanine, protein, and essential amino acids, as well as manipulating carbohydrate availability. Nutrient timing and potential sex differences are also discussed. Overall, sodium bicarbonate and nitrates show promise for enhancing HIIT adaptations and performance. Beta-alanine has the potential to increase training volume and intensity and improve HIIT adaptations. Caffeine and creatine have potential benefits, however, longer-term studies are lacking. Presently, there is a lack of evidence supporting high protein diets to augment HIIT. Low carbohydrate training enhances the upregulation of mitochondrial enzymes, however, there does not seem to be a performance advantage, and a periodized approach may be warranted. Lastly, potential sex differences suggest the need for future research to examine sex-specific nutritional strategies in response to HIIT.

Effects of caffeine supplementation on physical performance and mood dimensions in elite and trained-recreational athletes

BACKGROUND

Caffeine supplementation (CAFF) has an established ergogenic effect on physical performance and the psychological response to exercise. However, few studies have compared the response to CAFF intake among athletes of different competition level. This study compares the acute effects of CAFF on anaerobic performance, mood and perceived effort in elite and moderately-trained recreational athletes.

METHODS

Participants for this randomized, controlled, crossover study were 8 elite athletes (in the senior boxing national team) and 10 trained-recreational athletes. Under two experimental conditions, CAFF supplementation (6 mg/kg) or placebo (PLAC), the athletes completed a Wingate test. Subjective exertion during the test was recorded as the rating of perceived exertion (RPE) both at the general level (RPEgeneral) and at the levels muscular (RPEmuscular) and cardiorespiratory (RPEcardio). Before the Wingate test, participants completed the questionnaires Profiles of Moods States (POMS) and Subjective Vitality Scale (SVS).

RESULTS

In response to CAFF intake, improvements were noted in Wpeak (11.22 ± 0.65 vs 10.70 ± 0.84; p = 0.003; [Formula: see text] =0.44), Wavg (8.75 ± 0.55 vs 8.41 0.46; p = 0.001; [Formula: see text] =0.53) and time taken to reach Wpeak (7.56 ± 1.58 vs 9.11 ± 1.53; p <  0.001; [Formula: see text] =0.57) both in the elite and trained-recreational athletes. However, only the elite athletes showed significant increases in tension (+ 325%), vigor (+ 31%) and SVS (+ 28%) scores after the intake of CAFF compared to levels recorded under the condition PLAC (p <  0.05). Similarly, levels of vigor after consuming CAFF were significantly higher in the elite than the trained-recreational athletes (+ 5.8%).

CONCLUSIONS

CAFF supplementation improved anaerobic performance in both the elite and recreational athletes. However, the ergogenic effect of CAFF on several mood dimensions and subjective vitality was greater in the elite athletes.

"I put it in my head that the supplement would help me": Open-placebo improves exercise performance in female cyclists

This study investigated the effect of open-placebo on cycling time-trial (TT) performance. Twenty-eight trained female cyclists completed a 1-km cycling TT following a control session or an open-placebo intervention. The intervention consisted of an individual presentation, provided by a medic, in which the concept of open-placebo was explained to the participant, before she ingested two red and white capsules containing flour; 15 min later, they performed the TT. In the control session, the participant sat quietly for 20 min. Heart rate and ratings of perceived exertion (RPE) were monitored throughout exercise, while blood lactate was determined pre- and post-exercise. Post-exercise questionnaires were employed to gain insight into the perceived influence of the supplement on performance. Open-placebo improved time-to-completion (P = 0.039, 103.6±5.0 vs. 104.4±5.1 s, -0.7±1.8 s, -0.7±1.7%) and mean power output (P = 0.01, 244.8±34.7 vs. 239.7±33.2, +5.1±9.5 W) during the TT. Individual data analysis showed that 11 individuals improved, 13 remained unchanged and 4 worsened their performance with open-placebo. Heart rate, RPE and blood lactate were not different between sessions (all P>0.05). Positive expectation did not appear necessary to induce performance improvements, suggesting unconscious processes occurred, although a lack of an improvement appeared to be associated with a lack of belief. Open-placebo improved 1-km cycling TT performance in trained female cyclists. Although the intervention was successful for some individuals, individual variation was high, and some athletes did not respond or even performed worse. Thus, open-placebo interventions should be carefully considered by coaches and practitioners, while further studies are warranted.

Impact of Caffeine Intake on 800-m Running Performance and Sleep Quality in Trained Runners

Background: Caffeine ingestion improves athletic performance, but impairs sleep quality. We aimed to analyze the effect of caffeine intake on 800-m running performance, sleep quality (SQ), and nocturnal cardiac autonomic activity (CAA) in trained runners. Methods: Fifteen male middle-distance runners participated in the study (aged 23.7 ± 8.2 years). In a randomized and comparative crossover study design, the athletes ingested a placebo (PL) or caffeine supplement (CAF; 6 mg∙kg⁻¹) one hour before an 800-m running time-trial test in the evening. During the night, CAA and SQ were assessed using actigraphy and a sleep questionnaire. A second 800-m running test was performed 24 h after the first. Time, heart rate, rating of perceived exertion, and blood lactate concentration were analyzed for each running test. Results: No significant differences in CAA and performance variables were found between the two conditions. However, CAF impaired sleep efficiency (p = 0.003), actual wake time (p = 0.001), and the number of awakenings (p = 0.005), as measured by actigraphy. Also, CAF impaired the questionnaire variables of SQ (p = 0.005), calm sleep (p = 0.005), ease of falling asleep (p = 0.003), and feeling refreshed after waking (p = 0.006). Conclusion: The supplementation with caffeine (6 mg∙kg⁻¹) did not improve the 800-m running performance, but did impair the SQ of trained runners.

Sports Foods and Dietary Supplements for Optimal Function and Performance Enhancement in Track-and-Field Athletes

Athletes are exposed to numerous nutritional products, attractively marketed with claims of optimizing health, function, and performance. However, there is limited evidence to support many of these claims, and the efficacy and safety of many products is questionable. The variety of nutritional aids considered for use by track-and-field athletes includes sports foods, performance supplements, and therapeutic nutritional aids. Support for sports foods and five evidence-based performance supplements (caffeine, creatine, nitrate/beetroot juice, β-alanine, and bicarbonate) varies according to the event, the specific scenario of use, and the individual athlete's goals and responsiveness. Specific challenges include developing protocols to manage repeated use of performance supplements in multievent or heat-final competitions or the interaction between several products which are used concurrently. Potential disadvantages of supplement use include expense, false expectancy, and the risk of ingesting banned substances sometimes present as contaminants. However, a pragmatic approach to the decision-making process for supplement use is recommended. The authors conclude that it is pertinent for sports foods and nutritional supplements to be considered only where a strong evidence base supports their use as safe, legal, and effective and that such supplements are trialed thoroughly by the individual before committing to use in a competition setting.

Acute caffeine supplementation in combat sports: a systematic review

Caffeine used as a supplement has been shown to improve physical and cognitive performance in several sport modalities due to its effects on the central nervous system. This review assesses the direct effects of caffeine supplementation on performance in combat sports. Using the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guidelines, relevant studies were identified through the Medline, Scopus and SPORTDiscus databases. Of 1053 search results, only 9 articles fulfilled the inclusion criteria. Of these, three studies detected no ergogenic effect of caffeine supplementation, while six studies did observe a significant positive effect. Supplementation with 3-6 mg/kg of caffeine was found to increase the glycolytic contribution to energy metabolism during the execution of real or simulated combats, as indicated by elevated blood lactate concentrations. Caffeine intake was also noted to improve levels of strength, power and upper arm muscular endurance. These effects were not paralleled by an increase in the exertion perceived by the athlete.

The Effect of Acute Caffeine Ingestion on Endurance Performance: A Systematic Review and Meta-Analysis

BACKGROUND

Caffeine is a widely used ergogenic aid with most research suggesting it confers the greatest effects during endurance activities. Despite the growing body of literature around the use of caffeine as an ergogenic aid, there are few recent meta-analyses that quantitatively assess the effect of caffeine on endurance exercise.

OBJECTIVES

To summarise studies that have investigated the ergogenic effects of caffeine on endurance time-trial performance and to quantitatively analyse the results of these studies to gain a better understanding of the magnitude of the ergogenic effect of caffeine on endurance time-trial performance.

METHODS

A systematic review was carried out on randomised placebo-controlled studies investigating the effects of caffeine on endurance performance and a meta-analysis was conducted to determine the ergogenic effect of caffeine on endurance time-trial performance.

RESULTS

Forty-six studies met the inclusion criteria and were included in the meta-analysis. Caffeine has a small but evident effect on endurance performance when taken in moderate doses (3-6 mg/kg) as well as an overall improvement following caffeine compared to placebo in mean power output (3.03 ± 3.07%; effect size = 0.23 ± 0.15) and time-trial completion time (2.22 ± 2.59%; effect size = 0.41 ± 0.2). However, differences in responses to caffeine ingestion have been shown, with two studies reporting slower time-trial performance, while five studies reported lower mean power output during the time-trial.

CONCLUSION

Caffeine can be used effectively as an ergogenic aid when taken in moderate doses, such as during sports when a small increase in endurance performance can lead to significant differences in placements as athletes are often separated by small margins.

ISSN exercise & sports nutrition review update: research & recommendations

Background

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. In the year 2017 alone, 2082 articles were published under the key words ‘sport nutrition’. Consequently, staying current with the relevant literature is often difficult.

Methods

This paper is an ongoing update of the sports nutrition review article originally published as the lead paper to launch the Journal of the International Society of Sports Nutrition in 2004 and updated in 2010. It presents a well-referenced overview of the current state of the science related to optimization of training and performance enhancement through exercise training and nutrition. Notably, due to the accelerated pace and size at which the literature base in this research area grows, the topics discussed will focus on muscle hypertrophy and performance enhancement. As such, this paper provides an overview of: 1.) How ergogenic aids and dietary supplements are defined in terms of governmental regulation and oversight; 2.) How dietary supplements are legally regulated in the United States; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of nutritional approaches to augment skeletal muscle hypertrophy and the potential ergogenic value of various dietary and supplemental approaches.

Conclusions

This updated review is to provide ISSN members and individuals interested in sports nutrition with information that can be implemented in educational, research or practical settings and serve as a foundational basis for determining the efficacy and safety of many common sport nutrition products and their ingredients.

IOC consensus statement: dietary supplements and the high-performance athlete

Nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition programme. Nonetheless, supplement use is widespread at all levels of sport. Products described as supplements target different issues, including (1) the management of micronutrient deficiencies, (2) supply of convenient forms of energy and macronutrients, and (3) provision of direct benefits to performance or (4) indirect benefits such as supporting intense training regimens. The appropriate use of some supplements can benefit the athlete, but others may harm the athlete's health, performance, and/or livelihood and reputation (if an antidoping rule violation results). A complete nutritional assessment should be undertaken before decisions regarding supplement use are made. Supplements claiming to directly or indirectly enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. However, responses are affected by the scenario of use and may vary widely between individuals because of factors that include genetics, the microbiome and habitual diet. Supplements intended to enhance performance should be thoroughly trialled in training or simulated competition before being used in competition. Inadvertent ingestion of substances prohibited under the antidoping codes that govern elite sport is a known risk of taking some supplements. Protection of the athlete's health and awareness of the potential for harm must be paramount; expert professional opinion and assistance is strongly advised before an athlete embarks on supplement use.

IOC Consensus Statement: Dietary Supplements and the High-Performance Athlete

Nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition program. Nonetheless, supplement use is widespread at all levels of sport. Products described as supplements target different issues, including the management of micronutrient deficiencies, supply of convenient forms of energy and macronutrients, and provision of direct benefits to performance or indirect benefits such as supporting intense training regimens. The appropriate use of some supplements can offer benefits to the athlete, but others may be harmful to the athlete's health, performance, and/or livelihood and reputation if an anti-doping rule violation results. A complete nutritional assessment should be undertaken before decisions regarding supplement use are made. Supplements claiming to directly or indirectly enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. However, responses are affected by the scenario of use and may vary widely between individuals because of factors that include genetics, the microbiome, and habitual diet. Supplements intended to enhance performance should be thoroughly trialed in training or simulated competition before implementation in competition. Inadvertent ingestion of substances prohibited under the anti-doping codes that govern elite sport is a known risk of taking some supplements. Protection of the athlete's health and awareness of the potential for harm must be paramount, and expert professional opinion and assistance is strongly advised before embarking on supplement use.

Evidence-Based Supplements for the Enhancement of Athletic Performance

A strong foundation in physical conditioning and sport-specific experience, in addition to a bespoke and periodized training and nutrition program, are essential for athlete development. Once these underpinning factors are accounted for, and the athlete reaches a training maturity and competition level where marginal gains determine success, a role may exist for the use of evidence-based performance supplements. However, it is important that any decisions surrounding performance supplements are made in consideration of robust information that suggests the use of a product is safe, legal, and effective. The following review focuses on the current evidence-base for a number of common (and emerging) performance supplements used in sport. The supplements discussed here are separated into three categories based on the level of evidence supporting their use for enhancing sports performance: (1) established (caffeine, creatine, nitrate, beta-alanine, bicarbonate); (2) equivocal (citrate, phosphate, carnitine); and (3) developing. Within each section, the relevant performance type, the potential mechanisms of action, and the most common protocols used in the supplement dosing schedule are summarized.

Caffeine and Bicarbonate for Speed. A Meta-Analysis of Legal Supplements Potential for Improving Intense Endurance Exercise Performance

A 1% change in average speed is enough to affect medal rankings in intense Olympic endurance events lasting ~45 s to 8 min which for example includes 100 m swimming and 400 m running (~1 min), 1,500 m running and 4000 m track cycling (~4 min) and 2,000 m rowing (~6-8 min). To maximize the likelihood of winning, athletes utilizes legal supplements with or without scientifically documented beneficial effects on performance. Therefore, a continued systematic evidence based evaluation of the possible ergogenic effects is of high importance. A meta-analysis was conducted with a strict focus on closed-end performance tests in humans in the time domain from 45 s to 8 min. These test include time-trials or total work done in a given time. This selection criterion results in a high relevance for athletic performance. Only peer-reviewed placebo controlled studies were included. The often applied and potentially ergogenic supplements beta-alanine, bicarbonate, caffeine and nitrate were selected for analysis. Following a systematic search in Pubmed and SportsDiscuss combined with evaluation of cross references a total of 7 (beta-alanine), 25 (bicarbonate), 9 (caffeine), and 5 (nitrate) studies was included in the meta-analysis. For each study, performance was converted to an average speed (km/h) from which an effect size (ES; Cohens d with 95% confidence intervals) was calculated. A small effect and significant performance improvement relative to placebo was observed for caffeine (ES: 0.41 [0.15–0.68], P = 0.002) and bicarbonate (ES: 0.40 [0.27–0.54], P < 0.001). Trivial and non-significant effects on performance was observed for nitrate (ES: 0.19 [−0.03–0.40], P = 0.09) and beta-alanine (ES: 0.17 [−0.12–0.46], P = 0.24). Thus, caffeine's and bicarbonate's ergogenic effect is clearly documented for intense endurance performance. Importantly, for all supplements an individualized approach may improve the ergogenic effect on performance.

Effects of Coffee and Caffeine Anhydrous Intake During Creatine Loading

The purpose of this study was to determine the effect of 5 days of creatine (CRE) loading alone or in combination with caffeine anhydrous (CAF) or coffee (COF) on upper-body and lower-body strength and sprint performance. Physically active males (n = 54; mean ± SD; age = 20.1 ± 2.1 years; weight = 78.8 ± 8.8 kg) completed baseline testing, consisting of 1 repetition maximum (1RM) and repetitions to fatigue with 80% 1RM for bench press and leg press, followed by a repeated sprint test of five, 10-second sprints separated by 60-second rest on a cycle ergometer to determine peak power (PP) and total power (TP). At least 72 hours later, subjects were randomly assigned to supplement with CRE (5 g of CRE monohydrate, 4 times per day; n = 14), CRE + CAF (CRE +300 mg·d of CAF; n = 13), CRE + COF (CRE +8.9 g of COF, yielding 303 mg of CAF; n = 13), or placebo (PLA; n = 14) for 5 days. Serum creatinine (CRN) was measured before and after supplementation, and on day 6, participants repeated pretesting procedures. Strength measures were improved in all groups (p ≤ 0.05), with no significant time × treatment interactions. No significant interaction or main effects were observed for PP. For TP, a time × sprint interaction was observed (p ≤ 0.05), with no significant interactions among treatment groups. A time × treatment interaction was observed for serum CRN values (p ≤ 0.05) that showed increases in all groups except PLA. Four subjects reported mild gastrointestinal discomfort with CRE + CAF, with no side effects reported in other groups. These findings suggest that neither CRE alone nor in combination with CAF or COF significantly affected performance compared with PLA.

Effect of Environmental and Feedback Interventions on Pacing Profiles in Cycling: A Meta-Analysis

In search of their optimal performance athletes will alter their pacing strategy according to intrinsic and extrinsic physiological, psychological and environmental factors. However, the effect of some of these variables on pacing and exercise performance remains somewhat unclear. Therefore, the aim of this meta-analysis was to provide an overview as to how manipulation of different extrinsic factors affects pacing strategy and exercise performance. Only self-paced exercise studies that provided control and intervention group(s), reported trial variance for power output, disclosed the type of feedback received or withheld, and where time-trial power output data could be segmented into start, middle and end sections; were included in the meta-analysis. Studies with similar themes were grouped together to determine the mean difference (MD) with 95% confidence intervals (CIs) between control and intervention trials for: hypoxia, hyperoxia, heat-stress, pre-cooling, and various forms of feedback. A total of 26 studies with cycling as the exercise modality were included in the meta-analysis. Of these, four studies manipulated oxygen availability, eleven manipulated heat-stress, four implemented pre-cooling interventions and seven studies manipulated various forms of feedback. Mean power output (MPO) was significantly reduced in the middle and end sections (p < 0.05), but not the start section of hypoxia and heat-stress trials compared to the control trials. In contrast, there was no significant change in trial or section MPO for hyperoxic or pre-cooling conditions compared to the control condition (p > 0.05). Negative feedback improved overall trial MPO and MPO in the middle section of trials (p < 0.05), while informed feedback improved overall trial MPO (p < 0.05). However, positive, neutral and no feedback had no significant effect on overall trial or section MPO (p > 0.05). The available data suggests exercise regulation in hypoxia and heat-stress is delayed in the start section of trials, before significant reductions in MPO occur in the middle and end of the trial. Additionally, negative feedback involving performance deception may afford an upward shift in MPO in the middle section of the trial improving overall performance. Finally, performance improvements can be retained when participants are informed of the deception.

Time of Day and Training Status Both Impact the Efficacy of Caffeine for Short Duration Cycling Performance

This project was designed to assess the effects of time of day and training status on the benefits of caffeine supplementation for cycling performance. Twenty male subjects (Age, 25 years; Peak oxygen consumption, 57 mL·kg⁻¹·min⁻¹) were divided into tertiles based on training levels, with top and bottom tertiles designated as ‘trained’ (n = 7) and ‘untrained’ (n = 7). Subjects completed two familiarization trials and four experimental trials consisting of a computer-simulated 3-km cycling time trial (TT). The trials were performed in randomized order for each combination of time of day (morning and evening) and treatment (6mg/kg of caffeine or placebo). Magnitude-based inferences were used to evaluate all treatment effects. For all subjects, caffeine enhanced TT performance in the morning (2.3% ± 1.7%, ‘very likely’) and evening (1.4% ± 1.1%, ‘likely’). Both untrained and trained subjects improved performance with caffeine supplementation in the morning (5.5% ± 4.3%, ‘likely’; 1.0% ± 1.7%, ‘likely’, respectively), but only untrained subjects rode faster in the evening (2.9% ± 2.6%, ‘likely’). Altogether, our observations indicate that trained athletes are more likely to derive ergogenic effects from caffeine in the morning than the evening. Further, untrained individuals appear to receive larger gains from caffeine in the evening than their trained counterparts.

Coffee and Caffeine Ingestion Have Little Effect on Repeated Sprint Cycling in Relatively Untrained Males

The present study investigated the effect of ingesting caffeine-dose-matched anhydrous caffeine or coffee on the performance of repeated sprints. Twelve recreationally active males (mean ± SD age: 22 ± 2 years, height: 1.78 ± 0.07 m, body mass: 81 ± 16 kg) completed eighteen 4 s sprints with 116 s recovery on a cycle ergometer on four separate occasions in a double-blind, randomised, counterbalanced crossover design. Participants ingested either 3 mg·kg⁻¹ of caffeine (CAF), 0.09 g·kg⁻¹ coffee, which provided 3 mg·kg⁻¹ of caffeine (COF), a taste-matched placebo beverage (PLA), or a control condition (CON) 45 min prior to commencing the exercise protocol. Peak and mean power output and rating of perceived exertion (RPE) were recorded for each sprint. There were no significant differences in peak power output (CAF: 949 ± 199 W, COF: 949 ± 174 W, PLA: 971 ± 149 W and CON: 975 ± 170 W; p = 0.872; ηP2 = 0.02) or mean power output (CAF: 873 ± 172 W, COF: 862 ± 44 W, PLA: 887 ± 119 W and CON: 892 ± 143 W; p = 0.819; ηP2 = 0.03) between experimental conditions. Mean RPE was similar for all trials (CAF: 11 ± 2, COF: 11 ± 2, PLA: 11 ± 2 and CON: 11 ± 2; p = 0.927; ηP2 = 0.01). Neither the ingestion of COF or CAF improved repeated sprint cycling performance in relatively untrained males.

Caffeine ingestion improves power output decrement during 3-min all-out exercise

PURPOSE

To investigate the effect of caffeine ingestion on the 3-min all-out test (3MT) performance and plasma electrolytes in athletes.

METHODS

Fifteen collegiate male basketball players were recruited and completed two trials separated by at least 1 week in caffeine (CAF, 6 mg kg(-1)) and placebo conditions. During the first visit, participants performed an incremental cycling test to determine their 3MT resistance. After a familiarization trial, participants performed a CAF or PL trial according to a randomized crossover design. One hour after ingesting capsules, the participants performed the 3MT to estimate the end-test power (EP) and work done above EP (WEP). Blood samples for sodium (Na(+)), potassium (K(+)), pH, and lactate concentrations were drawn pretest, 1 h after ingestion, and posttest.

RESULTS

Significant differences in WEP (CAF vs. PL, 13.4 ± 3.0 vs. 12.1 ± 2.7 kJ, P < 0.05) but not in EP (CAF vs. PL, 242 ± 37 vs. 244 ± 42 W, P > 0.05) were determined between the conditions. Compared with the PL condition, the CAF condition yielded significantly higher power outputs (60-150 s), a lower fatigue rate during the 3MT (CAF vs. PL, 0.024 ± 0.007 vs. 0.029 ± 0.006 s(-1), P < 0.05), a significantly higher lactate concentration after the 3MT, and significantly lower K(+) concentrations at 1 h after caffeine ingestion. There were no significant interaction effects for pH and Na(+) concentrations.

CONCLUSIONS

Caffeine ingestion did not change EP but improved WEP and the rate of decline in power output during short-term, severe exercise.

The acute effects of multi-ingredient pre-workout ingestion on strength performance, lower body power, and anaerobic capacity

Background

Multi-ingredient pre-workout supplements (MIPS) are popular among resistance trained individuals. Previous research has indicated that acute MIPS ingestion may increase muscular endurance when using a hypertrophy-based protocol but less is known in regard to their effects on strength performance and high intensity running capacity. Therefore, the purpose was to determine if short-term, MIPS ingestion influences strength performance and anaerobic running capacity.

Methods

In a double-blind, randomized, placebo controlled, crossover design; 12 males (19 ± 1 yrs.; 180 ± 12 cm; 89.3 ± 11 kg; 13.6 ± 4.9 %BF) had their body composition assessed followed by 5-repetition maximum (5RM) determination of back squat (BS; 119.3 ± 17.7 kg) and bench press (BP; 92.1 ± 17.8 kg) exercises. On two separate occasions subjects ingested a MIPS or a placebo (P) 30-minutes prior to performing a counter movement vertical jump test, 5 sets of 5 repetitions at 85 % of 5RM of BS and BP, followed by a single set to failure, and an anaerobic capacity sprint test to assess peak and mean power. Subjective markers of energy levels and fatigue were also assessed. Subjects returned one week later for a second testing session using counter treatment.

Results

MIPS resulted in a greater number of repetitions performed in the final set to failure in the BP (MIPS, 9.8 ± 1.7 repetitions; P, 9.1 ± 2; p = 0.03, d = 0.38), which led to a greater total volume load (set x repetitions x load) in the MIPS (753 ± 211 kg) compared to P (710 ± 226 kg; p =0.03, d = .20). MIPS ingestion improved subjective markers of fatigue (p = 0.01, d = 3.78) and alertness (p = 0.048, d = 2.72) following a bout of resistance training. An increase in mean power was observed in the MIPS condition (p = 0.03, d = 0.25) during the anaerobic sprint test.

Conclusion

Results suggest that acute ingestion of a MIPS study may increase upper body muscular endurance. In addition, acute MIPS ingestion improved mean power output during an anaerobic capacity sprint test. However, the practical significance of these performance related outcomes may be minimal due to the small effect sizes observed. MIPS ingestion does appear to positively influence subjective markers of fatigue and alertness during high-intensity exercise.

Effects of training-induced fatigue on pacing patterns in 40-km cycling time trials

INTRODUCTION

In some endurance sports, athletes complete several competitions within a short period, resulting in accumulated fatigue. It is unclear whether fatigued athletes choose the same pacing pattern (PP) as when they have recovered.

PURPOSE

This study aimed to analyze effects of fatigue on PP of cyclists during a 40-km time trial (TT).

METHODS

Twenty-three male cyclists (28.8 ± 7.6 yr) completed three 40-km TT on a cycle ergometer. TT were conducted before (TT1) and after (TT2) a 6-d training period. A third TT was carried out after 72 h of recovery (TT3). Training days consisted of two cycling sessions: mornings, 1 h at 95% of lactate threshold or 3 × 5 × 30 s all-out sprint; afternoons, 3 h at 80% individual anaerobic threshold. Four-kilometer split times (min) and RPE were recorded during TT.

RESULTS

Performance decreased from TT1 to TT2 (65.7 ± 3.5 vs 66.7 ± 3.3 min; P < 0.05) and increased from TT2 to TT3 (66.7 ± 3.3 vs 65.5 ± 3.3 min; P < 0.01). PP showed a significant difference between TT1 and TT2 (P < 0.001) as well as between TT2 and TT3 (P < 0.01). PP in TT1 and TT3 showed no significant difference (P > 0.05). In TT1 and TT3, cyclists started faster in the first 4 km compared with TT2. RPE course showed no significant difference between TT (P > 0.05).

CONCLUSIONS

Fatigue reversibly changes the PP of cyclists during a 40-km TT. Participants reduced their power output until premature exhaustion seemed very unlikely. This supports the assumption that pacing includes a combination of anticipation and feedback mechanisms.

Effects of coffee and caffeine anhydrous on strength and sprint performance

Caffeine and coffee are widely used among active individuals to enhance performance. The purpose of the current study was to compare the effects of acute coffee (COF) and caffeine anhydrous (CAF) intake on strength and sprint performance. Fifty-four resistance-trained males completed strength testing, consisting of one-rep max (1RM) and repetitions to fatigue (RTF) at 80% of 1RM for leg press (LP) and bench press (BP). Participants then completed five, 10-second cycle ergometer sprints separated by one minute of rest. Peak power (PP) and total work (TW) were recorded for each sprint. At least 48 hours later, participants returned and ingested a beverage containing CAF (300 mg flat dose; yielding 3-5 mg/kg bodyweight), COF (8.9 g; 303 mg caffeine), or placebo (PLA; 3.8 g non-caloric flavouring) 30 minutes before testing. LP 1RM was improved more by COF than CAF (p = .04), but not PLA (p = .99). Significant interactions were not observed for BP 1RM, BP RTF, or LP RTF (p > .05). There were no sprint × treatment interactions for PP or TW (p > .05). 95% confidence intervals revealed a significant improvement in sprint 1 TW for CAF, but not COF or PLA. For PLA, significant reductions were observed in sprint 4 PP, sprint 2 TW, sprint 4 TW, and average TW; significant reductions were not observed with CAF or COF. Neither COF nor CAF improved strength outcomes more than PLA, while both groups attenuated sprint power reductions to a similar degree. Coffee and caffeine anhydrous may be considered suitable pre-exercise caffeine sources for high-intensity exercise.

Acute consumption of a caffeinated energy drink enhances aspects of performance in sprint swimmers

This study investigated the effect of a caffeinated energy drink on various aspects of performance in sprint swimmers. In a randomised and counterbalanced order, fourteen male sprint swimmers performed two acute experimental trials after the ingestion of a caffeinated energy drink (3 mg/kg) or after the ingestion of the same energy drink without caffeine (0 mg/kg; placebo). After 60 min of ingestion of the beverages, the swimmers performed a countermovement jump, a maximal handgrip test, a 50 m simulated competition and a 45 s swim at maximal intensity in a swim ergometer. A blood sample was withdrawn 1 min after the completion of the ergometer test. In comparison with the placebo drink, the intake of the caffeinated energy drink increased the height in the countermovement jump (49.4 (SD 5.3) v. 50.9 (SD 5.2) cm, respectively; P<0.05) and maximal force during the handgrip test with the right hand (481 (SD 49) v. 498 (SD 43) N; P<0.05). Furthermore, the caffeinated energy drink reduced the time needed to complete the 50 m simulated swimming competition (27.8 (SD 3.4) v. 27.5 (SD 3.2) s; P<0.05), and it increased peak power (273 (SD 55) v. 303 (SD 49) W; P <0.05) and blood lactate concentration (11.0 (SD 2.0) v. 11.7 (SD 2.1) mM; P<0.05) during the ergometer test. The caffeinated energy drink did not modify the prevalence of insomnia (7 v. 7%), muscle pain (36 v. 36%) or headache (0 v. 7%) during the hours following its ingestion (P>0.05). A caffeinated energy drink increased some aspects of swimming performance in competitive sprinters, whereas the side effects derived from the intake of this beverage were marginal at this dosage.

Performance effects and metabolic consequences of caffeine and caffeinated energy drink consumption on glucose disposal

This review documents two opposing effects of caffeine and caffeine-containing energy drinks, i.e., their positive effects on athletic performance and their negative impacts on glucose tolerance in the sedentary state. Analysis of studies examining caffeine administration prior to performance-based exercise showed caffeine improved completion time by 3.6%. Similar analyses following consumption of caffeine-containing energy drinks yielded positive, but more varied, benefits, which were likely due to the diverse nature of the studies performed, the highly variable composition of the beverages consumed, and the range of caffeine doses administered. Conversely, analyses of studies administering caffeine prior to either an oral glucose tolerance test or insulin clamp showed a decline in whole-body glucose disposal of ~30%. The consequences of this resistance are unknown, but there may be implications for the development of a number of chronic diseases. Both caffeine-induced performance enhancement and insulin resistance converge with the primary actions of caffeine on skeletal muscle.

The efficacy of acute nutritional interventions on soccer skill performance

BACKGROUND

The use of nutritional ergogenic aids in team sports such as soccer is now commonplace. Aligned with the primary aim of soccer, which is to score more goals than the opposition within the allotted time, the quality of performance of technical actions (i.e., skills) executed during soccer-specific exercise is likely to determine success. However, when seeking to maintain soccer skill performance, information about the efficacy of nutritional interventions is lacking and factors which might modulate the efficacy of such strategies are unclear.

OBJECTIVE

This review aimed (i) to systematically evaluate the current research that examines the efficacy of nutritional interventions on soccer skills, and (ii) to provide a qualitative commentary on factors that have the potential to modulate the efficacy of such strategies.

DATA SOURCES

Relevant databases (PubMed and SPORTDiscus) were searched up to and including 1 July, 2013 for studies that investigated the efficacy of acute nutritional interventions on soccer skill performances.

STUDY SELECTION

Overall, 279 records were retrieved. Articles were sequentially excluded from the review based on specific criteria, being: (A) articles that did not report outcomes directly relating to skilled performances in soccer, (B) articles that examined the influence of interventions that were not nutritional in origin and/or were nutritional in origin but provided >3 hours before skill testing commenced, (C) articles that were review papers, and (D) post-acceptance withdrawal of articles methods from database.

STUDY APPRAISAL AND SYNTHESIS METHODS

Articles were independently assessed for the quality of the methods employed based upon the Physiotherapy Evidence Database (PEDro) scale. Records achieving a minimum PEDro score of 5 out of 10 were included in this review. Qualitative appraisal of 13 articles was performed after the application of exclusion criteria and quality assurance processes. The majority (n = 8) of articles examined the influence of carbohydrates on technical performance whereas fewer studies investigated the influence of caffeine ingestion (n = 2) and fluid provision (n = 3).

RESULTS

Findings were reported for a total of 171 participants and all but one of the included articles used cross-over study designs. Most participants (94 %) were male, highly trained (reported maximal aerobic capacity range 50-59 ml·kg(-1)·min(-1)) and exercised in temperate environments (reported temperature range 13-25 °C). Six of the eight studies reported that carbohydrates, consumed in the form of a 6-8 % solution of glucose, sucrose or maltodextrin at rates of 30-60 g·h(-1), enhanced at least one aspect of skilled performance over the duration of exercise (75-90 min). Although some evidence exists to support the consumption of caffeine (6 mg·kg(-1) body mass [BM]) and prescribed fluid to preserve skills performed during soccer-specific exercise, findings from the small number of included studies were inconsistent.

LIMITATIONS

The outcome measures and methods used to quantify skilled performance were not consistent across studies; consequently, it was not possible to perform meta-analyses to produce pooled effect sizes in this review.

CONCLUSIONS

The findings from this systematic review suggest that nutritional interventions, which provide carbohydrate, caffeine and fluid, have potential to preserve skills performed under conditions that induce soccer-specific fatigue. The weight of current evidence supports the consumption of carbohydrate, but is less conclusive with respect to caffeine and fluid provision. It is likely that the efficacy of a nutritional intervention will be modulated by factors including the dose consumed, the mode of administration, individual responsiveness to the intervention and interactions with other physiological changes occurring during soccer-specific exercise. Consequently, these factors should be considered when using carbohydrates, caffeine and fluid provision to maintain skilled performances in soccer. Future research should seek to optimise the nutritional strategies employed to maintain technical performance throughout match-play.

Exercise and sport performance with low doses of caffeine

Caffeine is a popular work-enhancing supplement that has been actively researched since the 1970s. The majority of research has examined the effects of moderate to high caffeine doses (5-13 mg/kg body mass) on exercise and sport. These caffeine doses have profound effects on the responses to exercise at the whole-body level and are associated with variable results and some undesirable side effects. Low doses of caffeine (<3 mg/kg body mass, ~200 mg) are also ergogenic in some exercise and sport situations, although this has been less well studied. Lower caffeine doses (1) do not alter the peripheral whole-body responses to exercise; (2) improve vigilance, alertness, and mood and cognitive processes during and after exercise; and (3) are associated with few, if any, side effects. Therefore, the ergogenic effect of low caffeine doses appears to result from alterations in the central nervous system. However, several aspects of consuming low doses of caffeine remain unresolved and suffer from a paucity of research, including the potential effects on high-intensity sprint and burst activities. The responses to low doses of caffeine are also variable and athletes need to determine whether the ingestion of ~200 mg of caffeine before and/or during training and competitions is ergogenic on an individual basis.

Caffeine ingestion after rapid weight loss in judo athletes reduces perceived effort and increases plasma lactate concentration without improving performance

The objective of this study was to examine the effect of caffeine on judo performance, perceived exertion, and plasma lactate response when ingested during recovery from a 5-day weight loss period. Six judokas performed two cycles of a 5-day rapid weight loss procedure to reduce their body weight by ~5%. After weigh-in, subjects re-fed and rehydrated over a 4-h recovery period. In the third hour of this "loading period", subjects ingested a capsule containing either caffeine (6 mg·kg-1) or placebo. One hour later, participants performed three bouts of a judo fitness test with 5-min recovery periods. Perceived exertion and plasma lactate were measured before and immediately after each test bout. Body weight was reduced in both caffeine and placebo conditions after the weight loss period (-3.9% ± 1.6% and -4.0% ± 2.3% from control, respectively, p < 0.05). At three hours after weigh-in, body weight had increased with both treatments but remained below the control (-3.0% ± 1.3% and -2.7% ± 2.2%). There were no significant differences in the number of throws between the control, caffeine or placebo groups. However, plasma lactate was systemically higher and perceived exertion lower in the subjects who ingested caffeine compared to either the control or placebo subjects (p < 0.05). In conclusion, caffeine did not improve performance during the judo fitness test after a 5-day weight loss period, but reduced perceived exertion and increased plasma lactate.

A systematic review of the efficacy of ergogenic aids for improving running performance

Running is a common form of activity worldwide, and participants range from "weekend warriors" to Olympians. Unfortunately, few studies have examined efficacy of various ergogenic aids in runners because the majority of the literature consists of cycling-based protocols, which do not relate to running performance. The majority of running studies conducted markedly vary in regards to specific distance completed, subject fitness level, and effectiveness of the ergogenic aid examined. The aim of this article was to systematically examine the literature concerning utility of several ergogenic aids on middle-distance running (400-5,000 m) and long-distance running (10,000 meters marathon = 42.2 km) performance. In addition, this article highlights the dearth of running-specific studies in the literature and addresses recommendations for future research to optimize running performance through nutritional intervention. Results revealed 23 studies examining effects of various ergogenic aids on running performance, with a mean Physiotherapy Evidence Database score equal to 7.85 ± 0.70. Of these studies, 71% (n = 15) demonstrated improved running performance with ergogenic aid ingestion when compared with a placebo trial. The most effective ergogenic aids for distances from 400 m to 40 km included sodium bicarbonate (4 studies; 1.5 ± 1.1% improvement), sodium citrate (6 studies; 0.3 ± 1.7% improvement), caffeine (CAFF) (7 studies; 1.1 ± 0.4% improvement), and carbohydrate (CHO) (6 studies; 4.1 ± 4.4% improvement). Therefore, runners may benefit from ingestion of sodium bicarbonate to enhance middle distance performance and caffeine and carbohydrate to enhance performance at multiple distances.

Caffeine alters anaerobic distribution and pacing during a 4000-m cycling time trial

The purpose of the present study was to investigate the effects of caffeine ingestion on pacing strategy and energy expenditure during a 4000-m cycling time-trial (TT). Eight recreationally-trained male cyclists volunteered and performed a maximal incremental test and a familiarization test on their first and second visits, respectively. On the third and fourth visits, the participants performed a 4000-m cycling TT after ingesting capsules containing either caffeine (5 mg.kg⁻¹ of body weight, CAF) or cellulose (PLA). The tests were applied in a double-blind, randomized, repeated-measures, cross-over design. When compared to PLA, CAF ingestion increased mean power output [219.1±18.6 vs. 232.8±21.4 W; effect size (ES)  = 0.60 (95% CI = 0.05 to 1.16), p = 0.034] and reduced the total time [419±13 vs. 409±12 s; ES = −0.71 (95% CI = −0.09 to −1.13), p = 0.026]. Furthermore, anaerobic contribution during the 2200-, 2400-, and 2600-m intervals was significantly greater in CAF than in PLA (p<0.05). However, the mean anaerobic [64.9±20.1 vs. 57.3±17.5 W] and aerobic [167.9±4.3 vs. 161.8±11.2 W] contributions were similar between conditions (p>0.05). Similarly, there were no significant differences between CAF and PLA for anaerobic work (26363±7361 vs. 23888±6795 J), aerobic work (68709±2118 vs. 67739±3912 J), or total work (95245±8593 vs. 91789±7709 J), respectively. There was no difference for integrated electromyography, blood lactate concentration, heart rate, and ratings of perceived exertion between the conditions. These results suggest that caffeine increases the anaerobic contribution in the middle of the time trial, resulting in enhanced overall performance.

Caffeine increases anaerobic work and restores cycling performance following a protocol designed to lower endogenous carbohydrate availability

The purpose this study was to examine the effects of caffeine ingestion on performance and energy expenditure (anaerobic and aerobic contribution) during a 4-km cycling time trial (TT) performed after a carbohydrate (CHO) availability-lowering exercise protocol. After preliminary and familiarization trials, seven amateur cyclists performed three 4-km cycling TT in a double-blind, randomized and crossover design. The trials were performed either after no previous exercise (CON), or after a CHO availability-lowering exercise protocol (DEP) performed in the previous evening, followed by either placebo (DEP-PLA) or 5 mg.kg(-1) of caffeine intake (DEP-CAF) 1 hour before the trial. Performance was reduced (-2.1%) in DEP-PLA vs CON (421.0±12.3 vs 412.4±9.7 s). However, performance was restored in DEP-CAF (404.6±17.1 s) compared with DEP-PLA, while no differences were found between DEP-CAF and CON. The anaerobic contribution was increased in DEP-CAF compared with both DEP-PLA and CON (67.4±14.91, 47. 3±14.6 and 55.3±14.0 W, respectively), and this was more pronounced in the first 3 km of the trial. Similarly, total anaerobic work was higher in DEP-CAF than in the other conditions. The integrated electromyographic activity, plasma lactate concentration, oxygen uptake, aerobic contribution and total aerobic work were not different between the conditions. The reduction in performance associated with low CHO availability is reversed with caffeine ingestion due to a higher anaerobic contribution, suggesting that caffeine could access an anaerobic "reserve" that is not used under normal conditions.

Effects of isolated locomotor muscle fatigue on pacing and time trial performance

PURPOSE

Locomotor muscle fatigue impairs exercise performance during time to exhaustion tests. However, its effect on self-regulation of power output (pacing) is unknown. The primary aim of this study was to investigate the effects of locomotor muscle fatigue on pacing and time trial performance.

METHODS

Ten healthy recreationally active men completed a 15-min time trial on a cycle ergometer 30 min after undergoing an eccentric fatiguing protocol designed to induce a substantial strength loss in the knee extensor muscles without inducing significant metabolic stress. This fatigue condition was compared with a control condition, using a randomly counterbalanced AB/BA crossover design.

RESULTS

Total work completed during the 15-min cycling time trial was significantly reduced by 4.8 % in the fatigue condition compared with the control condition. This was caused by a significant reduction in power output. Rating of perceived exertion was significantly higher in the fatigue condition compared with the control condition only during the first 3 min of the time trial. Heart rate and vastus lateralis integrated electromyogram were not significantly different between the two conditions.

CONCLUSION

The results show that participants with fatigued locomotor muscles reduce their pace but do not change their pacing strategy. As a result, there was a significant reduction in time trial performance. As predicted by the psychobiological model of exercise performance, a slower pace may be a behavioral response to compensate for the significant increase in perception of effort induced by locomotor muscle fatigue.

Efeito da ingestão de cafeína no desempenho em corrida de 200 metros rasos

O objetivo do estudo foi analisar a influência da cafeína no desempenho dos 200 metros rasos (200 m). Dezessete indivíduos fisicamente ativos (21,5 ± 2,15 anos; 175,9 ± 5,5 cm; 74,1 ± 10,04 kg) executaram em dias diferentes duas performances de 200m. Uma hora antes do teste foi ingerido de modo duplo-cego e randomizado cápsula gelatinosa contendo cafeína (6mg.kg-1) ou placebo. Foram analisados o tempo final dos 200 m rasos e o lactato sanguíneo ([La]; repouso, pré-aquecimento e pós-teste). A ingestão de cafeína diminuiu significantemente o tempo no desempenho dos 200m em relação ao placebo (27,398 ± 1,626 vs. 27,596 ± 1,714 s, respectivamente) e aumentou as [La] pré-aquecimento (1,236 ± 0,497 vs 1,064 ± 0,330 mM) sem modificações na [La] pico. Assim, podemos concluir que a ingestão de cafeína exerceu efeito ergogênico no desempenho com característica anaeróbia, nos indivíduos ativos avaliados neste estudo. Contudo a ausência de modificação na [La] pico indica que essa melhora não parece estar relacionada a um maior fluxo glicolítico.

Acute and chronic caffeine administration increases physical activity in sedentary adults

Caffeine is a commonly used stimulant thought to have ergogenic properties. Most studies on the ergogenic effects of caffeine have been conducted in athletes. The purpose of this study was to test the hypothesis that caffeine reduces ratings of perceived exertion and increases liking of physical activity in sedentary adults. Participants completed treadmill walking at 60% to 70% of their maximal heart rate at baseline and for 6 subsequent visits, during which half of the participants were given caffeine (3 mg/kg) and half given placebo in a sports drink vehicle. To investigate the potential synergistic effects of acute and chronic caffeine on self-determined exercise duration, participants were rerandomized to either the same or different condition for the last visit, creating 4 chronic/acute treatment groups (placebo/placebo, placebo/caffeine, caffeine/placebo, caffeine/caffeine). Participants rated how much they liked the activity and perceived exertion at each visit. There was a main effect of time on liking of physical activity, with liking increasing over time and an interaction of sex and caffeine treatment on liking, with liking of activity increasing in female participants treated with caffeine, but not with placebo. There was no effect of caffeine on ratings of perceived exertion. Individuals who received caffeine on the final test day exercised for significantly longer than those who received placebo. These data suggest that repeated exposure to physical activity significantly increases liking of exercise and reduces ratings of perceived exertion and that caffeine does little to further modify these effects.