International Journal of Sports Physiology and Performance, 2015, 10, 897 -901 http://dx.doi.org/10.1123/ijspp.2014-0481 © 2015 Human Kinetics, Inc.
Original Investigation
The Effects of Red Bull Energy Drink Compared With Caffeine on Cycling Time-Trial Performance Alannah Quinlivan, Christopher Irwin, Gary D. Grant, Sheilandra Anoopkumar-Dukie, Tina Skinner, Michael Leveritt, and Ben Desbrow This study investigated the ergogenic effects of a commercial energy drink (Red Bull) or an equivalent dose of anhydrous caffeine in comparison with a noncaffeinated control beverage on cycling performance. Eleven trained male cyclists (31.7 ± 5.9 y 82.3 ± 6.1 kg, V˙O2max = 60.3 ± 7.8 mL · kg–1 · min–1) participated in a double-blind, placebo-controlled, crossover-design study involving 3 experimental conditions. Participants were randomly administered Red Bull (9.4 mL/kg body mass [BM] containing 3 mg/kg BM caffeine), anhydrous caffeine (3 mg/kg BM given in capsule form), or a placebo 90 min before commencing a time trial equivalent to 1 h cycling at 75% peak power output. Carbohydrate and fluid volumes were matched across all trials. Performance improved by 109 ± 153 s (2.8%, P = .039) after Red Bull compared with placebo and by 120 ± 172 s (3.1%, P = .043) after caffeine compared with placebo. No significant difference (P > .05) in performance time was detected between Red Bull and caffeine treatments. There was no significant difference (P > .05) in mean heart rate or rating of perceived exertion among the 3 treatments. This study demonstrated that a moderate dose of caffeine consumed as either Red Bull or in anhydrous form enhanced cycling time-trial performance. The ergogenic benefits of Red Bull energy drink are therefore most likely due to the effects of caffeine, with the other ingredients not likely to offer additional benefit. Keywords: ergogenic, performance enhancement, sport, physiology Caffeine (1,3,7-trimethylxanthine) is one of the most popular and widely accepted ergogenic aids used by athletes in endurance sports.1–3 The ergogenic effect of caffeine on enduranceperformance tasks lasting approximately 1 hour has been well documented.4,5 During research studies, caffeine is usually provided in pure (anhydrous) form in capsules and in doses relative to body mass. However, in practical settings such as sporting competitions, caffeine is usually consumed in foods and beverages.2 When caffeine is consumed in foods and beverages, other coingested ingredients have the potential to influence the ergogenic response to it. The results from studies that have investigated the ergogenic potential of foods containing caffeine as a natural ingredient (eg, coffee) have proven somewhat equivocal.6,7 When the influence of coffee on endurance performance was compared with that of pure caffeine ingestion, Graham et al7 found that caffeine consumed as coffee was not able to enhance endurance-running performance. However, when the same participants ingested an equivalent dose of anhydrous caffeine they significantly improved their run time to exhaustion. Those authors suggested that there were components in coffee that impaired the ergogenic effects of caffeine. Conversely, a recent investigation demonstrated that both anhydrous caffeine and coffee improve endurance performance in trained cyclists compared with trials without caffeine.6 The innate variations in accompanying ingredients in beverages that naturally contain caffeine create the potential for different ergogenic responses to these products. Quinlivan is with the Melbourne Medical School, University of Melbourne, Melbourne, Australia. Irwin, Grant, Anoopkumar-Dukie, and Desbrow are with the Menzies Health Institute Queensland, Griffith University, Gold Coast, Australia. Skinner and Leveritt are with the School of Human Movement Studies, University of Queensland, Brisbane, Australia. Address author correspondence to Ben Desbrow at [email protected].
Commercially manufactured energy drinks are heavily promoted as capable of enhancing performance due to the presence of a range of active ingredients including caffeine. However, evidence for the capacity of these other ingredients (eg, taurine), either alone or in combination with caffeine, to enhance performance is limited.8–10 To date, 5 studies on the ergogenic effect of caffeinated energy drinks on exercise tasks lasting ~60 minutes have been conducted,11–15 with the performance results across all studies being inconclusive. Three studies have been conducted using either an artificially flavored or carbohydrate-containing control beverage.11,13,15 In 2 similar studies conducted by the same research group, the ingestion of an absolute dose (500 mL) of different commercial energy drinks significantly improved cycling time-trial (TT) performance by 3.0% to 4.7%.13,15 Conversely, a study by Umaña-Alvarado and Moncada-Jiménez,11 using a relative dose of energy drink (6 mL/kg body mass [BM]) and a 10-km running protocol, failed to demonstrate any performance change. Unfortunately, as these studies did not include caffeine- and carbohydrate-matched controls, whether the ergogenic response to an energy drink is the result of caffeine and/or carbohydrate (CHO) alone or the combination of caffeine, CHO, and the other energy-drink ingredients cannot be determined. Phillips et al14 recently provided 11 participants with a commercial energy drink (500 mL), a cola beverage matched for CHO and caffeine, or a control beverage without caffeine or CHO before a simulated 25-mile cycle race. Their study failed to demonstrate a performance improvement with either the energy drink or cola beverage relative to the control treatment. The lack of ergogenic response in the caffeinated trials contradicted the authors’ hypothesis and is in disagreement with other studies using pure caffeine with similar exercise tasks.16–18 In a much earlier study, Geiß et al12 provided 10 trained participants with a company-supplied energydrink placebo to investigate if a taurine-enriched energy drink (Red Bull) enhanced time to fatigue after 60 minutes of steady-state 897
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cycling. The design included trials of beverages without taurine, glucuronolactone, or caffeine (control); a drink including caffeine but without taurine or glucuronolactone (caffeine); and the commercial formulation containing all ingredients. Participants cycled significantly longer with commercial formulation than with both the control beverage (24%) and caffeine (8%). A limitation of this study is that time-to-fatigue protocols have been suggested to better serve as tests of exercise capacity rather than absolute performance,19 whereas protocols based on fixed-endpoint tasks (eg, TTs) have greater ecological validity20 and appear to be highly reproducible.21 It is apparent that the effects of caffeinated energy drinks on endurance-exercise performance are somewhat inconsistent, and it is not clear at this stage if additional ingredients other than caffeine and/or CHO influence any ergogenic effect. Therefore, the current study aimed to compare the effects of a popular energy drink (Red Bull) containing a moderate dose of caffeine (3 mg/kg BM) or an equivalent dose of anhydrous caffeine in a CHO-matched beverage in comparison with a noncaffeinated control beverage on endurance-cycling TT performance in trained participants. We hypothesized that both sources of caffeine would enhance performance compared with placebo, but there would be no performance difference between trials employing anhydrous caffeine compared with a caffeinated energy drink.
Methods Participants Initially, 12 well-trained competitive male cyclists and triathletes were recruited for this study. However, 1 participant was forced to withdraw after the initial trial due to severe stomach pains experienced after consuming Red Bull. The remaining 11 participants (age 31.6 ± 6.1 y, body mass 82.6 ± 6.3 kg, V˙O2max 60.7 ± 8.1 mL · kg–1 · min–1, peak power output 401.8 ± 31.4 W) completed all aspects of the study. The participants were nonsmokers and regular caffeine consumers (mean caffeine consumption 271 ± 29 5 mg/d). Seven participants were regular consumers of energy drinks (with 6 regularly drinking Red Bull), and 4 consistently used them before or during competition. This study was conducted in accordance with the procedures approved by the human research ethics committee of Griffith University, and all potential recruits provided written informed consent before research participation.
Preexperimental Protocol Each participant reported to the laboratory on 6 separate occasions. During the first visit, participants underwent an incremental test to exhaustion on an electronically braked cycle ergometer (Lode Instruments, Groningen, Netherlands) to establish their maximal oxygen uptake (V˙O2max) and peak power output. The V˙O2max test (previously described by Desbrow et al22) began with 5 minutes cycling at 100 W and increased by 50 W every 2.5 minutes until exhaustion. Participants were fitted with a mouthpiece to measure expired gases (O2 and CO2) through a calibrated metabolic measuring system (MedGraphics, St Paul, MN, USA). After the initial visit, participants returned to the laboratory on 2 separate occasions to complete familiarization sessions that simulated trial procedures with the exception of blood-sample collection. The primary aim of these familiarization sessions was to reduce the practice or learning effect, but they also allowed participants to become familiar with test equipment and procedures and to establish a self-selected warm-up that would be replicated throughout the trials.
Experimental Protocol After completion of the familiarization sessions, all participants completed 3 experimental trials that consisted of a TT lasting approximately 1 hour and were separated by at least 7 days. The order of the experimental trials was randomized by a person independent to the study using an incomplete Latin-square design. In the 24 hours preceding each trial, participants were required to abstain from strenuous exercise, alcohol, and all sources of caffeine. Each participant received a standardized prepackaged diet to follow for 24 hours before each trial, which aimed to provide 200 kJ/kg BM, including 7.5 g/kg BM of CHO, following the recommendations for dietary standardization in previous studies.23,24 There were no restrictions placed on participants with regard to water consumption. All trials were completed in a stable laboratory environment (19°C ± 2°C, ~55% relative humidity) at the same time of day. On the morning of the trial, participants reported to the laboratory after an overnight fast (commencing from 8 PM). Immediately on arrival approximately 5 mL of blood was collected via forearm venipuncture for plasma caffeine analysis to ensure compliance with caffeine abstinence. The treatment, which consisted of 9.4 mL/kg BM of energy drink (either Red Bull [Red Bull GmbH, Austria] or CHO-matched placebo) and capsules (either anhydrous caffeine [PCCA, USA] or placebo), was provided to participants immediately after the blood collection. Participants were then given a pretrial meal in the form of 1.5 g/kg BM of Powerbar, which in combination with the energy drink ensured that they ingested 42 kJ/kg BM with approximately 2 g/kg BM of CHO before the TT. Dietary compliance was confirmed via a checklist followed by a brief questionnaire on the level of gastric discomfort (if any) the participant experienced. Participants were then required to rest quietly for ~90 minutes. They completed their preselected warmup, during which time they were provided with ~3 mL/kg BM of commercial sports drink (Gatorade). This warm-up was followed by collection of another 5 mL of blood via forearm venipuncture, which occurred 90 minutes after treatment ingestion. The exercise protocol used was a TT lasting ~1 hour, as described by Jeukendrup et al,21 in which participants aimed to complete a set amount of work as quickly as possible. The amount of work participants were required to perform was the equivalent of 60 minutes cycling at 75% of individual peak power output (as calculated in the incremental test to exhaustion). Performance times, heart-rate (HR) values, and ratings of perceived exertion (RPE) (using the Borg scale) were recorded at every 10% of work completed, 95%, and 99%, as well as at immediate completion of each trial. HR values were obtained using an HR monitor (Polar Electro, Kempele, Finland). Participants were provided with 3 mL/kg BM of Gatorade at 30% and 60% of work completed. Immediately after completing each trial, participants were asked to quantify any gastric discomfort experienced (on a scale of 1–10), as well as any leg-muscle pain, using a category scale previously described.25,26 A final 5-mL blood sample was taken via forearm venipuncture exactly 5 minutes after completion of the TT, and participants were asked to complete a brief questionnaire regarding their perceived performance and which treatment they believed they had received. All collected blood samples were kept in a lithium heparin Vacutainer to prevent coagulation before centrifugation at 3200 rpm for 10 minutes at 4°C. The plasma was then stored at –84°C to await analysis. Determination of plasma caffeine was undertaken using reverse-phase high-performance liquid chromatography (HPLC) analysis. The concentration of caffeine was quantified through
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extrapolation from calibration curves generated on the day of analysis. The protocol for identification and quantification of caffeine was adapted from HPLC conditions previously reported,27 and the coefficients of variation were >5% for accuracy and repeatability. Analysis of plasma glucose concentrations was conducted using the COBAS Integra 400+ automated blood analyzer. The coefficient of variation with regard to glucose analysis was 0.4% at 4.5 mmol/L and 0.5% at 12.5 mmol/L.
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Supplementation Red Bull energy drink and the placebo were matched for energy (185 kJ/100 mL), CHO (11 g/100 mL), and volume (9.4m L/kg BM). The placebo employed for this trial was concentrated Gatorade powder (Fierce Berry) mixed with carbonated water (SodaStream). Treatments were administered in opaque bottles, and a small amount of pink food coloring was added to the Red Bull drink to mask the difference in color of the 2 drinks. Drinks were prepared in advance by an independent researcher so that both participants and investigators were unaware of the contents of each drink. Participants were informed they would be receiving either caffeine or an energy drink for each trial and were not given any information relating to the possible contents of the drinks, with the research team referring to them as only “energy drinks.” The same volume of beverage used for the initial trial was used for subsequent trials. The placebo capsule consisted of a similar volume of Metamucil. The presence of a placebo trial was only mentioned at the completion of the 3 trials before the final survey.
in comparison with placebo (Table 1). The mean TT times for the placebo, caffeine, and Red Bull trials indicate that ingestion of 3 mg/ kg BM caffeine resulted in an improvement of 120 ± 172 seconds (3.1%) while Red Bull ingestion improved performance by 109 ± 153 seconds (2.8%) (Table 1). Mean power output was increased in Red Bull and caffeine treatments versus placebo, which corresponds to the improvements in performance times in both trials. Eight of the eleven participants recorded their slowest times during the placebo trial.
HR, RPE, and Quadriceps Muscle Pain While there was a trend toward higher mean HR values and quadriceps muscle pain in caffeine and Red Bull trials (HR, caffeine vs placebo P = .068 and Red Bull vs placebo P = .086; leg pain, caffeine vs placebo P = .085 and Red Bull vs placebo P = .052) compared
Statistical Analysis All statistical data collected were analyzed using the statistical software package IBM SPSS statistics 19 (Chicago, IL). Time to completion and quadriceps muscle pain were analyzed using a 1-way repeated-measures analysis of variance (ANOVA), while plasma caffeine, lactate, and glucose, as well as HR and RPE, were analyzed using a 2-way repeated-measures ANOVA. Pairwise comparisons between caffeinated beverages and the placebo trial were performed, and where significant main effects were observed, post hoc analysis was undertaken (Fischer least significant difference). All data are reported as mean ± SD. Statistical significance was taken as P < .05.
Figure 1 — Plasma caffeine concentrations across all trials.
Table 1 Effect of Ingesting a Commercial Energy Drink Before a Simulated 40-km Cycling Time Trial Compared With Anhydrous Caffeine or a Placebo Control Total time (s)
Results
Mean power output (W)
Placebo
Red Bull
Caffeine
3877 ± 260
3768 ± 257*
3757 ± 278*
287 ± 31
300 ± 30*
295 ± 31*
Heart rate (beats/min)
Standardization
rest
79.6 ± 13.6
76.1 ± 14.8
78.9 ± 12.4
Good compliance with both dietary and exercise-related standardizations were achieved by participants in the 24 hours preceding each trial. The mean dietary intake reported was 199 ± 26 kJ/kg BM energy and 7.3 ± 0.7 g/kg BM CHO. Participants also reported no consumption of alcohol during this time in addition to no strenuous exercise for 18 hours before each trial. Analysis of the initial plasma caffeine samples revealed no detectable caffeine (Figure 1), indicating that all participants successfully abstained from caffeine in the 24 hours preceding each trial. The mean volume of beverage consumed 90 minutes before exercise was 776 ± 59 mL.
mean
168.1 ± 10.0
171.6 ± 9.7
171.4 ± 8.9
100% work completed
172.9 ± 11.4
176.4 ± 10.4
176.7 ± 9.5
mean
15.2 ± 1.2
15.7 ± 1.1
15.3 ± 1.0
100% work completed
17.6 ± 1.4
17.9 ± 1.5
17.8 ± 1.4
Quadriceps muscle pain postexercise (1–10)
4.4 ± 1.3
5.4 ± 1.9
5.4 ± 1.7
predrink
5.4 ± 1.0
5.1 ± 0.6
5.1 ± 0.8
Performance
preexercise
4.1 ± 1.7
4.7 ± 1.6
3.6 ± 0.8
Time to complete the TT was significantly improved after ingestion of both caffeine (P = .043) and Red Bull (P = .039) treatments
postexercise
6.4 ± 0.7
6.6 ± 1.6
6.9 ± 1.8
RPE (6–20)
Blood glucose (mmol/L)
*P < .05 vs placebo.
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with placebo conditions, these values failed to reach statistical significance. No significant difference in RPE was observed when caffeine-containing trials were compared with the placebo trial.
Gastric Discomfort Gastric discomfort with a rating of >5 out of 10 was experienced by 2 participants after Red Bull ingestion (in addition to the 1 participant who withdrew from the study). These participants described the symptoms as “sharp/stabbing” or “regurgitating” with some associated nausea. Despite these reports, the participants’ performance on the Red Bull trial was faster than during the caffeine trial. Only minor (≤3 out of 10) ratings of gastrointestinal discomfort were reported in other trials.
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Plasma Caffeine and Glucose Acute ingestion of both caffeine and Red Bull resulted in significant increases in plasma caffeine concentrations (P < .05). There was no significant difference (all values P > .05) detected between caffeine and Red Bull treatments either immediately before or after the trials. Blood glucose was not significantly different (all P > .05) between the 3 conditions (Table 1).
Blinding No participant reported certainty about all treatment being administered. Only 1 participant correctly determined the order of all treatments. Three participants correctly identified the trial in which they received Red Bull; however, only 1 participant was certain of this choice. Five participants believed they received Red Bull after being administered the alternative drink (3 during the placebo trial, 2 during caffeine trial). Eight participants thought they were given an alternative caffeinated energy drink (not Red Bull) during all 3 trials.
Discussion The aim of this study was to compare the effects of a commercially available energy drink with an equivalent dose of anhydrous caffeine (3 mg/kg BM) on endurance-cycling TT performance undertaken after exercise and dietary control. Consistent with our hypothesis, we found that both Red Bull and anhydrous caffeine enhanced TT performance compared with placebo in trained, familiarized, and fed participants. This suggests that the ergogenic effects associated with Red Bull consumption relate directly to the beverage’s caffeine content. The magnitude of performance improvements observed due to caffeine (3.1%) and Red Bull (2.8%) treatments are comparable to many,16–18 but not all,14 previous studies investigating the ergogenic effects of caffeine on cycle TT performance lasting ~60 minutes. Indeed, the mean performance improvement calculated after a systematic review of endurance studies using TT-type protocols indicated an improvement of 2.3% ± 3.2% when caffeine was ingested before exercise.4 The outcome from the recent study by Phillips et al14 somewhat contradict the findings from the current study. Phillips et al14 failed to demonstrate any performance improvement relative to a control when ingesting either an energy drink or a CHO- and caffeine-matched cola beverage before undertaking an endurance-cycling TT. The differing results may, in part, be explained by differences in the methods employed. The protocol by Phillips et al14 used a smaller (~2 mg/kg BM) absolute caffeine dose. Previous studies have suggested that the
ergogenic effects of caffeine increase as doses increase up to ~3 mg/ kg BM, with no further increase above this dose.17,28,29 In addition, the participants had, on average, lower aerobic capacity (52 vs 60 mL · kg–1 · min-1), and the use of drinks with clearly different flavor profiles denotes that expectancy effects cannot be entirely excluded. The studies do, however, concur that no performance differences are evident between the ingestion of an energy drink and that of a beverage with matching amounts of caffeine and CHO. Alongside CHO and caffeine, other (secondary) ingredients with the potential to influence performance in Red Bull include taurine, glucuronolactone, and B-complex vitamins. Limited research examining the effect of these secondary ingredients on mechanisms underpinning endurance performance and/or performance itself exists. Indeed, taurine, glucuronolactone, and B-complex vitamins do not appear to substantially alter aerobic metabolism when consumed as a combination30 or in isolation (ie, taurine only)31,32 (no investigations using isolated glucuronolactone or B-complex vitamins were identified). The current results suggest that secondary ingredients in energy drinks do not influence blood glucose, plasma caffeine, quadriceps muscle pain, HR, or RPE when compared with the same dose of pure caffeine delivered before an endurance task. Furthermore, when measured, any effect of the secondary ingredients on endurance-exercise performance appear small32 or absent (current study and that of Rutherford et al31). This suggests that trained individuals consuming caffeinated energy drinks in an attempt to improve endurance performance lasting ~1 hour receive minimal, if any, additional benefit from the other constituents contained in Red Bull.
Practical Application The volume of a caffeinated energy drink required to provide a 3-mg/kg BM dose of caffeine is substantial (~3 × 250-mL cans). It is important to note that a number of participants in the current study experienced severe stomach pains during the Red Bull trials, which were not observed when the same volume of fluid and amount of CHO was consumed in the caffeine and placebo trials. The potential for specific ingredients in energy drinks to cause gastrointestinal discomfort during exercise warrants further consideration. Clearly, using energy drinks as the mode of caffeine delivery for performance enhancement will require consideration of the volume needed, palatability, and event characteristics (eg, duration and/or mode of exercise), which may all affect potential gastrointestinal tolerance.
Conclusions This study demonstrated that a moderate dose of caffeine consumed via Red Bull energy drink or anhydrous caffeine enhance endurance-cycling TT performance by a similar magnitude. The ergogenic effect of the energy drink is therefore most likely the result of its caffeine content, with the other ingredients offering no further benefit. Acknowledgments Funding for this investigation was provided from internal Griffith University support.
References 1. Desbrow B, Leveritt M. Well-trained endurance athletes’ knowledge, insight, and experience of caffeine use. Int J Sport Nutr Exerc Metab. 2007;17(4):328–339. PubMed
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2. Desbrow B, Leveritt M. Awareness and use of caffeine by athletes competing at the 2005 Ironman Triathlon World Championships. Int J Sport Nutr Exerc Metab. 2006;16(5):545–558. PubMed 3. Del Coso J, Muñoz G, Muñoz-Guerraa J. Prevalence of caffeine use in elite athletes following its removal from the World AntiDoping Agency list of banned substances. Appl Physiol Nutr Metab. 2011;36:555–561. PubMed doi:10.1139/h11-052 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. 2009;23(1):315–324. PubMed doi:10.1519/ JSC.0b013e31818b979a 5. Doherty M, Smith P. Effects of caffeine ingestion on ratings of perceived exertion during and after exercise: a meta-analysis. Scand J Med Sci Sports. 2005;15:69–78. PubMed doi:10.1111/j.16000838.2005.00445.x 6. Hodgson AB, Randell RK, Jeukendrup AE. The metabolic and performance effects of caffeine compared to coffee during endurance exercise. PLoS One. 2013;8(4):e59561. PubMed doi:10.1371/journal. pone.0059561 7. Graham TE, Hibbert E, Sathasivam P. Metabolic and exercise endurance effects of coffee and caffeine ingestion. J Appl Physiol. 1998;85(3):883–889. PubMed 8. Shearer J, Graham T. Caffeine and caffeinated energy drink consumption: a systematic review of performance and metabolic consequences on glucose disposal. Nutr Rev. 2014; in press. doi:10.1111/nure.12124 9. McLellan TM, Lieberman HR. Do energy drinks contain active components other than caffeine? Nutr Rev. 2012;70(12):730–744. PubMed doi:10.1111/j.1753-4887.2012.00525.x 10. Heneghan C, Gill P, O’Neill B, Lasserson D, Thake M, Thompson M. Mythbusting sports and exercise products. BMJ. 2012;345:e4848. PubMed doi:10.1136/bmj.e4848 11. Umaña-Alvarado M, Moncada-Jiménez J. Consumption of an ‘energy drink’ does not improve aerobic performance in male athletes. Int J Appl Sports Sci. 2005;17(2):26–34. 12. Geiß KR, Jester I, Falke W, Hamm M, Waag KL. The effect of a taurine-containing drink on performance in 10 endurance-athletes. Amino Acids. 1994;7(1):45–56. PubMed doi:10.1007/BF00808445 13. Ivy JL, Kammer L, Ding ZP, et al. Improved cycling time-trial performance after ingestion of a caffeine energy drink. Int J Sport Nutr Exerc Metab. 2009;19(1):61–78. PubMed 14. Phillips MD, Rola KS, Christensen KV, Ross JW, Mitchell JB. Preexercise energy drink consumption does not improve endurance cycling performance but increases lactate, monocyte, and interleukin-6 response. J Strength Cond Res. 2014;28(5):1443–1453. PubMed doi:10.1519/JSC.0000000000000275 15. Lassiter D, Kammer L, Burns J, et al. Effect of an energy drink on physical and cognitive performance in trained cyclists. J Caff Res. 2012;2(4):167–175. doi:10.1089/jcr.2012.0024 16. Irwin C, Desbrow B, Ellis A, O’Keeffe B, Grant G, Leveritt M. Caffeine withdrawal and high-intensity endurance cycling performance. J Sports Sci. 2011;29(5):509–515. PubMed 17. Desbrow B, Biddulph C, Devlin B, Grant GD, Anoopkumar-Dukie S, Leveritt MD. The effects of different doses of caffeine on endurance
cycling time trial performance. J Sports Sci. 2012;30(2):115–120. PubMed doi:10.1080/02640414.2011.632431 18. McNaughton LR, Lovell RJ, Siegler J, Midgley AW, Moore L, Bentley DJ. The effects of caffeine ingestion on time trial cycling performance. Int J Sports Physiol Perform. 2008;3(2):157–163. PubMed 19. Burke LM. Caffeine and sports performance. Appl Physiol Nutr Metab. 2008;33(6):1319–1334. PubMed doi:10.1139/H08-130 20. Currell K, Jeukendrup AE. Validity, reliability and sensitivity of measures of sporting performance. Sports Med. 2008;38(4):297–316. PubMed doi:10.2165/00007256-200838040-00003 21. Jeukendrup A, Saris W, Brouns F, Arnold D. A new validated endurance performance test. Med Sci Sports Exerc. 1996;28:266–270. PubMed doi:10.1097/00005768-199602000-00017 22. Desbrow B, Minahan C, Leveritt M. Drink-flavor change’s lack of effect on endurance cycling performance in trained athletes. Int J Sport Nutr Exerc Metab. 2007;17(4):315–327. 23. Burke LM, Cox G, Cummings N, Desbrow B. Guidelines for daily carbohydrate intake: do athletes achieve them? Sports Med. 2001;31(4):267–299. PubMed doi:10.2165/00007256-20013104000003 24. Jeacocke NA, Burke LM. Methods to standardize dietary intake before performance testing. Int J Sport Nutr Exerc Metab. 2010;20(2):87– 103. PubMed 25. Cook DB, O’Connor PJ, Eubanks SA, Smith JC, Lee M. Naturally occurring muscle pain during exercise: assessment and experimental evidence. Med Sci Sports Exerc. 1997;29(8):999–1012. PubMed doi:10.1097/00005768-199708000-00004 26. Stuart GR, Hopkins W, Cook C, Cairns S. Multiple effects of caffeine on simulated high-intensity team-sport performance. Med Sci Sports Exerc. 2005;37(11):1998–2005. PubMed doi:10.1249/01. mss.0000177216.21847.8a 27. Perera V, Gross AS, McLachlan AJ. Caffeine and paraxanthine HPLC assay for CYP1A2 phenotype assessment using saliva and plasma. Biomed Chromatogr. 2010;24(10):1136–1144. PubMed doi:10.1002/ bmc.1419 28. Kovacs EM, Stegen J, Brouns F. Effect of caffeinated drinks on substrate metabolism, caffeine excretion and performance. J Appl Physiol. 1998;85(2):709–715. PubMed 29. Jenkins NT, Trilk JL, Singhal A, O’Connor PJ, Cureton KJ. Ergogenic effects of low doses of caffeine on cycling performance. Int J Sport Nutr Exerc Metab. 2008;18(3):328–342. PubMed 30. Pettitt RW, Niemeyer JD, Sexton PJ, Lipetzky A, Murray SR. Do the noncaffeine ingredients of energy drinks affect metabolic responses to heavy exercise? J Strength Cond Res. 2013;27(7):1994–1999. PubMed doi:10.1519/JSC.0b013e3182736e31 31. Rutherford JA, Spriet LL, Stellingwerff T. The effect of acute taurine ingestion on endurance performance and metabolism in welltrained cyclists. Int J Sport Nutr Exerc Metab. 2010;20(4):322–329. PubMed 32. Balshaw TG, Bampouras TM, Barry TJ, Sparks SA. The effect of acute taurine ingestion on 3-km running performance in trained middle-distance runners. Amino Acids. 2013;44(2):555–561. PubMed doi:10.1007/s00726-012-1372-1
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Original Investigation
The Effects of Red Bull Energy Drink Compared With Caffeine on Cycling Time-Trial Performance Alannah Quinlivan, Christopher Irwin, Gary D. Grant, Sheilandra Anoopkumar-Dukie, Tina Skinner, Michael Leveritt, and Ben Desbrow This study investigated the ergogenic effects of a commercial energy drink (Red Bull) or an equivalent dose of anhydrous caffeine in comparison with a noncaffeinated control beverage on cycling performance. Eleven trained male cyclists (31.7 ± 5.9 y 82.3 ± 6.1 kg, V˙O2max = 60.3 ± 7.8 mL · kg–1 · min–1) participated in a double-blind, placebo-controlled, crossover-design study involving 3 experimental conditions. Participants were randomly administered Red Bull (9.4 mL/kg body mass [BM] containing 3 mg/kg BM caffeine), anhydrous caffeine (3 mg/kg BM given in capsule form), or a placebo 90 min before commencing a time trial equivalent to 1 h cycling at 75% peak power output. Carbohydrate and fluid volumes were matched across all trials. Performance improved by 109 ± 153 s (2.8%, P = .039) after Red Bull compared with placebo and by 120 ± 172 s (3.1%, P = .043) after caffeine compared with placebo. No significant difference (P > .05) in performance time was detected between Red Bull and caffeine treatments. There was no significant difference (P > .05) in mean heart rate or rating of perceived exertion among the 3 treatments. This study demonstrated that a moderate dose of caffeine consumed as either Red Bull or in anhydrous form enhanced cycling time-trial performance. The ergogenic benefits of Red Bull energy drink are therefore most likely due to the effects of caffeine, with the other ingredients not likely to offer additional benefit. Keywords: ergogenic, performance enhancement, sport, physiology Caffeine (1,3,7-trimethylxanthine) is one of the most popular and widely accepted ergogenic aids used by athletes in endurance sports.1–3 The ergogenic effect of caffeine on enduranceperformance tasks lasting approximately 1 hour has been well documented.4,5 During research studies, caffeine is usually provided in pure (anhydrous) form in capsules and in doses relative to body mass. However, in practical settings such as sporting competitions, caffeine is usually consumed in foods and beverages.2 When caffeine is consumed in foods and beverages, other coingested ingredients have the potential to influence the ergogenic response to it. The results from studies that have investigated the ergogenic potential of foods containing caffeine as a natural ingredient (eg, coffee) have proven somewhat equivocal.6,7 When the influence of coffee on endurance performance was compared with that of pure caffeine ingestion, Graham et al7 found that caffeine consumed as coffee was not able to enhance endurance-running performance. However, when the same participants ingested an equivalent dose of anhydrous caffeine they significantly improved their run time to exhaustion. Those authors suggested that there were components in coffee that impaired the ergogenic effects of caffeine. Conversely, a recent investigation demonstrated that both anhydrous caffeine and coffee improve endurance performance in trained cyclists compared with trials without caffeine.6 The innate variations in accompanying ingredients in beverages that naturally contain caffeine create the potential for different ergogenic responses to these products. Quinlivan is with the Melbourne Medical School, University of Melbourne, Melbourne, Australia. Irwin, Grant, Anoopkumar-Dukie, and Desbrow are with the Menzies Health Institute Queensland, Griffith University, Gold Coast, Australia. Skinner and Leveritt are with the School of Human Movement Studies, University of Queensland, Brisbane, Australia. Address author correspondence to Ben Desbrow at [email protected].
Commercially manufactured energy drinks are heavily promoted as capable of enhancing performance due to the presence of a range of active ingredients including caffeine. However, evidence for the capacity of these other ingredients (eg, taurine), either alone or in combination with caffeine, to enhance performance is limited.8–10 To date, 5 studies on the ergogenic effect of caffeinated energy drinks on exercise tasks lasting ~60 minutes have been conducted,11–15 with the performance results across all studies being inconclusive. Three studies have been conducted using either an artificially flavored or carbohydrate-containing control beverage.11,13,15 In 2 similar studies conducted by the same research group, the ingestion of an absolute dose (500 mL) of different commercial energy drinks significantly improved cycling time-trial (TT) performance by 3.0% to 4.7%.13,15 Conversely, a study by Umaña-Alvarado and Moncada-Jiménez,11 using a relative dose of energy drink (6 mL/kg body mass [BM]) and a 10-km running protocol, failed to demonstrate any performance change. Unfortunately, as these studies did not include caffeine- and carbohydrate-matched controls, whether the ergogenic response to an energy drink is the result of caffeine and/or carbohydrate (CHO) alone or the combination of caffeine, CHO, and the other energy-drink ingredients cannot be determined. Phillips et al14 recently provided 11 participants with a commercial energy drink (500 mL), a cola beverage matched for CHO and caffeine, or a control beverage without caffeine or CHO before a simulated 25-mile cycle race. Their study failed to demonstrate a performance improvement with either the energy drink or cola beverage relative to the control treatment. The lack of ergogenic response in the caffeinated trials contradicted the authors’ hypothesis and is in disagreement with other studies using pure caffeine with similar exercise tasks.16–18 In a much earlier study, Geiß et al12 provided 10 trained participants with a company-supplied energydrink placebo to investigate if a taurine-enriched energy drink (Red Bull) enhanced time to fatigue after 60 minutes of steady-state 897
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cycling. The design included trials of beverages without taurine, glucuronolactone, or caffeine (control); a drink including caffeine but without taurine or glucuronolactone (caffeine); and the commercial formulation containing all ingredients. Participants cycled significantly longer with commercial formulation than with both the control beverage (24%) and caffeine (8%). A limitation of this study is that time-to-fatigue protocols have been suggested to better serve as tests of exercise capacity rather than absolute performance,19 whereas protocols based on fixed-endpoint tasks (eg, TTs) have greater ecological validity20 and appear to be highly reproducible.21 It is apparent that the effects of caffeinated energy drinks on endurance-exercise performance are somewhat inconsistent, and it is not clear at this stage if additional ingredients other than caffeine and/or CHO influence any ergogenic effect. Therefore, the current study aimed to compare the effects of a popular energy drink (Red Bull) containing a moderate dose of caffeine (3 mg/kg BM) or an equivalent dose of anhydrous caffeine in a CHO-matched beverage in comparison with a noncaffeinated control beverage on endurance-cycling TT performance in trained participants. We hypothesized that both sources of caffeine would enhance performance compared with placebo, but there would be no performance difference between trials employing anhydrous caffeine compared with a caffeinated energy drink.
Methods Participants Initially, 12 well-trained competitive male cyclists and triathletes were recruited for this study. However, 1 participant was forced to withdraw after the initial trial due to severe stomach pains experienced after consuming Red Bull. The remaining 11 participants (age 31.6 ± 6.1 y, body mass 82.6 ± 6.3 kg, V˙O2max 60.7 ± 8.1 mL · kg–1 · min–1, peak power output 401.8 ± 31.4 W) completed all aspects of the study. The participants were nonsmokers and regular caffeine consumers (mean caffeine consumption 271 ± 29 5 mg/d). Seven participants were regular consumers of energy drinks (with 6 regularly drinking Red Bull), and 4 consistently used them before or during competition. This study was conducted in accordance with the procedures approved by the human research ethics committee of Griffith University, and all potential recruits provided written informed consent before research participation.
Preexperimental Protocol Each participant reported to the laboratory on 6 separate occasions. During the first visit, participants underwent an incremental test to exhaustion on an electronically braked cycle ergometer (Lode Instruments, Groningen, Netherlands) to establish their maximal oxygen uptake (V˙O2max) and peak power output. The V˙O2max test (previously described by Desbrow et al22) began with 5 minutes cycling at 100 W and increased by 50 W every 2.5 minutes until exhaustion. Participants were fitted with a mouthpiece to measure expired gases (O2 and CO2) through a calibrated metabolic measuring system (MedGraphics, St Paul, MN, USA). After the initial visit, participants returned to the laboratory on 2 separate occasions to complete familiarization sessions that simulated trial procedures with the exception of blood-sample collection. The primary aim of these familiarization sessions was to reduce the practice or learning effect, but they also allowed participants to become familiar with test equipment and procedures and to establish a self-selected warm-up that would be replicated throughout the trials.
Experimental Protocol After completion of the familiarization sessions, all participants completed 3 experimental trials that consisted of a TT lasting approximately 1 hour and were separated by at least 7 days. The order of the experimental trials was randomized by a person independent to the study using an incomplete Latin-square design. In the 24 hours preceding each trial, participants were required to abstain from strenuous exercise, alcohol, and all sources of caffeine. Each participant received a standardized prepackaged diet to follow for 24 hours before each trial, which aimed to provide 200 kJ/kg BM, including 7.5 g/kg BM of CHO, following the recommendations for dietary standardization in previous studies.23,24 There were no restrictions placed on participants with regard to water consumption. All trials were completed in a stable laboratory environment (19°C ± 2°C, ~55% relative humidity) at the same time of day. On the morning of the trial, participants reported to the laboratory after an overnight fast (commencing from 8 PM). Immediately on arrival approximately 5 mL of blood was collected via forearm venipuncture for plasma caffeine analysis to ensure compliance with caffeine abstinence. The treatment, which consisted of 9.4 mL/kg BM of energy drink (either Red Bull [Red Bull GmbH, Austria] or CHO-matched placebo) and capsules (either anhydrous caffeine [PCCA, USA] or placebo), was provided to participants immediately after the blood collection. Participants were then given a pretrial meal in the form of 1.5 g/kg BM of Powerbar, which in combination with the energy drink ensured that they ingested 42 kJ/kg BM with approximately 2 g/kg BM of CHO before the TT. Dietary compliance was confirmed via a checklist followed by a brief questionnaire on the level of gastric discomfort (if any) the participant experienced. Participants were then required to rest quietly for ~90 minutes. They completed their preselected warmup, during which time they were provided with ~3 mL/kg BM of commercial sports drink (Gatorade). This warm-up was followed by collection of another 5 mL of blood via forearm venipuncture, which occurred 90 minutes after treatment ingestion. The exercise protocol used was a TT lasting ~1 hour, as described by Jeukendrup et al,21 in which participants aimed to complete a set amount of work as quickly as possible. The amount of work participants were required to perform was the equivalent of 60 minutes cycling at 75% of individual peak power output (as calculated in the incremental test to exhaustion). Performance times, heart-rate (HR) values, and ratings of perceived exertion (RPE) (using the Borg scale) were recorded at every 10% of work completed, 95%, and 99%, as well as at immediate completion of each trial. HR values were obtained using an HR monitor (Polar Electro, Kempele, Finland). Participants were provided with 3 mL/kg BM of Gatorade at 30% and 60% of work completed. Immediately after completing each trial, participants were asked to quantify any gastric discomfort experienced (on a scale of 1–10), as well as any leg-muscle pain, using a category scale previously described.25,26 A final 5-mL blood sample was taken via forearm venipuncture exactly 5 minutes after completion of the TT, and participants were asked to complete a brief questionnaire regarding their perceived performance and which treatment they believed they had received. All collected blood samples were kept in a lithium heparin Vacutainer to prevent coagulation before centrifugation at 3200 rpm for 10 minutes at 4°C. The plasma was then stored at –84°C to await analysis. Determination of plasma caffeine was undertaken using reverse-phase high-performance liquid chromatography (HPLC) analysis. The concentration of caffeine was quantified through
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extrapolation from calibration curves generated on the day of analysis. The protocol for identification and quantification of caffeine was adapted from HPLC conditions previously reported,27 and the coefficients of variation were >5% for accuracy and repeatability. Analysis of plasma glucose concentrations was conducted using the COBAS Integra 400+ automated blood analyzer. The coefficient of variation with regard to glucose analysis was 0.4% at 4.5 mmol/L and 0.5% at 12.5 mmol/L.
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Supplementation Red Bull energy drink and the placebo were matched for energy (185 kJ/100 mL), CHO (11 g/100 mL), and volume (9.4m L/kg BM). The placebo employed for this trial was concentrated Gatorade powder (Fierce Berry) mixed with carbonated water (SodaStream). Treatments were administered in opaque bottles, and a small amount of pink food coloring was added to the Red Bull drink to mask the difference in color of the 2 drinks. Drinks were prepared in advance by an independent researcher so that both participants and investigators were unaware of the contents of each drink. Participants were informed they would be receiving either caffeine or an energy drink for each trial and were not given any information relating to the possible contents of the drinks, with the research team referring to them as only “energy drinks.” The same volume of beverage used for the initial trial was used for subsequent trials. The placebo capsule consisted of a similar volume of Metamucil. The presence of a placebo trial was only mentioned at the completion of the 3 trials before the final survey.
in comparison with placebo (Table 1). The mean TT times for the placebo, caffeine, and Red Bull trials indicate that ingestion of 3 mg/ kg BM caffeine resulted in an improvement of 120 ± 172 seconds (3.1%) while Red Bull ingestion improved performance by 109 ± 153 seconds (2.8%) (Table 1). Mean power output was increased in Red Bull and caffeine treatments versus placebo, which corresponds to the improvements in performance times in both trials. Eight of the eleven participants recorded their slowest times during the placebo trial.
HR, RPE, and Quadriceps Muscle Pain While there was a trend toward higher mean HR values and quadriceps muscle pain in caffeine and Red Bull trials (HR, caffeine vs placebo P = .068 and Red Bull vs placebo P = .086; leg pain, caffeine vs placebo P = .085 and Red Bull vs placebo P = .052) compared
Statistical Analysis All statistical data collected were analyzed using the statistical software package IBM SPSS statistics 19 (Chicago, IL). Time to completion and quadriceps muscle pain were analyzed using a 1-way repeated-measures analysis of variance (ANOVA), while plasma caffeine, lactate, and glucose, as well as HR and RPE, were analyzed using a 2-way repeated-measures ANOVA. Pairwise comparisons between caffeinated beverages and the placebo trial were performed, and where significant main effects were observed, post hoc analysis was undertaken (Fischer least significant difference). All data are reported as mean ± SD. Statistical significance was taken as P < .05.
Figure 1 — Plasma caffeine concentrations across all trials.
Table 1 Effect of Ingesting a Commercial Energy Drink Before a Simulated 40-km Cycling Time Trial Compared With Anhydrous Caffeine or a Placebo Control Total time (s)
Results
Mean power output (W)
Placebo
Red Bull
Caffeine
3877 ± 260
3768 ± 257*
3757 ± 278*
287 ± 31
300 ± 30*
295 ± 31*
Heart rate (beats/min)
Standardization
rest
79.6 ± 13.6
76.1 ± 14.8
78.9 ± 12.4
Good compliance with both dietary and exercise-related standardizations were achieved by participants in the 24 hours preceding each trial. The mean dietary intake reported was 199 ± 26 kJ/kg BM energy and 7.3 ± 0.7 g/kg BM CHO. Participants also reported no consumption of alcohol during this time in addition to no strenuous exercise for 18 hours before each trial. Analysis of the initial plasma caffeine samples revealed no detectable caffeine (Figure 1), indicating that all participants successfully abstained from caffeine in the 24 hours preceding each trial. The mean volume of beverage consumed 90 minutes before exercise was 776 ± 59 mL.
mean
168.1 ± 10.0
171.6 ± 9.7
171.4 ± 8.9
100% work completed
172.9 ± 11.4
176.4 ± 10.4
176.7 ± 9.5
mean
15.2 ± 1.2
15.7 ± 1.1
15.3 ± 1.0
100% work completed
17.6 ± 1.4
17.9 ± 1.5
17.8 ± 1.4
Quadriceps muscle pain postexercise (1–10)
4.4 ± 1.3
5.4 ± 1.9
5.4 ± 1.7
predrink
5.4 ± 1.0
5.1 ± 0.6
5.1 ± 0.8
Performance
preexercise
4.1 ± 1.7
4.7 ± 1.6
3.6 ± 0.8
Time to complete the TT was significantly improved after ingestion of both caffeine (P = .043) and Red Bull (P = .039) treatments
postexercise
6.4 ± 0.7
6.6 ± 1.6
6.9 ± 1.8
RPE (6–20)
Blood glucose (mmol/L)
*P < .05 vs placebo.
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with placebo conditions, these values failed to reach statistical significance. No significant difference in RPE was observed when caffeine-containing trials were compared with the placebo trial.
Gastric Discomfort Gastric discomfort with a rating of >5 out of 10 was experienced by 2 participants after Red Bull ingestion (in addition to the 1 participant who withdrew from the study). These participants described the symptoms as “sharp/stabbing” or “regurgitating” with some associated nausea. Despite these reports, the participants’ performance on the Red Bull trial was faster than during the caffeine trial. Only minor (≤3 out of 10) ratings of gastrointestinal discomfort were reported in other trials.
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Plasma Caffeine and Glucose Acute ingestion of both caffeine and Red Bull resulted in significant increases in plasma caffeine concentrations (P < .05). There was no significant difference (all values P > .05) detected between caffeine and Red Bull treatments either immediately before or after the trials. Blood glucose was not significantly different (all P > .05) between the 3 conditions (Table 1).
Blinding No participant reported certainty about all treatment being administered. Only 1 participant correctly determined the order of all treatments. Three participants correctly identified the trial in which they received Red Bull; however, only 1 participant was certain of this choice. Five participants believed they received Red Bull after being administered the alternative drink (3 during the placebo trial, 2 during caffeine trial). Eight participants thought they were given an alternative caffeinated energy drink (not Red Bull) during all 3 trials.
Discussion The aim of this study was to compare the effects of a commercially available energy drink with an equivalent dose of anhydrous caffeine (3 mg/kg BM) on endurance-cycling TT performance undertaken after exercise and dietary control. Consistent with our hypothesis, we found that both Red Bull and anhydrous caffeine enhanced TT performance compared with placebo in trained, familiarized, and fed participants. This suggests that the ergogenic effects associated with Red Bull consumption relate directly to the beverage’s caffeine content. The magnitude of performance improvements observed due to caffeine (3.1%) and Red Bull (2.8%) treatments are comparable to many,16–18 but not all,14 previous studies investigating the ergogenic effects of caffeine on cycle TT performance lasting ~60 minutes. Indeed, the mean performance improvement calculated after a systematic review of endurance studies using TT-type protocols indicated an improvement of 2.3% ± 3.2% when caffeine was ingested before exercise.4 The outcome from the recent study by Phillips et al14 somewhat contradict the findings from the current study. Phillips et al14 failed to demonstrate any performance improvement relative to a control when ingesting either an energy drink or a CHO- and caffeine-matched cola beverage before undertaking an endurance-cycling TT. The differing results may, in part, be explained by differences in the methods employed. The protocol by Phillips et al14 used a smaller (~2 mg/kg BM) absolute caffeine dose. Previous studies have suggested that the
ergogenic effects of caffeine increase as doses increase up to ~3 mg/ kg BM, with no further increase above this dose.17,28,29 In addition, the participants had, on average, lower aerobic capacity (52 vs 60 mL · kg–1 · min-1), and the use of drinks with clearly different flavor profiles denotes that expectancy effects cannot be entirely excluded. The studies do, however, concur that no performance differences are evident between the ingestion of an energy drink and that of a beverage with matching amounts of caffeine and CHO. Alongside CHO and caffeine, other (secondary) ingredients with the potential to influence performance in Red Bull include taurine, glucuronolactone, and B-complex vitamins. Limited research examining the effect of these secondary ingredients on mechanisms underpinning endurance performance and/or performance itself exists. Indeed, taurine, glucuronolactone, and B-complex vitamins do not appear to substantially alter aerobic metabolism when consumed as a combination30 or in isolation (ie, taurine only)31,32 (no investigations using isolated glucuronolactone or B-complex vitamins were identified). The current results suggest that secondary ingredients in energy drinks do not influence blood glucose, plasma caffeine, quadriceps muscle pain, HR, or RPE when compared with the same dose of pure caffeine delivered before an endurance task. Furthermore, when measured, any effect of the secondary ingredients on endurance-exercise performance appear small32 or absent (current study and that of Rutherford et al31). This suggests that trained individuals consuming caffeinated energy drinks in an attempt to improve endurance performance lasting ~1 hour receive minimal, if any, additional benefit from the other constituents contained in Red Bull.
Practical Application The volume of a caffeinated energy drink required to provide a 3-mg/kg BM dose of caffeine is substantial (~3 × 250-mL cans). It is important to note that a number of participants in the current study experienced severe stomach pains during the Red Bull trials, which were not observed when the same volume of fluid and amount of CHO was consumed in the caffeine and placebo trials. The potential for specific ingredients in energy drinks to cause gastrointestinal discomfort during exercise warrants further consideration. Clearly, using energy drinks as the mode of caffeine delivery for performance enhancement will require consideration of the volume needed, palatability, and event characteristics (eg, duration and/or mode of exercise), which may all affect potential gastrointestinal tolerance.
Conclusions This study demonstrated that a moderate dose of caffeine consumed via Red Bull energy drink or anhydrous caffeine enhance endurance-cycling TT performance by a similar magnitude. The ergogenic effect of the energy drink is therefore most likely the result of its caffeine content, with the other ingredients offering no further benefit. Acknowledgments Funding for this investigation was provided from internal Griffith University support.
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