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Study Title and Description

Caffeine ingestion does not alter performance during a 100-km cycling time-trial 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 Caffeine ingestion does not alter performance during a 100-km cycling time-trial performance.
Author AM Hunter,A St Clair Gibson,M Collins,M Lambert,TD Noakes,
Country
Year 2002
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)? In this study, we evaluated the effects of caffeine ingestion on performance during a 100-km cycling time trial, which included high intensity epochs (HIE).
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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 Fifteen competitive, endurance-trained male cyclists volunteered for this study, with 8 completing the full trial. Seven of the original 15 subjects were excluded—2 because they were unable to achieve the required cycling speed and 5 because they found the trial "too arduous". The mean age and weight of the 8 subjects who completed the trial were 23.5 ± 6.7 years and 66.8 ± 6.2 kg, respectively. Experimental Procedure Each subject reported to the laboratory on four separate occasions. During the first visit, subjects familiarized themselves with the equipment and laboratory conditions; thereafter, they completed a familiarization 100-km cycling time trial (TT), during which they ingested their own chosen fluid replacement solutions ad libitum. All other conditions were identical except that subjects were also not given tablets, nor were they forced to drink at specific, regular intervals during the familiarization trial. Subjects completed a TT during each of the next three visits. Each visit was separated by a minimum of 6 and a maximum of 8 days. For each subject, the 3 TTs were conducted at the same time of day in the environmental chamber at an ambient temperature of 27 °C, a relative humidity (Rh) of 50 ± 0.9%, and a wind velocity (v) of 15 ± 0.4 km · h–1. The trials were randomized, and subjects were blinded to the nature of each trial. The subjects were requested to perform the same type of training for the duration of the trial and to refrain from heavy physical exercise on the day before a TT. Subjects completed a nutritional information sheet on which they recorded their food and fluid intake for 3 days preceding the TT. Subjects were instructed to avoid any caffeine containing products for 48 hours before each time trial. They were specifically asked to abstain from all the obvious sources of caffeine including coffee, tea, cola drinks, chocolate, and over-the-counter caffeine containing pharmaceuticals. They were requested to report any deviations from these instructions. The day prior to the trial, the subjects followed a prescribed diet. They were instructed to repeat the same dietary regimen before each subsequent trial. In addition, before each experiment, subjects were issued a standardized breakfast, which was consumed 3 hours prior to commencing the TT. Only subjects who followed the standardized dietary and training protocol were allowed to continue with the study. After reporting to the laboratory, the subjects ingested gelatin capsules containing placebo (white flour) with 150 ml of either a sports electrolyte solution containing a sweetener (1.7% carbohydrate; Pl) or the same solution with 7% carbohydrate without sweetener (Cho), or gelatin capsules containing caffeine (6 mg/kg) with the 7% carbohydrate solution (Caf). Because a considerable amount of caffeine is excreted through sweat during endurance exercise, and as exercise increases the expression of cytochrome P450 1A2 (45), decreasing peak plasma caffeine levels and half-life, it was considered necessary that subjects also ingest a maintenance dose of 0.33 mg/kg BW of caffeine every 15 min during the Caf trial. This maintenance dose was calculated to ensure that the overall caffeine dosage did not exceed 9 mg/kg (a bolus amount of 6 mg/kg BW caffeine followed by a maintenance dose of 3 mg/kg BW over the TT of approximately 2.5 hours). During the two other trials (Pl and Cho), flour-containing gelatin tablets were ingested every 15 min. One hour after ingesting the initial solution and capsules, a resting blood sample was taken and urine sample collected, and body weight was measured on a precision scale (Soehnle, Germany). After a standardized 5-min warm up of easy cycling, subjects commenced with the 100-km time trial. Every 15 min the subjects were given either the caffeine or placebo capsules together with 150 ml of either the carbohydrate or placebo drinks. The time trial included a series of HIE, during which subjects were requested to ride "as fast as possible". There were five 1-km HIE after 10, 32, 52, 72, and 99 km, as well as four 4-km HIE after 20, 40, 60, and 80 km. Subjects were instructed to complete the total distance in "the fastest time possible", taking into consideration the HIE that were included. Throughout each trial, heart rate was recorded using a Sport Tester monitor (Polar Electro, Kempele, Finland). Heart rate was recorded at each 500-m split of both the 1-km and 4-km HIE. Upon completion of the TT, subjects had their bodyweight recorded, urine sample collected, and a final blood sample drawn. Finally, subjects were asked whether they could determine which solution, caffeine or placebo, they had received and to describe the basis on which they made that choice. Statistical Analysis Data are presented as means and standard deviations. A two-way ANOVA for repeated measures was used to evaluate statistical significance of all the variables measured. A Scheffe’s post hoc test was used to reduce the possibility of incurring a type I error and automated checks for spericity were computed by the Statistica program. The data was analyzed by a 3 (condition) x 5 (time) and 3 (condition) x 4 (time) ANOVA for the 1-km and the 4-km HIE, respectively. Significance was accepted at p ≤ .05.
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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 Heart rate was recorded using a Sport Tester monitor (Polar Electro, Kempele, 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.) Subject 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) None
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What conflicts of interest were reported? No information provided
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Refid 12500987
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What were the sources of funding? No information provided
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Results & Comparisons

No Results found.