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Study Title and Description

Caffeine improves physical and cognitive performance during exhaustive exercise.



Key Questions Addressed
1 For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on cardiovascular outcomes?
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Primary Publication Information
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TitleData
Title Caffeine improves physical and cognitive performance during exhaustive exercise.
Author E Hogervorst,S Bandelow,J Schmitt,R Jentjens,M Oliveira,J Allgrove,T Carter,M Gleeson,
Country
Year 2008
Numbers

Secondary Publication Information
There are currently no secondary publications defined for this study.


Extraction Form: Cardiovascular Design
Design Details
Question... Follow Up Answer Follow-up Answer
What outcome is being evaluated in this paper? Cardiovascular
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What is the objective of the study (as reported by the authors)? To examine the effects of ingesting a performance bar, containing caffeine, before and during cycling exercise on physical and cognitive performance.
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Provide a general description of the methods as reported by the authors. Information should be extracted based on relevance to the SR (i.e., caffeine related methods) Participants: Male-only subjects were recruited through personal contacts, advertisements in local sports clubs and the student pool of the University of Loughborough (UK), and/or by word of mouth. Subjects were enrolled after having fulfilled all inclusion criteria and presenting none of the exclusion criteria (determined by both questionnaire and interview). All participants were fully informed about the rationale for the study and of all experimental procedures to be undertaken. Participants could be included if they were healthy, endurance-trained male volunteers, had cycling as one of their main sports, preferably with some competitive practice, and were moderate habitual caffeine users. Because of time constraints, we had to include four participants who were caffeine-naive but were subsequently asked to increase their daily caffeine intake before the study (which was reflected by their increased resting salivary caffeine concentrations during the study). Two participants reported an equivalent intake of more than six cups of coffee per day, but all others consumed the equivalent of less than four cups of coffee per day. Participants were between 18 and 35 yr of age. Subjects representing one or more of the following criteria were excluded from participation: smoking or use of any (in particular, psychoactive) medication that could interfere with test performance or use of illicit drugs; experienced or had a history of cardiac, hepatic, renal, pulmonary, neurologic, gastrointestinal, hematological, or psychiatric illness or with any sensory or motor deficits that could be expected to affect test performance; and objected to the prescription of diet (recall of diet, alcohol abstention), exercise, and resting regimens or those who will not be expected to comply with treatment. Twenty-four healthy trained men [age, 23 +/- 5 years] were included in the present study. Subjects were assigned to the treatment groups in a double-blind, placebo-controlled, randomized, cross-over, single-center, clinical trial design. All participants completed five exercise bouts: two preliminary trials (VO2max determination and habituation trial) and three main trials. All trials were separated by at least 1 wk. Treatment composition: The two types of performance "energy" bars used in this study were commercially available coconut-flavored PowerBar Performance bars and consisted of protein (5.4 g), carbohydrate (44.9 g), fat (3.2 g), fiber (4.0 g), sodium (0.6 g), and vitamins and minerals in amounts intended for nutritional support of athletes. The two bars were a noncaffeine (CHO) and a caffeine-containing (CAF) version. The latter (ActiCaf bar) contained 100 mg of slow-release caffeine. The placebo beverage (BEV) consisted of artificially sweetened and flavored water (Vittel Raspberry flavor) and was not intended to provide energy or nutritional ingredients. Study design: Participants exercised under three different conditions: BEV trial, CAF trial, or CHO trial. The order in which each participant undertook each condition (BEV, CAF, or CHO trial) was randomized and counterbalanced, where subjects were randomly assigned to one of the six sequences in a balanced way (CAF CHO BEV, CHO BEV CAF, BEV CAF CHO, CAF BEV CHO, BEV CHO CAF, and CHO CAF BEV). Randomization was performed by TrialBalance (Nestle´ program for randomization) in blocks to ensure balance (each treatment was applied equal times at each period). No form of stratification was applied. Blinding: Four different codes were created for the performance bars (Y, Z, X, and W, where CAF = Y and W, and CHO = Z and X ), and subjects and investigators were blinded about the content of each bar until after completion of the study. Participants were told that any of the beverages/bars could or could not contain caffeine. However, the beverage was not blinded for the investigators who were responsible for buying and measuring quantities before administrating the blinded drinks to the volunteers. Both subjects and investigators were not allowed to discuss the experimental treatments in any format during the trials. At the end of each trial, participants completed a questionnaire to try to guess which treatment they had been given (e.g., caffeine bar, noncaffeine bar, and caffeine or noncaffeine beverage) to check adequacy of blinding procedures. Protocol before the treatment trials: A Polar heart rate (HR) monitor (Vantage NV; Polar, Kempele, Finland) was used for continuous recording of the HR. Standard measures of height and body mass were also performed during this visit. Protocols during treatment trials: Participants then consumed their first experimental product (performance bar or beverage) within 5 min and performed 150 min of exercise at 60% V˙ O2max immediately after the consumption of the product. Further experimental supplementation of either CAF, CHO, or 300 mL of BEV was given at 55 and 115 min. In addition, 200 mL of water was consumed at the onset and every 20 min during the exercise bout for all trials. During exercise, the following measurements (as illustrated in Fig. 1) were taken: A caffeine side effect questionnaire and the cognitive performance tasks (Stroop Color–Word and RVIP tests) were administered at 70 and 140 min. The caffeine side effect questionnaire was developed on the basis of common and known side effects after administration, withdrawal, and overdosing of caffeine, which were categorized as nervous system, gastrointestinal, pulmonary, and cardiovascular effects. The questionnaire was computerized and presented before each cognitive test trial. The total number of side effects per trial was reported. Rating of perceived exertion (RPE) was assessed during exercise every 20 min using a paper version of the 0–20 Borg scale (2). Earlobe blood drawing (for glucose analysis as described above) and saliva sampling (before cognitive test sessions) were carried out at 65 and 125 min. Oxygen uptake, carbon dioxide production, and respiratory exchange ratio (RER; during exercise at 30, 90, and 115 min) were assessed using a Douglas Bag collection system, Servomex gas analyzer, and Harvard dry gas meter, and HR (every 10 min) was monitored using a Polar HR monitor (Vantage NV; Polar). At the end of the 150-min exercise, subjects were given a 5-min break, immediately followed by a time to exhaustion trial at 75% V˙ O2max . Participants were instructed to maintain a pedal cadence of more than 50 rpm while cycling to remain seated at all time and to attempt to cycle for as long as possible. However, no external encouragement was given during the trial. No music was played and no clues about elapsed time, power output, and HR were given during the ride to exhaustion. HR was recorded unobtrusively every 5 min during the ride to exhaustion. Immediately after completion of the exercise to exhaustion trial, a saliva sample and an earlobe blood sample (for glucose analysis) were collected.
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How many outcome-specific endpoints are evaluated? 1
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What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Heart rate
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List additional health endpoints (separately). 2
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List additional health endpoints (separately).3
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List additional health endpoints (separately).4
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List additional health endpoints (separately).5
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List additional health endpoints (separately).6
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Clinical, physiological, other Physiological
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What is the study design? Controlled Trial
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Randomized or Non-Randomized? RCT
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What were the diagnostics or methods used to measure the outcome? Objective
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Optional: Name of Method or short description A Polar heart rate (HR) monitor (Vantage NV; Polar, Kempele, Finland) was used for continuous recording of the heart rate.
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Caffeine (general) Caffeine (general)
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Coffee, Chocolate, energy drink, gum, medicine/supplement, soda, tea, other?
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Measured or self reported? Measured
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Children, adolescents, adults, or pregnant included? Adults
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What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) Each subject received each treatment. Treatments were: caffeine-containing performance bar, non-caffeinated performance bar, or 300 mL of placebo beverage.
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What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models.  Copy from methods) Subjects representing one or more of the following criteria were excluded from participation: smoking or use of any (in particular, psychoactive) medication that could interfere with test performance or use of illicit drugs; experienced or had a history of cardiac, hepatic, renal, pulmonary, neurologic, gastrointestinal, hematological, or psychiatric illness or with any sensory or motor deficits that could be expected to affect test performance; and objected to the prescription of diet (recall of diet, alcohol abstention), exercise, and resting regimens or those who will not be expected to comply with treatment. Overall, treatment effects (including treatments BEV, CAF, and CHO) were analyzed via repeated-measures ANOVA that included the main effect of treatment, time, visit day, and treatment x time interactions. If a significant treatment x time interaction was found, the responses at 70, 140, and 180 min were analyzed using mixed-effects models. These models contained fixed main effects of treatment, fixed main effect for mean scores at time 0 (to adjust for baseline speed), and a fixed main effect for visit day (to account for learning between visits). The nlme package was used to build linear mixed-effect (lme) models for the normally distributed RT data. The lme4 package was used to build the same models for binomial data such as the proportion of correct answers, which were modeled via the binomial distribution. The resulting adjusted P values for the contrasts CAF–CHO, BEV–CAF, and BEV–CHO are listed in Figures 2–4 as CCO, CAF, and CHO, respectively. Significance codes of the post hoc comparisons (adjusted for three comparisons at each time point) are as follows: *P<0.05, **P<0.01, and ***P<0.001. For these post hoc tests, the correlations between BEV, CHO, and CAF samples were found to be approximately 0.5; hence, the adjusted Bonferroni-corrected alpha level for three comparisons used was 0.03. To compare the physiological and other responses (HR, maximum HR, RPE, blood glucose concentration, time to exhaustion, sweat loss, and % V˙ O2max ) between the three different treatments (CAF, CHO, and BEV), repeated-measures general linear models were used. Post hoc analyses were carried out, where appropriate, using Bonferroni corrections. All statistical analyses were carried out blinded to treatment by the onsite investigators (caffeine in saliva was analyzed last).
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What conflicts of interest were reported? The authors did not mention conflicts of interest.
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Refid 18799996
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What were the sources of funding? This study was fully sponsored by Nestle, Switzerland.
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Results & Comparisons

No Results found.