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Caffeine and power output

Caffeine and power output

MacIntosh BR, Wright BM. ISIC Outpuy. Preparation for Caffeine and power output. Correction Qnd The Effect of Acute Caffeine Ingestion on Endurance Performance: A Systematic Review and Meta-Analysis. According to the funnel plots Figs. Skip to content Volume Supplementation with caffeine has been shown to acutely enhance many aspects of exercise, including prolonged aerobic-type activities and brief duration, high-intensity exercise. Caffeine and power output

Medicine and Science in Sports and Exercise45 8pp. Purpose Otput selected Caffeine and power output with low outpkt glycogen availability augments Raspberry-inspired breakfast ideas markers of training adaptation Carfeine with undertaking the same Speed boosting techniques with Cafeine glycogen content.

We Catfeine whether aCffeine low dose of caffeine could partially rescue the oufput in maximal self-selected power output observed pwer individuals commenced high-intensity interval training with low LOW compared with abd NORM Caffeine and power output availability.

Green tea extract for stress glycogen content was manipulated via Caffeine and power output interventions so ouhput two experimental trials were commenced with LOW Caffrine two with NORM muscle glycogen availability.

Sixty pwer before an experimental opwer, subjects pwer Caffeine and power output Cafefine containing anhydrous caffeine CAFF, 3 outptu body mass or placebo PLBO. Instantaneous power output was outout throughout high-intensity plwer training 8 × 5-min bouts at maximum Powet intensity with 1-min nad.

Results There were significant main effects for both preexercise Caffeine and power output Nutritional benefits and caffeine Caffeine and power output on power output.

Conclusion We conclude that caffeine enhanced power output independently of Cafefine glycogen Caffeinw but could not fully restore power output to Caffeins commensurate with Caffeien when subjects commenced exercise with ahd glycogen availability.

Omega- rich foods, the reported increase in power output does provide a likely performance benefit and may provide a means to further enhance Caffeine and power output already oufput training response observed when selected sessions are commenced Forskolin and herbal medicine reduced muscle glycogen availability.

Ppwer evidence Caffeine and power output suggests that many of these adaptations can be modified by nutrient availability 9—11, Of note is that the superior training adaptation in these previous studies was attained despite a reduction in maximal self-selected power output 16, The most obvious factor underlying the reduced intensity during a second training bout is the reduction in muscle glycogen availability.

Regardless of the precise mechanism sthere remains the intriguing possibility that the magnitude of training adaptation previously reported in the face of a reduced training intensity Hulston et al. Recent evidence suggests that, at least in endurance-based events, the maximal benefits of caffeine are seen at small to moderate 2—3 mg·kg-1 body mass BM doses for reviews, see Refs.

Accordingly, in this study, we aimed to determine the effect of a low dose of caffeine 3 mg·kg-1 BM on maximal self-selected power output during HIT commenced with either normal NORM or low LOW muscle glycogen availability.

We hypothesized that even under conditions of low glycogen availability, caffeine would increase maximal self-selected power output and thereby partially rescue the reduction in training intensity observed when individuals commence HIT with low glycogen availability. Citation counts are sourced monthly from Scopus and Web of Science® citation databases.

These databases contain citations from different subsets of available publications and different time periods and thus the citation count from each is usually different. Some works are not in either database and no count is displayed.

Scopus includes citations from articles published in onwards, and Web of Science® generally from onwards. Export: EndNote Dublin Core BibTeX. Repository Staff Only: item control page. QUT Home Contact. Home Browse About. Description Purpose Commencing selected workouts with low muscle glycogen availability augments several markers of training adaptation compared with undertaking the same sessions with normal glycogen content.

Impact and interest: 37 citations in Scopus. Notify us of incorrect data How to use citation counts More information. More statistics Export: EndNote Dublin Core BibTeX Repository Staff Only: item control page.

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: Caffeine and power output

Caffeine increases motor output entropy and performance in 4 km cycling time trial | PLOS ONE

Smith JC, Dangelmaier BS, Hill DW Critical power is related to cycling time trial performance. Int J Sports Med 20 6 — Vanhatalo A, Doust JH, Burnley M Determination of critical power using a 3-min all-out cycling test.

Med Sci Sports Exerc 39 3 — Warren GL, Park ND, Maresca RD, McKibans KI, Millard-Stafford ML Effect of caffeine ingestion on muscular strength and endurance: a meta-analysis. Med Sci Sports Exerc 42 7 — Wiles JD, Coleman D, Tegerdine M, Swaine IL The effects of caffeine ingestion on performance time, speed and power during a laboratory-based 1 km cycling time-trial.

J Sports Sci 24 11 — Woolf K, Bidwell WK, Carlson AG The effect of caffeine as an ergogenic aid in anaerobic exercise. Int J Sport Nutr Exerc Metab 18 4 — Download references. The authors wish to thank the participants who contributed their time and effort to undertake this study and to Polypact International Co.

Department of Athletic Performance, National Taiwan Normal University, Taipei, Taiwan. Graduate Institute of Sports Training, University of Taipei, Taipei, Taiwan. Department of Physical Education, National Taiwan Normal University, Taipei, Taiwan. Center for General Education, National Sun Yat-sen University, No.

You can also search for this author in PubMed Google Scholar. Correspondence to Chia-Lun Lee. Reprints and permissions. Cheng, CF. et al. Caffeine ingestion improves power output decrement during 3-min all-out exercise. Eur J Appl Physiol , — Download citation.

Received : 13 January Accepted : 27 June Published : 02 July Issue Date : September Anyone you share the following link with will be able to read this content:. Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative. Abstract Purpose To investigate the effect of caffeine ingestion on the 3-min all-out test 3MT performance and plasma electrolytes in athletes. Results Significant differences in WEP CAF vs. Conclusions Caffeine ingestion did not change EP but improved WEP and the rate of decline in power output during short-term, severe exercise.

Access this article Log in via an institution. References Astorino TA, Roberson DW Efficacy of acute caffeine ingestion for short-term high-intensity exercise performance: a systematic review. Int J Sport Nutr Exerc Metab 21 1 —32 Article CAS PubMed Google Scholar Bazzucchi I, Felici F, Montini M, Figura F, Sacchetti M Caffeine improves neuromuscular function during maximal dynamic exercise.

J Appl Physiol 60 6 — CAS PubMed Google Scholar Bell DG, Jacobs I, Ellerington K Effect of caffeine and ephedrine ingestion on anaerobic exercise performance.

Med Sci Sports Exerc 33 8 — Article CAS PubMed Google Scholar Bergstrom HC, Housh TJ, Zuniga JM, Traylor DA, Camic CL, Lewis RW Jr, Schmidt RJ, Johnson GO The relationships among critical power determined from a 3-min all-out test, respiratory compensation point, gas exchange threshold, and ventilatory threshold.

Scand J Rehab Med —98 CAS Google Scholar Burnley M, Doust JH, Vanhatalo A A 3-min all-out test to determine peak oxygen uptake and the maximal steady state.

Med Sci Sports Exerc 38 11 — Article PubMed Google Scholar Cheng CF, Yang YS, Lin HM, Lee CL, Wang CY Determination of critical power in trained rowers using a three-minute all-out rowing test. Laurence Erlbaum Associates, New Jersey Google Scholar Collomp K, Ahmaidi S, Audran M, Chanal JL, Prefaut C Effects of caffeine ingestion on performance and anaerobic metabolism during the Wingate Test.

Int J Sports Med 12 5 — Article CAS PubMed Google Scholar Collomp K, Ahmaidi S, Chatard JC, Audran M, Prefaut C Benefits of caffeine ingestion on sprint performance in trained and untrained swimmers. Eur J Appl Physiol 64 4 — Article CAS Google Scholar Crowe MJ, Leicht AS, Spinks WL Physiological and cognitive responses to caffeine during repeated, high-intensity exercise.

Int J Sport Nutr Exerc Metab 16 5 — Article CAS PubMed Google Scholar Davis JK, Green JM Caffeine and anaerobic performance: ergogenic value and mechanisms of action. Eur J Appl Physiol 62 6 — Article CAS Google Scholar Doherty M The effects of caffeine on the maximal accumulated oxygen deficit and short-term running performance.

Int J Sport Nutr Exerc Metab 8 2 — Article CAS Google Scholar Doherty M, Smith PM Effects of caffeine ingestion on rating of perceived exertion during and after exercise: a meta-analysis. Scand J Med Sci Sports 15 2 —78 Article CAS PubMed Google Scholar Fitts RH Cellular mechanisms of muscle fatigue.

Physiol Rev 74 1 —94 CAS PubMed Google Scholar Forbes SC, Candow DG, Little JP, Magnus C, Chilibeck PD Effect of Red Bull energy drink on repeated Wingate cycle performance and bench-press muscle endurance. Int J Sport Nutr Exerc Metab 17 5 — Article CAS PubMed Google Scholar Fukuda DH, Smith AE, Kendall KL, Stout JR The possible combinatory effects of acute consumption of caffeine, creatine, and amino acids on the improvement of anaerobic running performance in humans.

Int J Sports Med 6 4 — Article CAS PubMed Google Scholar Ganio MS, Klau JF, Casa DJ, Armstrong LE, Maresh CM Effect of caffeine on sport-specific endurance performance: a systematic review. Int J Sport Nutr Exerc Metab 18 2 — Article CAS PubMed Google Scholar Gliottoni RC, Meyers JR, Arngrimsson SA, Broglio SP, Motl RW Effect of caffeine on quadriceps muscle pain during acute cycling exercise in low versus high caffeine consumers.

Int J Sport Nutr Exerc Metab 19 2 — Article CAS PubMed Google Scholar Goldstein ER, Ziegenfuss T, Kalman D, Kreider R, Campbell B, Wilborn C, Taylor L, Willoughby D, Stout J, Graves BS, Wildman R, Ivy JL, Spano M, Smith AE, Antonio J International society of sports nutrition position stand: caffeine and performance.

J Appl Physiol 78 3 — CAS PubMed Google Scholar Greer F, McLean C, Graham TE Caffeine, performance, and metabolism during repeated Wingate exercise tests.

J Appl Physiol 85 4 — CAS PubMed Google Scholar Hopkins W Estimating sample size for magnitude-based inferences. Int J Sport Nutr Exerc Metab 18 3 — Article CAS PubMed Google Scholar Johnson TM, Sexton PJ, Placek AM, Murray SR, Pettitt RW Reliability analysis of the 3-min all-out exercise test for cycle ergometry.

Med Sci Sports Exerc 37 12 — Article CAS PubMed Google Scholar Kalmar JM, Cafarelli E Effects of caffeine on neuromuscular function. J Appl Physiol 87 2 — CAS PubMed Google Scholar Kolbe T, Dennis SC, Selley E, Noakes TD, Lambert MI The relationship between critical power and running performance.

J Appl Physiol 1 — Article CAS PubMed Google Scholar Mohr M, Nielsen JJ, Bangsbo J Caffeine intake improves intense intermittent exercise performance and reduces muscle interstitial potassium accumulation. Ergonomics — Article Google Scholar Moritani T, Nagata A, deVries HA, Muro M Critical power as a measure of physical work capacity and anaerobic threshold.

Med Sci Sports Exerc 38 3 — Article CAS PubMed Google Scholar Naharudin MN, Yusof A Fatigue index and fatigue rate during an anaerobic performance under hypohydrations.

J Appl Physiol 91 4 — CAS PubMed Google Scholar Poole DC, Ward SA, Gardner GW, Whipp BJ Metabolic and respiratory profile of the upper limit for prolonged exercise in man. Ergonomics — Article CAS PubMed Google Scholar Santos Rde A, Kiss MA, Silva-Cavalcante MD, Correia-Oliveira CR, Bertuzzi R, Bishop DJ, Lima-Silva AE Caffeine alters anaerobic distribution and pacing during a m cycling time trial.

Int J Sport Health Sci —26 Article Google Scholar Simmonds MJ, Minahan CL, Sabapathy S Caffeine improves supramaximal cycling but not the rate of anaerobic energy release.

Int J Sports Med 20 6 — Article CAS PubMed Google Scholar Vanhatalo A, Doust JH, Burnley M Determination of critical power using a 3-min all-out cycling test. Do not confuse milligrams with grams when using caffeine supplements. Caffeine is a fairly safe supplement at the recommended doses.

It may cause minor side effects in some people and should be used with caution in individuals with heart disease, high blood pressure, GERD, and several other conditions. Caffeine is one of the most effective exercise supplements available.

Studies have shown that caffeine can benefit endurance performance, high intensity exercise, and power sports. However, it seems to benefit trained athletes the most.

Both caffeine anhydrous supplements and regular coffee provide performance benefits. Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available.

VIEW ALL HISTORY. Find out about the health risks of caffeine anhydrous, the powdered caffeine in supplements and energy drinks, and those of caffeine in general. Caffeine can have impressive health benefits, but high doses can also lead to unpleasant side effects.

Here are 9 side effects of too much caffeine. Caffeine can kick start your senses within 15 minutes. See exactly what caffeine does to your body with this interactive graphic.

Targeting heart rate zones as you exercise is one way to maximize the benefits you get from your workouts.

Learn about your different heart rate zones…. There are several causes of numbness in your toes and feet when you run, ranging from poor-fitting shoes to health conditions like diabetes. For people who run or do other aerobic exercises on a regular basis, starting up a low heart rate training program may be frustrating at first.

The average 5K time depends on a few factors, including age, sex, and fitness level. But, you can expect to finish a 5K in roughly 30 to 40 minutes. Thinking about using an AI tool like ChatGPT to help you get in shape? Here are the pros and cons health experts say you should consider. We're testing the Lululemon product for you and weighing in on whether the trend has past or if it's still worth the hype.

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How Well Do You Sleep? Health Conditions Discover Plan Connect. Get Motivated Cardio Strength Training Yoga Rest and Recover Holistic Fitness Exercise Library Fitness News Your Fitness Toolkit.

Nutrition Evidence Based How Caffeine Improves Exercise Performance. Medically reviewed by Kathy W. Warwick, R. Basics Endurance performance High intensity exercise Strength exercises Fat loss How to supplement Side effects Bottom line Caffeine is a powerful substance that can improve both your physical and mental performance.

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Caffeine and strength exercises. Caffeine and fat loss. How to supplement with caffeine. Privacy Preferences. Essential cookies. Marketing cookies. Personalization cookies. Analytics cookies. Reject all cookies Allow all cookies Save preferences. ISIC Home. Health conditions.

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How Caffeine Improves Exercise Performance Hawley and J. Many studies conducted among athletes competing in team and individual sports, report that caffeine may enhance performance in a variety of sport tasks. Prevalence of illness, poor mental health and sleep quality and low energy availability prior to the Summer Olympic Games Drew, Michael, Vlahovich, Nicole, Hughes, David, Appaneal, Renee, Burke, Louise, Lundy, Bronwen, Rogers, Margot, Toomey, Mary, Watts, David, Lovell, Gregory, Praet, Stephan F. Table 2 Results from the subgroup meta-analyses Full size table. Al-Fares MN, Alsunni AA, Majeed F, Badar A. None of the remaining subgroup analysis showed a significant effect of caffeine.
Caffeine increases motor output entropy and performance in a 4 km cycling time trial Different CAF dietary strategies are used to enhance performance Farina D, Arendt-Nielsen L, Merletti R, Graven-Nielsen T. Percept Mot Skills. Due to infrequent reporting of individual data it is difficult to determine the extent to which variation in responses may be occurring. Correction: Wilk et al. Dömötör, Z. Mice with whole-body disruption of AMPK-glycogen binding have increased adiposity, reduced fat oxidation and altered tissue glycogen dynamics.
Caffeine ingestion improves power output decrement during 3-min all-out exercise

These Bayes Factor indicated that the posterior probability favoring the alternative hypothesis were moderate and strong, respectively. According to Bayes Factor analyzes for average power output, there is a posterior probability of These Bayes Factor indicated that the posterior probability favoring the alternative hypothesis were strong and very strong, respectively.

The results from inferential and Bayesian statistics are presented in Table 3. The parameter V0 was significantly greater in the condition PP when compared to other conditions.

The V0 exhibited a decline along the TT-test. The condition CC was significantly lower than PP condition at the midway of the exercise protocol.

It was observed a significantly increase along the TT-test Fig. The V2 was significantly greater in the condition CC when compared to other conditions. Additionally, the V2 increased along the TT-test.

At the condition PC, the V2 exhibited a significantly increase from midway to the final of exercise protocol. At the final of exercise protocol, CC and PC exhibited greater V2 when compared to the condition PP Fig. According to Bayes Factor analyzes, there is a posterior probability of For V2, the Bayes Factor analyzes indicated a posterior probability The results from inferential and Bayesian statistics are presented in Table 4.

Since our study presented data from 1 procedures to ensure the control of experiments blood CAF quantification, HRV PRE suppl and POS exerc ; 2 performance in TT-test; 3 HRV along and after the TT-test, the discussion was structured to follow the exposed sequence.

In our study, volunteers performed the TT-test under the same nutritional conditions, since the h dietary records did not show significant differences between the PP, PC, and CC conditions.

Additionally, the presence of foods, substances, supplements, or medicines containing CAF was also not detected in the records, since blood analysis by HPLC confirmed no serum CAF concentration in athletes at the baseline for PC and CC conditions , and after the supplementation, when submitted to placebo condition i.

As expected, at the conditions PC and CC, blood CAF concentration increased 1 h after supplementation Table 1. It is important to highlight that the use of analytical methods, as HPLC, to detect CAF in blood samples before and after supplementation is fundamental control method to ensure and validate the supplementation effects 27 and, in our study, was critical to ensure that volunteers performed the tests exclusively under the effect of experimental supplementation of CAF i.

Other adopted procedure to ensure the control of experiments was the recordings of successive RR intervals before and after supplementation, and our results indicated no differences among the CAF i.

A recent study 28 investigated the influence of different caffeinated beverages energy drink, coffee, and cola on HRV parameters obtained through non-linear methods. From a 5-min recording at sitting position, the authors identified that energy drink and coffee beverages could influence the HRV complexity parameters: Largest Lyapunov exponent and correlation dimension , suggesting a greater variability of successive RR intervals, which have been associated to a better health status.

The use of non-linear methods to analyze the RR intervals variability has been reported as a more suitable tool to quantify complex phenomena such as control of cardiac function mediated by ANS 29 , Results from pharmacological blockage 29 and during tilt test 29 found that the V0 pattern reflects sympathetic modulation, the V2 pattern parasympathetic modulation, and the V1 pattern reflects sympathovagal balance.

These results also confirm that the probability of harmful effects from acute CAF supplementation is anecdotal, which was confirmed by Bayesian analysis carried out in our study. It is important to note that the behavior of successive RR intervals is different at rest and along a high-intensity physical test, then, the significant differences in HRV parameters observed during the TT-test should be discussed apart from data obtained at supine position.

We found a significant acute performance improvement with CAF supplementation, independently of supplementation strategy i. PP to strong CC vs. PP posterior probability favoring the alternative hypothesis Table 3. The ergogenic effect of CAF is widely demonstrated, especially in TT-tests 31 , 32 , 33 , as we used.

The present study also observed a better power output performance of athletes in the caffeine condition when compared to the placebo condition. Curiously, the behavior of power output along the TT-test was clearly different between CAF supplementation PC or CC and placebo Fig.

At CAF supplementation conditions the power output was higher since the beginning of TT-test, maintaining quasi-stable along all the exercise, while at placebo condition the power was increasing along the exercise.

The excitatory and alerting effects caused by CAF may explain the increased locomotor activity seen at the beginning of the test Mechanisms involving the effects of caffeine at the level of the central pattern generator of the lumbar spine network, enhancing the locomotor action, have been recently described 35 , facilitating limb activity through inhibition of A1 receptors and subsequent activation of dopamine receptors through an intracellular mechanism dependent on cAMP-dependent protein kinase.

This effect probably leads to a great ability to develop power output since the beginning of the exercise. Compared to tests with anaerobic predominance, as the Wingate test, the chosen TT-test spends a long time to be completed, making it infeasible to apply a maximal power output all time along the exercise.

It is expected that experienced cyclists learn to control the intensity to complete the TT-test, then it is interesting the divergent behavior between supplemented conditions and placebo, since at placebo conditions volunteers adjusted the power output along the exercise, while at CAF supplementation they maintained the power output along all TT-test, being higher than placebo at the beginning of TT-test.

In general, well-designed caffeine supplementation strategies can contribute to the improvement of countermovement jump CMJ height, average power, peak power, endurance muscle, and strength muscle Findings 37 support the hypothesis that the ergogenic effect of CAF would act in a dose-dependent manner.

Furthermore, they suggest that habitual consumption of products containing CAF would alter the CAF supplementation effect.

Durkalec-Michalski et al. Thus, they suggested that athletes who habitually consume caffeine-containing products would need higher doses to promote specific performance improvement. The ergogenic effects of caffeine depend on several mechanisms that can vary, such as time course, dose, and magnitude of dependence.

Regular caffeine consumption positively induces the production of the Cytochrome P CYP1A2 enzyme group, increasing the rate of metabolism in regular users 5. Therefore, different consumption strategies added to acute intake doses pre-test can produce distinct ergogenic effects.

For example, Beaumont et al. This strategy impacts the ability to perform total work on the cycle ergometer, generating tolerance effects on endurance performance. Furthermore, constant caffeine use also affected cycle ergometer sprint performance.

Lara et al. They found that this strategy chronically caused a reduction in the magnitude of ergogenicity in the ventilatory response.

However, it significantly increased peak power during a maximal incremental test during the first 15 days of ingestion. They also found an improvement in VO 2 max in the first four days when compared to placebo treatment.

Daily caffeine intake before exercise also produced a higher peak power for approximately 18 days after ingestion. After that period, the performance increases were not statistically different from placebo. These results suggest the existence of progressive tolerance to the performance benefits of caffeine, as the ergogenic magnitude of caffeine was verified in the first days of ingestion for both endurance and muscle power exercises.

Thus, the time course of habituation is poorly understood and can be mainly affected by routine caffeine consumption. The impact of habituation probably can be modified by acute intake substantially greater than usual.

Concerns about caffeine consumption on cardiovascular activity during intense exercise are commonly related to dose, being reported that high-dose of caffeine intake can cause tachycardia, palpitations, and a rapid rise in blood pressure However, moderate caffeine intake does not adversely affect cardiovascular health 39 , despite moderate CAF consumption could affect contractility, myocardial conduction, vascular tone, and the sympathoadrenal system In this setting, the results of this study reinforce the possibility of increasing parasympathetic modulation after caffeine ingestion and add important information suggesting that the relationship between caffeine dosage and parasympathetic reactivity is not linear.

Sarshin et al. These data present robust evidence of an interesting clinical effect of CAF, diverging from the mainstream of harmful effect of CAF supplementation on cardiovascular health. It is worthwhile to emphasize that 41 did not analyzed the RR interval variability along the exercise, leaving a lack of information about the safety of caffeine during intense exercise.

Our data obtained along the TT-test indicated a progressive increase of the parameter V2, achieving higher values at CAF supplementation PC and CC , when compared to placebo. These find suggest a progressive increase of an indicator of parasympathetic activity The pattern variation of successive RR intervals, evaluated by symbolic analysis along the TT-test revealed that the sympathetic modulation V0 had similar behavior between the conditions PP, CP, and CC at the beginning and midway of the exercise, being more pronounced at the beginning of the test, as expected, owing to the high sympathetic drive at the beginning of exercises.

The V0 exhibited a decline along with the exercise, which could be related to expected cardiovascular adjusts along the submaximal long exercise. At the final of TT-test, we found an interesting behavior with smaller V0, a marker of sympathetic modulation, at CAF conditions PC and CC when compared to placebo.

The parameter V1 pattern reflecting sympathovagal balance exhibited an increase along the exercise, with similar behavior among the conditions. The parameter V2 pattern reflecting parasympathetic modulation increased along the TT-test similarly among supplementation conditions PP, PC, and CC at the beginning and midway of the exercise.

However, at the final, a prominent parasympathetic modulation was observed in the CAF conditions PC and CC compared to the placebo. These results could reflect a protective effect of CAF during the used TT-test since the sympathetic drive was not the greater in CAF conditions at the beginning of the activity, despite a higher power output at this moment.

Autonomic control during physical exercise under CAF conditions can be modified; the baroreflex is attenuated at the brainstem level due to activation of the metaboreflex. Increased metabolic accumulation i. As a consequence, stimulation of non-myelinated afferent fibers III and IV leads to sympathetic activity, inducing a more accentuated parasympathetic response due to the maintenance of output power for a longer time during exercise Similar responses were observed by Bunsawat et al.

The authors 42 observed a parasympathetic response with the ingestion of mg of caffeine capsules compared to the placebo condition, resulting in greater exercise performance.

Divergently from CAF conditions PC and CC , the placebo condition demanded more power output to complete the exercise at an expected time i. In line with this hypothesis, a parasympathetic withdrawal will be expected at the placebo condition, as we found. This suggests that the rapid onset of the sympathetic response in the final phase i.

They suggested that effective cardioprotection strategies should increase cardiac parasympathetic activity, thus conferring plausible efficiency in reducing myocardial damage and decreasing myocardial morbidity and mortality Notwithstanding, it is important to note that the posterior probability of greater V2 and smaller V0 along TT-test with CAF supplementation were moderate to very-strong, as found with Bayesian inference Table 4.

Clark et al. However, three methodological aspects need to be emphasized when comparing the results from this study 45 and ours. They used 1 a low dose of CAF an energy drink formula containing mg of caffeine ; 2 a graded exercise test to exhaustion; 3 a linear method to obtain estimations of heart autonomic modulation.

A significant parasympathetic withdrawal is expected in exercise designed to increase the intensity in a predetermined manner until failure, and the lower CAF dose could be not sufficient to sustain the parasympathetic modulation along the exercise.

Our study used an exercise mimetizing a competition, where the athlete could choose the intensity, but be aware of the aim of the exercise i. The last relevant difference between 45 and our study was the chosen method to analyze the variability of successive RR intervals, and nonlinear methods, as we used, is reported to be more suitable to quantify complex phenomena such as control of cardiac function mediated by ANS 46 , 47 , Despite the great effort to control the variables involved in the study, some limitations should be considered.

One of the limitations of our findings is associated with the use of a cycle ergometer in the laboratory. Thus, the findings of the present study should be confirmed in additional research protocols, which use field tests i.

Other limitations of the present study are related to the analysis of the plasma catecholamine concentrations and the sympathetic nerve activity; however, we used HRV, a simple non-invasive method and one of the most promising quantitative markers of autonomic heart rate balance The urine content of caffeine metabolites paraxanthine, theobromine, and theophylline was also not analyzed in the present study, which could indirectly reflect the pharmacokinetics of CAF.

It has been shown that the increase in the concentration of paraxanthine one of the metabolites of CAF has a different relationship with plasma levels of CAF after the min period of CAF ingestion time used in the present study The increase in paraxanthine occurs at a slower rate than the CAF in plasma during this period 60 min , making its detection in urine even more difficult Finally, we do not control Cytochrome P CYP1A2 polymorphisms.

These variations in genes encoding CYP1A2 proteins can impact caffeine metabolism and potentiate dopaminergic neurotransmission.

However, as this condition is uncommon, conducting a study with this genetic outcome requires a robust number of participants As a novelty from our study we highlight the use of a 16 km TT-test, a long task that mimetize cycling competitions tasks, instead of predominantly anaerobic tests, which have been used in previous studies, investigating the cardiovascular effects of CAF supplementation.

The use of symbolic analysis to estimate sympathovagal modulation, and the Bayesian inference as a statistical approach, also represent novelty, since previous studies in the field of our study did not include these promising mathematical approaches.

It is noteworthy that the cardioprotective effect of caffeine was observed in healthy volunteers, and our findings should not be transmitted to patients at high cardiovascular risk or cardiovascular disease. Other studies must be carried out to assess the effects of different doses of CAF, and establish the most accurate dosage that enhances the results, favors cardioprotection, and minimizes risks.

Assuming repeated measures, within factors three interventions. The inclusion criteria were: all had at least 4 years of experience, participated in at least 20 competitions in and , have no history of cardiorespiratory, gastrointestinal, and musculoskeletal disorders in the last 3 months.

A simple questionnaire evaluated the training volume of all participants to warrant a homogenous sample for the study.

In addition, a validated caffeine consumption questionnaire was administered to the participants, showing that all participants were moderate to high caffeine consumers The research protocol 2.

A randomized, double-blind, crossover, placebo-controlled design was used in this study. On the first visit to the laboratory, participants underwent dietary assessment and cycling test to exhaustion.

On the second visit, cyclists became familiar with the time trial test. So they received four visits from the researchers at home, one per day, for delivery and verification of capsule consumption according to randomization.

The other day they consumed the capsule acutely 60 min before the 16 km time trial test. The study preconized a seven-day washout between the different intervention strategies 19 , 20 , 21 , We tested the following strategies: Placebo—Placebo PP , participants received Placebo 4-day supplementation , and Placebo acute ingestion, 60 min before simulated cycling TT-test completed.

Placebo capsules were mg of magnesium silicate single daily dose. Placebo—Caffeine PC , participants received Placebo 4-day supplementation , and Caffeine acute ingestion, 60 min before simulated cycling TT-test completed.

Caffeine—Caffeine CC , participants received Caffeine 4-day supplementation , and Caffeine acute ingestion, 60 min before simulated cycling TT-test completed. At the first visit to the laboratory, the researchers verified the routine energy and caffeine intake of food, VO 2 max, and workload capacity in the graded test until exhaustion in the cycle ergometer.

The athletes were instructed to withdraw all their caffeine consumption i. On the test day, cyclists arrived fasting in the laboratory, and soon an intravenous cannula 20G Jelco; B.

Braun Medical Inc. Cyclists did not exercise 24 h before the experimental trials in the laboratory. The athletes were instructed to continue the routine of daily training. The experimental trials were performed at the same time of day a.

com Supplementary File -Disposition of study participants. To determine the VO 2 max, participants performed a graded exercise test to exhaustion on the cycle ergometer Cefise, São Paulo, Brazil.

Heart rate was monitored continuously Polar Electro Oy, Kempele, Finland. The pulmonary gas exchange was determined breath by breath for carbon dioxide, oxygen concentrations, and minute ventilation using a VO gas analysis system MedGraphics, St.

Paul, MN, USA. The equipment was automatically calibrated according to the manufacturer's specifications before each test. The present study determined and validated the VO 2 max following these criteria: increase in VO 2 less than 2.

Because the participants are used to consuming average amounts of caffeine daily, around In the presence of a researcher, all athletes were instructed to take a single capsule daily at the same time a. during the 4-day supplementation.

In acute ingestion, the capsule was administered with mL of water before simulated cycling TT-test completed. Supplements for each participant were prepared and separated by a non-affiliated researcher to ensure double-blinding.

With this information, we would know the percentage of belief of caffeine consumption. A high frequency of this belief could influence the study results as described by other authors Cyclists were instructed to maintain their dietary and hydration patterns. A h dietary record was completed by each athlete on the first visit and, before the first test, it was photocopied and returned to the athletes so that the same diet could be repeated for subsequent trials.

The energy intake, carbohydrates, total proteins, and total lipids was determined. The TACO database was used to quantify macronutrient intake and the Dietpro 5i software version 5.

To assess the dietary frequency and the amount of caffeine, a validated questionnaire was applied by trained nutritionists.

The questionnaire consists of a list of dietary sources of CAF coffee, tea, cocoa, chocolate, soft drinks, medicines, and dietary supplements and the time of consumption. Household measures were used to assess the amount of food consumed according to the following frequency of consumption Types of foods, dietary supplements, and medications that contained caffeine were identified.

The CAF content was obtained from the U. Successive RR intervals were acquired for 5 min while supine REST and along the TT-test. Beat-to-beat intervals were recorded by a validated heart rate monitor Polar RS, Polar Electro Oy, Kempele, Finland for HRV analysis The sampling frequency was set at Hz, the smoothness prior method with alpha set at was used for detrended the R-R intervals series.

They were studied 48 h far away from the last bout of physical exercise to avoid the short-term autonomic and cardiovascular confounding after-effects induced by recent training sessions. Recordings at supine position HRV-SP were performed three times, before the ingestion of the capsule PRE suppl , 60 min after supplementation PRE exerc , and 10 min after the TT-test POST.

Recording of the HRV during the TT-test HRV-TT was done during the entire time of the exercise execution. The nonlinear dynamics of successive RR intervals were assessed by symbolic analysis 29 during the TT-test.

The R-R dynamics were classified into three pattern families: I patterns with no variation V0; all three symbols were equal ; II patterns with one variation V1; two consequent symbols were equal, and the remaining symbol was different ; and III patterns with two unlike or like variations V2; all of the symbols were different from the previous ones.

The percentage of the patterns V0 was calculated as sympathetic modulation predominance, V1 reflects sympathetic and parasympathetic modulation, and the V2 calculated as a parasympathetic modulation as suggested by Santos et al.

The data i. For the recordings from supine position, the 5-min successive RR intervals were selected for analysis, while for TT-test, the visual inspection was carried out to find and select a segment of successive RR intervals where the stationarity of the time series was acceptable at three moments: beginning, midway and final of each TT-test session.

All RR interval variability analyses were carried out by the same researcher which was blind for the applied treatment in each data set. The measurement of blood levels of caffeine was performed at baseline and 60 min after intake of capsules.

Serum was obtained by centrifugation at 2. The caffeine blood levels were determined using a HPLC method previously described The HPLC analyses were carried out using a Shimadzu chromatograph Shimadzu Corp.

Participants did not receive any performance feedback during the tests. The only information that the participants received was the distance reached: 2 km, 4 km, 6 km, 8 km, 10 km, 12 km, 14 km, and 16 km. The analyses of the power outputs were measured in 3 equals intervals Beginning, Midway and Final of the completed TT-test time curve.

The dynamics of data acquisition in the laboratory can be seen in Fig. Dynamics of data acquisition. Placebo—Placebo PP , Placebo—Caffeine PC and Caffeine—Caffeine CC conditions were tested in 16 km time Trial 16 km TT performance and HRV analysis were done pre supplementation HRV-SP PRE suppl , post supplementation HRV-SP POST suppl during 16 km TT HRV-TT and post 16 km TT HRV-SP Post.

When data showed normal distribution the variables were analyzed by mixed ANOVA with repeated measures. The Mauchly sphericity test was performed for all tested variables, and the Greenhouse—Geisser correction was used in cases where the sphericity assumption was violated.

Tukey's post hoc test was used for means multiple comparisons. Assuming this hypothesis is right, one may also expect that caffeine may further attenuate the fatigue-induced reduction in MOEn as the trial progresses, thereby likely improving power output and performance [ 25 ].

Therefore, the present study aimed to characterize MOEn in a TT 4km and verify if caffeine ingestion increases power output complexity and performance in this trial. We hypothesized that caffeine would attenuate a fatigue-induced reduction in power output complexity, improving power output and performance during TT 4km.

Nine endurance-trained male cyclists kg min -1 , having a minimum 3 years training experience competing at regional competitions, classified as performance level 3 [ 26 ] and experienced in cycling time trials, volunteered to participate in this study.

They were non-smokers and had no neuromuscular or cardiopulmonary disorder that could affect the study outcomes. The experimental procedures were previously approved by the Research Ethics Committee of the University of São Paulo After a preliminary visit to obtain anthropometric measures and assess the VO 2MAX through a maximal incremental cycling exercise performed with a 80 rpm pedal cadence 25 W·min -1 increases until exhaustion , cyclists attended to 3 sessions in a counterbalanced order; 1 a baseline 4 km cycling time trial TT 4km ; 2 a TT 4km after caffeine ingestion; 3 a TT 4km after placebo ingestion.

All visits were interspersed by a ~7 days interval. The cyclists were encouraged to maintain the training schedule intensity and volume throughout the study period and avoid vigorous exercise, alcohol, and stimulant or caffeine beverages for the last 24 h before the sessions.

Briefly, we chose a TT 4km as a strenuous whole-body self-paced exercise and assumed that endurance-trained cyclists complete this trial having a mean power output higher than W [ 15 , 16 ], therefore potentiating a likely reduction in MOEn [ 18 ].

In contrast, caffeine ingestion may increase MOEn and TT 4km performance. Caffeine and placebo capsules 6 mg. kg -1 of body mass were ingested ~ 60 min before the TT 4km commencement. Caffeine and sucrose-based i. placebo substances were formulated in opaque capsules of equal size, color and taste to prevent that participants rightly guessed the treatment.

Importantly, instead of a double-blind, randomized placebo-controlled clinical trial, we used a placebo-deceived design, as some have argued that the use of double-blind designs is a possible source of bias in clinical trials [ 29 , 30 ].

To ensure that eventual differences between caffeine and placebo were solely due to caffeine pharmacological effects, cyclists were led to believe they ingested caffeine in both sessions and the study was investigating the reproducibility of caffeine effects on TT 4km performance.

They were informed about the presence of a placebo condition at the study completion, as reported elsewhere [ 31 ]. Informal and anecdotal communication revealed that participants were blinded about the presence of a true placebo pill.

All cyclists performed the TT 4km on the same road bike Giant®, Thousand Oaks, CA, USA attached to a cycle-simulator calibrated before every test Racer Mate®, Computrainer, Seattle, WA, EUA , individually fitted with crank, pedals and saddle. This equipment provided power output measures W at a 2Hz sampling rate.

The validity and reliability of this system have been previously reported [ 32 , 33 ]. Cyclists performed a standard 7 min warm-up, consisting of a 5 min self-paced gear and cadence freely adjusted and a 2 min controlled-pace cycling fixed gear at W and 80 rpm pedal cadence. When they were still cycling at the end of the controlled-pace warmup, they immediately started the TT 4km.

The cyclists were oriented to rate their perceived exertion RPE at each 0. A researcher unaware of the substance ingested encouraged the cyclists to complete the distance as fast as possible, while distance feedback was available to cyclists to pace themselves.

The entropy could be interpreted as a non-linear analysis that provides a measure of the complexity of a system [ 35 ]. Based on the information theory, entropy is a measure that reflects the level of uncertainty of a dataset or time series.

Entropy can be obtained as the probability p k of each possible event multiplied by log of the inverse probability of each event [ 36 ] as described in Eq 1. However, the prior knowledge of the probability p k for the occurrence of all events is impossible in stochastic processes, therefore, adequate methodologies such as the sample entropy SampEn have been suggested [ 37 ].

The SampEn Eq 2 fits the approximate entropy [ 38 ] to generate less time series length-dependence and self-matching-reduced bias Eq 2. Where m is the length of sequences to be compared, r is the tolerance for accepting matches and N is the length of the time series.

In the SampEn algorithm, r is multiplied by the standard deviation SD of N , providing a matching threshold and allowing comparisons among sequences of m points. Readers are referred to a seminal work by Richman et al. In this study MOEn was estimated applying SampEn algorithm in the mechanical power output signal obtained during TT 4km.

A custom code Matlab v. This improved power output in caffeine was reflected in ~1. Additionally, cyclists presented comparable mean RPE during the TT 4km in both supplementations with caffeine 16 ± 0.

and placebo 16 ± 0. Mechanical power output panel A and motor output entropy panel B in placebo and caffeine trials. Mechanical power output relative to a percentage of the TT 4km distance.

Fig 3 depicts MOEn responses during the cycling trial, and Table 1 shows individual power output and MOEn responses over the TT 4km in both supplementations. Motor output entropy was expressed relative to a percentage of the TT 4km distance. Table 2 shows all correlation coefficients between MOEn and power output.

This study aimed to characterize the MOEn during a TT 4km and investigate if caffeine could change the MOEn-fatigue interplay during this strenuous, whole-body short cycling exercise. Our results showed a progressive reduction in motor output complexity as the TT 4km progressed, however caffeine increased TT 4km performance through an altered MOEn-fatigue interplay.

These results may support the notion that caffeine increases power output responses and attenuates the fatigue-induced reduction in MOEn during TT 4km. This is the first study characterizing the MOEn during a natural exercise mode with high ecological validity such as a strenuous, whole-body short cycling time trial.

Briefly, MOEn responses could involve changes in neuromuscular complexity such as in CNS areas such as cortical, subcortical and spinal areas, as well as in motor neuron conduction to skeletal muscles. However, despite the increasing exercise-induced perturbation, neuromuscular fatigue was likely low over this half of the trial and probably allowed an increased MOEn when regulating the motor output during this part [ 40 ].

One may argue that neuromuscular fatigue is low during this initial part of the trial, thus likely allowing an adequate response of the neuromuscular system to the exercise-imposed perturbation through an increased motor unit firing variability. In contrast, such a correlation between power output and MOEn was not observed in placebo TT 4km during these parts.

This is a part of the cycling trial usually characterized by a sharp increase in power output i. end spurt , so that one may hypothesize that the loss of MOEn during this latter part of the TT 4km was possibly related to a higher motor unit firing frequency, as neuromuscular fatigue is higher in the second half of a cycling trial [ 40 ].

A short cycling time trial having an end spurt may be a challenging scenario for the neuromuscular system, as this may represent fewer chances to vary muscle recruitment during pedaling mainly at the final stages of the trial [ 18 ], thereby reducing the mechanical power output variability i.

power output bandwidth and MOEn. This hypothesis is based on a previous study that reported a different neuromuscular strategy as indicated by EMG analysis when contrasting fixed-load cycling at W vs W [ 18 ]. The authors of that study concluded that the lower EMG entropy observed during higher cycling power output was likely due to a higher synchronism of motor units firing.

The present study hypothesized that caffeine may increase MOEn by increasing motoneuronal gain and changing the input-output relationship in the motor pathway, thereby resulting in a greater variability in motor output.

Although caffeine effects on skeletal muscles cannot be ruled out [ 41 ], the most convincing caffeine mechanism involves its action on neuronal A 1 adenosine receptors, as improvements in exercise performance after caffeine ingestion have been associated with increases in spinal and supraspinal excitability [ 42 , 43 ].

Analysis of movement variability have been used in different research fields [ 1 , 2 , 44 ], so that such analysis have been recently incorporated in neuromuscular fatigue studies [ 5 , 6 ].

In an exercise performance scenario, nonlinear measures such as MOEn may be a useful mean to estimate exercise-induced neuromuscular fatigue and its repercussion on motor control and performance responses [ 5 ]. Therefore, such a nonlinear measure could be helpful to improve the understanding of exercise performance and fatigue in different fields of sports sciences.

The increased motoneuronal gain suggestion should be interpreted with caution, as no specific measures were performed to indicate motoneuronal gain. Insights to a motoneuronal gain mechanism could be obtained with advanced EMG techniques, such as the motor unit decomposition algorithms from electrode matrices-derived signal [ 45 ].

However, this technique is still restricted to low-intensity isometric contractions so that the dynamic whole-body exercise used in the present study limited the use of these measures to provide motoneuronal gain mechanisms insights after caffeine ingestion. Future studies comparing recruitment and de-recruitment frequencies of pairs of motor units could shed-light on caffeine effects on motoneuronal gain during voluntary contractions [ 46 ].

The present study is descriptive rather than mechanistic, and its design and methods may not elucidate if losses in power output entropy during cycling time trial were due to central or peripheral fatigue factors. In this sense, the power output was sampled at a 2 Hz frequency, a sampling rate that may not detect all variability in power output data, given the possible aliasing effect resulted from sampling the data in different pedal positions at each revolution.

Another limitation was the absence of EMG responses, a measure that could have assessed the neuromuscular system and power output entropy, simultaneously.

However, considering that habitual caffeine consumption may change physiological responses to caffeine supplementation such as heart rate and ventilation, future studies may want to investigate potential habitual caffeine consumption effects on MOEn and EMG during cycling time trial.

However, caffeine ingestion improved TT 4km performance and MOEn. These results reinforce a likely fatigue-induced loss of complexity hypothesis. Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Article Authors Metrics Comments Media Coverage Reader Comments Figures.

Correction 22 Jan Viana BF, Trajano GS, Ugrinowitsch C, Pires FO Correction: Caffeine increases motor output entropy and performance in 4 km cycling time trial. Abstract Caffeine improves cycling time trial performance through enhanced motor output and muscle recruitment. Introduction According to the dynamic system theory, the variability presented by a given physiological system, a concept that is known as complexity, may reflect its flexibility to face natural perturbations [ 1 , 2 ].

Methods Participants and experimental design Nine endurance-trained male cyclists Caffeine and placebo ingestion Caffeine and placebo capsules 6 mg. Instruments, measures, and analysis All cyclists performed the TT 4km on the same road bike Giant®, Thousand Oaks, CA, USA attached to a cycle-simulator calibrated before every test Racer Mate®, Computrainer, Seattle, WA, EUA , individually fitted with crank, pedals and saddle.

Entropy calculation The entropy could be interpreted as a non-linear analysis that provides a measure of the complexity of a system [ 35 ]. Int J Sports Med 6 4 — Ganio MS, Klau JF, Casa DJ, Armstrong LE, Maresh CM Effect of caffeine on sport-specific endurance performance: a systematic review.

J Strength Cond Res 23 1 — Gliottoni RC, Motl RW Effect of caffeine on leg-muscle pain during intense cycling exercise: possible role of anxiety sensitivity.

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J Appl Physiol 78 3 — Greer F, McLean C, Graham TE Caffeine, performance, and metabolism during repeated Wingate exercise tests. J Appl Physiol 85 4 — Hopkins W Estimating sample size for magnitude-based inferences. Sportscience — Int J Sport Nutr Exerc Metab 18 3 — Johnson TM, Sexton PJ, Placek AM, Murray SR, Pettitt RW Reliability analysis of the 3-min all-out exercise test for cycle ergometry.

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J Appl Physiol 5 — Monod H, Scherrer J The work capacity of a synergic muscular group. Ergonomics — Moritani T, Nagata A, deVries HA, Muro M Critical power as a measure of physical work capacity and anaerobic threshold.

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Santos Rde A, Kiss MA, Silva-Cavalcante MD, Correia-Oliveira CR, Bertuzzi R, Bishop DJ, Lima-Silva AE Caffeine alters anaerobic distribution and pacing during a m cycling time trial. PLoS One 8 9 :e Article CAS PubMed Central Google Scholar.

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Int J Sports Med 20 6 — Vanhatalo A, Doust JH, Burnley M Determination of critical power using a 3-min all-out cycling test. Med Sci Sports Exerc 39 3 — Warren GL, Park ND, Maresca RD, McKibans KI, Millard-Stafford ML Effect of caffeine ingestion on muscular strength and endurance: a meta-analysis.

Med Sci Sports Exerc 42 7 — Wiles JD, Coleman D, Tegerdine M, Swaine IL The effects of caffeine ingestion on performance time, speed and power during a laboratory-based 1 km cycling time-trial.

J Sports Sci 24 11 — Woolf K, Bidwell WK, Carlson AG The effect of caffeine as an ergogenic aid in anaerobic exercise.

Int J Sport Nutr Exerc Metab 18 4 — Download references. The authors wish to thank the participants who contributed their time and effort to undertake this study and to Polypact International Co.

Department of Athletic Performance, National Taiwan Normal University, Taipei, Taiwan. Graduate Institute of Sports Training, University of Taipei, Taipei, Taiwan.

Purpose: Commencing selected workouts with low muscle glycogen availability augments several markers of training adaptation compared with outptu the same sessions with ;ower glycogen content. We Caffeine and power output Chitosan for joint health a low Caffeine and power output of caffeine could partially rescue the reduction powre maximal Caffeine and power output power output observed when powerr commenced high-intensity interval training with low LOW compared with normal NORM glycogen availability. Muscle glycogen content was manipulated via exercise—diet interventions so that two experimental trials were commenced with LOW and two with NORM muscle glycogen availability. Sixty minutes before an experimental trial, subjects ingested a capsule containing anhydrous caffeine CAFF, 3 mg-1·kg-1 body mass or placebo PLBO. Instantaneous power output was measured throughout high-intensity interval training 8 × 5-min bouts at maximum self-selected intensity with 1-min recovery. Results: There were significant main effects for both preexercise glycogen content and caffeine ingestion on power output.

Video

What Caffeine Does To Your Brain

Caffeine and power output -

Twenty studies 21 trials used a pre-load exercise protocol which requires exercise of a fixed duration being completed immediately before the time trial portion [ 39 , 44 , 45 , 50 , 51 , 52 , 58 , 59 , 63 , 64 , 67 , 68 , 71 , 72 , 74 , 75 , 77 , 78 , 79 ]. The mean total exercise duration was Overall, caffeine time-trials were faster compared to placebo by 2.

Similarly, power output in caffeine trials were greater compared to placebo trials by 2. Only two trials [ 37 , 38 ] showed a slower time trial time following caffeine ingestion compared to placebo. However, 4 trials 3 studies [ 41 , 42 , 56 ] had lower MPO during caffeine trials compared to placebo.

Mean percent improvement in time trial performance time following caffeine ingestion compared to placebo trial. PLA placebo trials; CAFF caffeine trials.

SMD standard mean difference; CI confidence interval. Mean percent improvement in time trial performance MPO following caffeine ingestion compared to placebo trial. The mean PEDro score across all studies was 9. According to the funnel plots Figs. Funnel plot of standard mean difference against standard error for time-trial completion time.

se SMD standard error of the mean difference; SMD standard mean difference; CI confidence interval. Funnel plot of standard mean difference against standard error for MPO. The purpose of this systematic review and meta-analysis was to critically evaluate the effect of acute caffeine ingestion on endurance time-trial performance.

These findings are similar to Ganio et al. However, an earlier meta-analysis by Doherty et al. They found an increase in endurance performance during cycling tests of However, the analysis by Doherty et al.

Meta-regression analysis showed no association between caffeine dose, VO 2 , exercise duration, and exercise mode and mean performance improvement between caffeine and placebo. As seen in Figs. A number of factors can influence individual responses and metabolism of caffeine including smoking [ 82 ], age [ 83 ], and gender [ 84 ].

Smoking increases enzyme activity which causes caffeine to be metabolised faster [ 82 ]. Likewise, the older an individual is, the slower the rate of caffeine metabolism in the body [ 83 ]. Gender can also play a large role on the rate of caffeine metabolism such that women metabolise caffeine at different rates which is dependent on the stage of the menstrual cycle, as well as the use of oral-contraceptives, which can prolong the half-life of caffeine in the body [ 84 ].

Thus, when conducting caffeine supplementation studies, factors such as sex, age and smoking status should be taken into consideration when designing the study and comparisons that will be made.

Genetics has also been shown to contribute to the variability in responses to caffeine ingestion [ 85 ]. Specifically the CYP1A2 and ADORA2A genes have been identified as large contributors to caffeine metabolism and caffeine sensitivity, respectively [ 85 ].

Caffeine typically has a half-life of 3—5 h in healthy adults, therefore those with a faster metabolism may not experience the ergogenic effects of caffeine for the duration of an event if it is metabolised prior to the end of the exercise in long duration activities such as, marathons, triathlons and ultra-endurance events.

Only one study included in the present review conducted genetic analysis pertaining to caffeine metabolism [ 57 ]. Womack et al. However, more research is needed to determine the effects of CYP1A2 genotype on the ergogenicity of caffeine as well as controlling for confounding variables such as other genetic factors ADORA2A and epigenetic factors such as, age, smoking, gender and ethnicity.

The ADORA2A gene encodes for certain adenosine receptors found predominantly in the brain. As caffeine is an adenosine receptor antagonist it is likely that variations in the ADORA2A gene will affect the actions of caffeine on the adenosine receptor.

Little research exists on ADORA2A and the effects it could have on caffeine and exercise. Loy et al. As seen in Fig. However, each group only consisted of 6 participants which limits the impact of the finding, but still suggests that ADORA2A genotype may have a large effect on the effectiveness of caffeine supplementation for endurance exercise.

Significantly more work needs to be conducted to determine the role genetics could potentially play on the ergogenicity of caffeine as well as other popular supplements in order to fully maximise its effects. The fastest official half-marathon time is 58 min 23 s. With the average performance increase found across the studies presented here being 2.

Therefore, whether or not an athlete consumes caffeine prior or during an endurance event may have a large impact on the overall results. However, many of the studies included in this review were conducted on recreationally trained athletes and not of the elite level, thus it is possible that the proposed effect of caffeine is not generalisable to elite level athletes.

Athletes may also want to familiarise themselves with caffeine consumption during training and find the consumption protocol which provides the best possible effects for their own individual needs.

To date, not enough research exists for individualised recommendations, thus it is up to the athlete and training staff to determine the best timing, dosage and method to consume caffeine for the athletes training and competition needs.

The present meta-analysis does not include time-to-exhaustion studies as they have greater variability and less reliability than time-trial studies [ 7 ]. Furthermore, cycling is the main exercise modality used in these studies, most likely due to the ease of measurement when using a cycle ergometer.

However, results may vary when other exercise modalities are employed in the testing protocols, but a larger variety of exercise modalities would provide stronger evidence for the ergogenic effects of caffeine on endurance performance in multiple sports. Additionally, many of the participants used in the included studies were recreationally trained athletes, and further studies comparing the differences in the ergogenicity of caffeine between recreational and elite athletes is warranted.

As a result, there are many studies that have begun investigating the effects of caffeine in combination with other popular supplements, however, more work is still required in this area. The results of the present meta-analysis indicate caffeine has a small positive effect 2. However, large inter-individual responses to caffeine ingestion still exist and reasons for this variance between individuals should be further explored and taken into consideration when prescribing caffeine supplementation for athletes.

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MOEn mirrored power output responses as an inverted U-shape MOEn during the time trial. Caffeine ingestion improved TT 4km performance and motor output responses likely due to a greater power output entropy. Citation: Ferreira Viana B, Trajano GS, Ugrinowitsch C, Oliveira Pires F Caffeine increases motor output entropy and performance in 4 km cycling time trial.

PLoS ONE 15 8 : e Editor: Chris Harnish, Mary Baldwin University Murphy Deming College of Health Sciences, UNITED STATES. Received: March 25, ; Accepted: July 8, ; Published: August 13, Copyright: © Ferreira Viana et al.

This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper and supporting information files. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist. According to the dynamic system theory, the variability presented by a given physiological system, a concept that is known as complexity, may reflect its flexibility to face natural perturbations [ 1 , 2 ]. For example, the neuromuscular system is characterized by regular fluctuations in electrophysiological responses i.

complexity which enable the central nervous system CNS to adapt to environment-induced perturbations [ 3 ]. Assuming that every single body motion is a dynamic acceleration-deceleration interplay [ 4 ], the level of complexity in motor output responses may indicate the CNS ability to face a physical task-induced perturbation.

Studies have reported an association between motor output complexity and fatigue, as a reduced knee extensor torque entropy has been observed as a fatiguing single-joint isometric exercise progresses [ 5 , 6 ].

Studies investigating the MOEn-fatigue relationship have used highly controlled isometric muscle tasks as an exercise mode [ 5 , 6 ].

Despite providing a well-controlled intensity and power output response, this exercise mode has a low ecological validity as it reflects an unnatural form of exercise. Consequently, isometric muscle task-derived results cannot provide enough to understand the MOEn in more usual forms of exercise.

For example, exercises such as a cycling time trial may be insightful to understand the MOEn-fatigue relationship in strenuous whole-body self-paced exercises, as this exercise mode requires a more complex, moment-to-moment regulation when regulating pacing and exercise performance [ 8 — 15 ].

For example, power output fluctuations during a cycling time trial may indicate the CNS ability to deal with the central-peripheral fatigue interplay during a more natural form of exercise [ 8 , 15 ], thereby offering insights on the role of the neuromuscular complexity in exercise regulation and pacing strategy.

Whether both central and peripheral fatigue increase as a cycling time trial progresses, one may argue that the neuromuscular complexity decreases as a function of the trial distance [ 16 ].

Consequently, a likely U-shape pacing strategy during a short cycling trial [ 17 ] may indicate a reduction in MOEn, what could be related to the trial fatigue status. Importantly, a shorter cycling time trial may be preferable to emphasize the CNS complexity when regulating the motor output during exercise, given that the magnitude of neural drive required to complete a short time trial such as 4km TT 4km is greater than the neural drive necessary to complete longer ones e.

In this sense, a higher power output could suggest an enhanced motor unit firing synchronization during exercise, as the electromyography EMG entropy is lower in higher i. Therefore, considering that trained cyclists produce a higher mean power output in short TT 4km than in long cycling time trials i.

Some ergogenic aids could add valuable information to the neuromuscular complexity-cycling paradigm, as some ergogenics have the ability to change neuromuscular properties.

For example, caffeine may be an interesting approach to investigate the MOEn-fatigue interplay, indicating if fluctuations in power output responses during cycling time trials may be related to changes in neuromuscular response complexity.

It has been suggested that caffeine increases MOEn through amplification of the synaptic inputs to α-motor neurons [ 19 ].

Caffeine increases the monoamines synthesis and turnover [ 20 ], thereby amplifying the synaptic input and motoneuronal gain [ 21 , 22 ] as indicated by a steeper H-reflex curve and greater self-sustained motor unit firing frequency [ 22 , 23 ].

Consequently, assuming that a higher motor neuron gain is associated with a greater muscle force variability as suggested elsewhere [ 24 ], one may hypothesize that caffeine increases MOEn through increased neuromuscular complexity.

Assuming this hypothesis is right, one may also expect that caffeine may further attenuate the fatigue-induced reduction in MOEn as the trial progresses, thereby likely improving power output and performance [ 25 ]. Therefore, the present study aimed to characterize MOEn in a TT 4km and verify if caffeine ingestion increases power output complexity and performance in this trial.

We hypothesized that caffeine would attenuate a fatigue-induced reduction in power output complexity, improving power output and performance during TT 4km.

Nine endurance-trained male cyclists kg min -1 , having a minimum 3 years training experience competing at regional competitions, classified as performance level 3 [ 26 ] and experienced in cycling time trials, volunteered to participate in this study.

They were non-smokers and had no neuromuscular or cardiopulmonary disorder that could affect the study outcomes. The experimental procedures were previously approved by the Research Ethics Committee of the University of São Paulo After a preliminary visit to obtain anthropometric measures and assess the VO 2MAX through a maximal incremental cycling exercise performed with a 80 rpm pedal cadence 25 W·min -1 increases until exhaustion , cyclists attended to 3 sessions in a counterbalanced order; 1 a baseline 4 km cycling time trial TT 4km ; 2 a TT 4km after caffeine ingestion; 3 a TT 4km after placebo ingestion.

All visits were interspersed by a ~7 days interval. The cyclists were encouraged to maintain the training schedule intensity and volume throughout the study period and avoid vigorous exercise, alcohol, and stimulant or caffeine beverages for the last 24 h before the sessions.

Briefly, we chose a TT 4km as a strenuous whole-body self-paced exercise and assumed that endurance-trained cyclists complete this trial having a mean power output higher than W [ 15 , 16 ], therefore potentiating a likely reduction in MOEn [ 18 ].

In contrast, caffeine ingestion may increase MOEn and TT 4km performance. Caffeine and placebo capsules 6 mg. kg -1 of body mass were ingested ~ 60 min before the TT 4km commencement.

Caffeine and sucrose-based i. placebo substances were formulated in opaque capsules of equal size, color and taste to prevent that participants rightly guessed the treatment. Importantly, instead of a double-blind, randomized placebo-controlled clinical trial, we used a placebo-deceived design, as some have argued that the use of double-blind designs is a possible source of bias in clinical trials [ 29 , 30 ].

To ensure that eventual differences between caffeine and placebo were solely due to caffeine pharmacological effects, cyclists were led to believe they ingested caffeine in both sessions and the study was investigating the reproducibility of caffeine effects on TT 4km performance. They were informed about the presence of a placebo condition at the study completion, as reported elsewhere [ 31 ].

Informal and anecdotal communication revealed that participants were blinded about the presence of a true placebo pill. All cyclists performed the TT 4km on the same road bike Giant®, Thousand Oaks, CA, USA attached to a cycle-simulator calibrated before every test Racer Mate®, Computrainer, Seattle, WA, EUA , individually fitted with crank, pedals and saddle.

This equipment provided power output measures W at a 2Hz sampling rate. The validity and reliability of this system have been previously reported [ 32 , 33 ]. Cyclists performed a standard 7 min warm-up, consisting of a 5 min self-paced gear and cadence freely adjusted and a 2 min controlled-pace cycling fixed gear at W and 80 rpm pedal cadence.

When they were still cycling at the end of the controlled-pace warmup, they immediately started the TT 4km. The cyclists were oriented to rate their perceived exertion RPE at each 0. A researcher unaware of the substance ingested encouraged the cyclists to complete the distance as fast as possible, while distance feedback was available to cyclists to pace themselves.

The entropy could be interpreted as a non-linear analysis that provides a measure of the complexity of a system [ 35 ]. Based on the information theory, entropy is a measure that reflects the level of uncertainty of a dataset or time series. Entropy can be obtained as the probability p k of each possible event multiplied by log of the inverse probability of each event [ 36 ] as described in Eq 1.

However, the prior knowledge of the probability p k for the occurrence of all events is impossible in stochastic processes, therefore, adequate methodologies such as the sample entropy SampEn have been suggested [ 37 ]. The SampEn Eq 2 fits the approximate entropy [ 38 ] to generate less time series length-dependence and self-matching-reduced bias Eq 2.

Where m is the length of sequences to be compared, r is the tolerance for accepting matches and N is the length of the time series. In the SampEn algorithm, r is multiplied by the standard deviation SD of N , providing a matching threshold and allowing comparisons among sequences of m points.

Readers are referred to a seminal work by Richman et al. In this study MOEn was estimated applying SampEn algorithm in the mechanical power output signal obtained during TT 4km. A custom code Matlab v. This improved power output in caffeine was reflected in ~1.

Additionally, cyclists presented comparable mean RPE during the TT 4km in both supplementations with caffeine 16 ± 0. and placebo 16 ± 0. Mechanical power output panel A and motor output entropy panel B in placebo and caffeine trials.

Mechanical power output relative to a percentage of the TT 4km distance. Fig 3 depicts MOEn responses during the cycling trial, and Table 1 shows individual power output and MOEn responses over the TT 4km in both supplementations.

Motor output entropy was expressed relative to a percentage of the TT 4km distance. Table 2 shows all correlation coefficients between MOEn and power output.

This study aimed to characterize the MOEn during a TT 4km and investigate if caffeine could change the MOEn-fatigue interplay during this strenuous, whole-body short cycling exercise.

Our results showed a progressive reduction in motor output complexity as the TT 4km progressed, however caffeine increased TT 4km performance through an altered MOEn-fatigue interplay. These results may support the notion that caffeine increases power output responses and attenuates the fatigue-induced reduction in MOEn during TT 4km.

This is the first study characterizing the MOEn during a natural exercise mode with high ecological validity such as a strenuous, whole-body short cycling time trial. Briefly, MOEn responses could involve changes in neuromuscular complexity such as in CNS areas such as cortical, subcortical and spinal areas, as well as in motor neuron conduction to skeletal muscles.

However, despite the increasing exercise-induced perturbation, neuromuscular fatigue was likely low over this half of the trial and probably allowed an increased MOEn when regulating the motor output during this part [ 40 ].

One may argue that neuromuscular fatigue is low during this initial part of the trial, thus likely allowing an adequate response of the neuromuscular system to the exercise-imposed perturbation through an increased motor unit firing variability. In contrast, such a correlation between power output and MOEn was not observed in placebo TT 4km during these parts.

Muscle glycogen content was manipulated via exercise—diet interventions so that two experimental trials were commenced with LOW and two with NORM muscle glycogen availability. Sixty minutes before an experimental trial, subjects ingested a capsule containing anhydrous caffeine CAFF, 3 mg-1·kg-1 body mass or placebo PLBO.

Instantaneous power output was measured throughout high-intensity interval training 8 × 5-min bouts at maximum self-selected intensity with 1-min recovery. Results There were significant main effects for both preexercise glycogen content and caffeine ingestion on power output.

Conclusion We conclude that caffeine enhanced power output independently of muscle glycogen concentration but could not fully restore power output to levels commensurate with that when subjects commenced exercise with normal glycogen availability.

However, the reported increase in power output does provide a likely performance benefit and may provide a means to further enhance the already augmented training response observed when selected sessions are commenced with reduced muscle glycogen availability. Accumulating evidence now suggests that many of these adaptations can be modified by nutrient availability 9—11, Of note is that the superior training adaptation in these previous studies was attained despite a reduction in maximal self-selected power output 16, The most obvious factor underlying the reduced intensity during a second training bout is the reduction in muscle glycogen availability.

Regardless of the precise mechanism s , there remains the intriguing possibility that the magnitude of training adaptation previously reported in the face of a reduced training intensity Hulston et al.

Recent evidence suggests that, at least in endurance-based events, the maximal benefits of caffeine are seen at small to moderate 2—3 mg·kg-1 body mass BM doses for reviews, see Refs.

Accordingly, in this study, we aimed to determine the effect of a low dose of caffeine 3 mg·kg-1 BM on maximal self-selected power output during HIT commenced with either normal NORM or low LOW muscle glycogen availability. We hypothesized that even under conditions of low glycogen availability, caffeine would increase maximal self-selected power output and thereby partially rescue the reduction in training intensity observed when individuals commence HIT with low glycogen availability.

Journal Caffeine and power output Caffeime International Society of Sports Nutrition volume outlutArticle Nutritious meal options 11 Cite this article. Metrics details. Caffeine is commonly used as ;ower Caffeine and power output aid. Literature about the effects of caffeine ingestion on muscle strength and power is equivocal. The aim of this systematic review and meta-analysis was to summarize results from individual studies on the effects of caffeine intake on muscle strength and power. A search through eight databases was performed to find studies on the effects of caffeine on: i maximal muscle strength measured using 1 repetition maximum tests; and ii muscle power assessed by tests of vertical jump.

Author: Douzahn

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