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Study Title and Description

Effects of caffeine on repetitions to failure and ratings of perceived exertion during resistance training.



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 Effects of caffeine on repetitions to failure and ratings of perceived exertion during resistance training.
Author JM Green,PJ Wickwire,JR McLester,S Gendle,G Hudson,RC Pritchett,CM Laurent,
Country
Year 2007
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 examined effects of caffeine (Ca) on number repetitions (reps), ratings of perceived exertion (RPE), and peak heart rate (PHR) during resistance-training exercise with reps performed to volitional failure.
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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: Physically active men (n = 13) and women (n = 4) who had been strength training for a minimum of 8 weeks served as participants. Before data collection, they signed a written informed consent outlining study requirements. All procedures were approved by the local institutional review board for protection of human subjects. Each participant arrived at the testing site with instructions to be well hydrated and at minimum 3 hours postprandial. Participants were also instructed to avoid alcohol and caffeine (excluding treatment) for at least 24 hours before testing. Performance trials: After exercise-specific 10-RM (repetition maximums) had been determined, subjects were supplied with capsules containing either treatment (caffeine) or placebo in amounts equaling 6 mg/kg body weight. Participants consumed the substance 1 hour before reporting for testing. Caffeine (Ca) and placebo (Pl) trials were counterbalanced and administered in a double-blind manner. On reporting, subjects donned a Polar heart-rate monitor at the level of the sternum and then completed a short stretching routine. They then completed a warm-up set of BP or LP at what they considered a "light" intensity for no more than 12 repetitions. After warm-up subjects completed 3 sets of either BP or LP followed by 3 sets of the alternate exercise (order of exercises counterbalanced). Sets were separated by 3 minutes passive recovery, with 5 minutes between the 2 exercises. Successful repetitions and peak heart rate (PHR) were recorded for each set. Subjects also provided an RPE (specific to active musculature) according to the omni RPE scale within the 10 to 15 seconds immediately after each set. Verbal encouragement was provided during testing. On completion of the first performance-testing session, participants were provided with capsules containing the alternate treatment. Performance session 2 was completed with a minimum of 2 days rest after the first session but within 7 days.
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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) Peak 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 Polar heart-rate monitor at the level of the sternum
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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 vs. 6 mg/kg caffeine administration.
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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) Ca and Pl treatments were compared using a 2 (trial) x 3 (set) repeated-measures ANOVA for each variable (repetitions, RPE, and PHR), with the Tukey honestly significant difference used for post hoc analysis when needed. Coefficients of variation were used as measures of reliability. Estimates of effect size (partial eta squared; η) were computed to illustrate the strength of association between the treatment (Ca) and the observed changes. Questionnaire responses were compared between Ca and Pl using a paired t-test for each variable.
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What conflicts of interest were reported? Not mentioned.
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Refid 19168925
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What were the sources of funding? Not mentioned.
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Results & Comparisons

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