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Study Title and Description

Pharmacological and psychological effects of caffeine ingestion in 40-km cycling performance.



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 Pharmacological and psychological effects of caffeine ingestion in 40-km cycling performance.
Author AJ Foad,CJ Beedie,DA Coleman,
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 explore the psychological and pharmacological effects of caffeine in laboratory cycling 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) Study design: The aim of the study was to use a 2 (drug: caffeine/no caffeine) x 2 (belief: caffeine/no caffeine) within-subjects repeated-measures design to quantify the placebo and pharmacological effects of caffeine on 40-km cycling performance. This approach required the subjects to be deceived about the substance they had ingested in both the informed caffeine/received placebo (i.e., placebo) and informed no treatment/received caffeine (i.e., antiplacebo) conditions. Subjects: Subjects were 14 male road cyclists who were competing regularly at the time of the study. To ensure familiarity with the effects of caffeine and to control for individual differences in reactivity to caffeine from caffeine habitation, only moderate caffeine users (ingesting approximately 300 mg/day) were included in the study. Performance measure: Average power during a self-paced 40-km time trial was employed as the performance measure. Equipment: Heart rate was recorded every second during the test, using a portable heart rate monitor (Polar Vantage, Finland). Belief manipulation: Before the performance trials, and with the aim of catalyzing or reinforcing beliefs about caffeine, subjects were given a 90-min oral presentation and provided with literature reviewing both the findings of published research into caffeine and cycling performance, and detailing anecdotal evidence relating to the use of caffeine among elite cyclists. The efficacy of this manipulation of beliefs was supported by data collected in poststudy interviews. Substance administration: The antiplacebo condition—that is, informed no treatment/received caffeine—presented a significant procedural challenge, specifically, the requirement that an active substance be administered without the subject’s awareness. Before data collection, extensive pilot work with a different group of subjects was carried out to assess a variety of methods for the administration of caffeine in this manner. The most effective method, and that chosen for the present study, was to require subjects to consume 200 mL of chilled saline at the start of the warm-up, ostensibly to aid voluntary hydration and to maintain electrolyte balance during the time trials. The caffeine dose (5 mg/kg caffeine anhydrous; Gee Lawson, UK) was thus administered to subjects in chilled saline, and at no point during the study was caffeine administered via capsule. Thus, in the antiplacebo condition, before which subjects were explicitly informed that they were receiving no treatment, no capsule was administered, whereas in the caffeine condition, subjects were administered a placebo capsule (200 mg of cornflour, Sainsbury’s, UK, in a gelatin capsule) purporting to contain the caffeine to maintain the belief that the substance was being administered in this manner. An association between saline and a bitter taste was encouraged through administration of caffeine in saline in the caffeine condition, and this was reinforced in the subsequent antiplacebo condition. In placebo (i.e., informed caffeine/received placebo), no treatment (i.e., informed no treatment/received no treatment), and baseline conditions, pure saline was administered. Thus, the order of experimental conditions—caffeine, antiplacebo, placebo, and no treatment—was set to minimize changes in the taste of the saline. Counterbalancing of experimental conditions was, thus, not possible, because switching between conditions and, thus, between the pure and caffeinated saline, might produce such divergent gustatory cues as to potentially alert subjects to their treatment assignment. Experimental protocols: During a period of 14 wk, subjects performed 14 x 40-km time trials, each preceded by a standardized, progressive 20-min warm-up. Ratings of perceived exertion were not used, because these may have drawn the subjects’ attention to sensory and perceptual cues during performance, thereby increasing the risk of unblinding. No encouragement was given to subjects during the trials, and all performance feedback was reserved until the end of the study. Subjects were instructed to abstain from all caffeine-containing foods and beverages for 24 h before testing, to control for possible effects of caffeine already consumed, and they were asked not to use any other potentially ergogenic substances such as creatine monohydrate, sodium bicarbonate, and glycerol during the course of the study. Before baseline trials, subjects were informed, ‘‘Today you are performing a baseline trial.’’ Before informed caffeine/received caffeine and informed caffeine/received placebo trials, subjects were instructed, ‘‘Today you will be given caffeine,’’ and before informed no treatment/received caffeine and informed no treatment/received no treatment, subjects were instructed, ‘‘Today you are receiving no treatment’’ (note that received placebo refers to a placebo intervention—that is, the administration of a capsule containing an inert substance—whereas receive no treatment describes a condition in which no intervention is administered). (Note that belief in caffeine ingestion refers to both conditions in which subjects were informed that they had ingested caffeine—that is, the placebo condition and the caffeine condition.)
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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? NCT
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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 every second during the test, using a portable heart rate monitor (Polar Vantage, Finland).
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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.) Individuals served as their own 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) ANOVA was used to estimate main effects and interactions for mean values of power, heart rate, blood lactate, and maximal oxygen uptake.
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What conflicts of interest were reported? Conflicts of interested not mentioned by the authors.
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Refid 18091009
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What were the sources of funding? Funding not mentioned by the authors.
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Results & Comparisons

No Results found.