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Study Title and Description

Physiological and cognitive responses to caffeine during repeated, high-intensity 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 Physiological and cognitive responses to caffeine during repeated, high-intensity exercise.
Author MJ Crowe,AS Leicht,WL Spinks,
Country
Year 2006
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)? This study investigated the effects of a single dose of caffeine on cognitive, blood, and performance parameters during maximal, repeated, anaerobic exercise.
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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) Subjects Seventeen healthy, non-smoking subjects (12 male, 5 female; mean +/- standard deviation age, 21.1 +/- 3.0 y; height, 177.5 +/- 8.9 cm; weight 73.3 +/- 10.5 kg) agreed to participate in this study. The subjects were non-specifically trained with the majority regularly participating in team sports including soccer, rugby league, rugby union, netball, and basketball. Four of the subjects (3 male, 1 female) were light-to-moderate habitual caffeine consumers (approximately 80 to 200 mg/d) while the remaining subjects were habitual non-consumers. All subjects underwent medical prescreening and were questioned for possible reactions to caffeine before being included in the study. Experimental Protocol A repeated measures design was employed where all subjects completed three testing sessions at the same time of day, 7 d apart. Each subject was randomly allocated to one of three treatments for each testing session. The treatments included control, where there was no intervention, placebo, and caffeine. The caffeine and placebo treatments were performed in a double-blind manner and involved either consumption of caffeine (6 mg/kg 1,3,7-trimethylxanthine; Sigma-Aldrich, Sydney, Australia) dissolved in 400 mL of caffeine-free diet cola or a placebo (400 mL of caffeine-free diet cola). All subjects were familiarized with the experimental protocol by completing the whole exercise protocol approximately 5 to 7 d prior to commencement of the first testing session. The subjects were requested to abstain from caffeine for 48 h prior to each testing session and to maintain a consistent exercise and diet regime for the duration of the study. All subjects abstained from moderate to intense exercise in the 24 h prior to exercise testing. A 4-d diet diary was analyzed using FoodWise dietary analysis software (2001; McGraw-Hill Companies, Inc., New York). The same person analyzed all diet data to maintain consistency. An abstinence from alcohol in the 24 h prior to testing and all other dietary supplements for the duration of the study was also verified from the diet diaries. At each of the three testing sessions the subjects completed assessments before consumption of caffeine or placebo (baseline), 72 to 90 min after consumption of caffeine or placebo (post-ingestion) and immediately after exercise (post-exercise). Ninety minutes elapsed between consumption of the caffeine and commencement of the exercise test. Assessments were made of cognitive and blood parameters as well as exercise performance variables. Exercise Test The exercise test was preceded by a 5 min warm-up on an air-braked cycle ergometer (Repco Ergo, Repco Cycle Co., Huntingdale, Australia) at 50 to 100 W. The subjects then commenced a 2 x 60 s maximal cycle test separated by 3 min passive seated recovery on the ergometer. Peak HR (HRpeak; beats/min) was recorded during each 60 s bout using a telemetric heart rate monitor (Polar Electro OY, Kempele, Finland). Blood testing Venipuncture blood was taken from a medial antecubital vein at baseline, in the 2 to 3 min prior to warm-up, and immediately upon cessation of the last exercise bout. Plasma caffeine concentrations were assessed using Syva Emit kits (Hoechst Diagnostics, Germany) and a Cobas Fara spectrophotometer (Roche, Castle Hill, Australia). Plasma catecholamines were analyzed via reverse phase isocratic high performance liquid chromatography (HPLC) as described by Holmes et al. using a HPLC separation module (2695 Waters Separation Module; Waters Corporation, Milford, MA) and Coulochem detector (model 5200 Coulochem detector; ESA, Inc., Chelmsford, MA). Statistical Analysis All data were analyzed using SPSS for Windows software (version 11; SPSS, Inc., Chicago, IL). A two-way (treatment x time), repeated measures ANOVA was used to analyze the data with a 3 x 2 design used for reaction time, number recall, and plasma caffeine and a 3 x 3 design used for blood glucose and lactate, plasma epinephrine, and norepinephrine. The Greenhouse-Geiser correction was used where sphericity was violated. Post hoc analysis was completed using the Tukey HSD test. Statistical power is reported for each significant finding. Alpha was set to 0.05 and all data are presented as means +/- standard deviation.
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How many outcome-specific endpoints are evaluated? 2
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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 Plasma catecholamines (epinephrine and norepinephrine)
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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 Heart rate was recorded using a telemetric heart rate monitor (Polar Electro OY, Kempele, Finland). Plasma catecholamines were analyzed via reverse phase isocratic high performance liquid chromatography (HPLC).
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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.) Placebo and unexposed controls
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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) None
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What conflicts of interest were reported? No information provided
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Refid 17240784
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What were the sources of funding? No information provided
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Results & Comparisons

No Results found.