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Study Title and Description

Neuromuscular responses to incremental caffeine doses: performance and side effects.



Key Questions Addressed
1 For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on behavior*?
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Primary Publication Information
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TitleData
Title Neuromuscular responses to incremental caffeine doses: performance and side effects.
Author JG Pallarés,VE Fernández-Elías,JF Ortega,G Muñoz,J Muñoz-Guerra,R Mora-Rodríguez,
Country
Year 2013
Numbers

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


Extraction Form: Behavior - Design Details - INCLUDED Studies
Arms
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Design Details
Question... Follow Up Answer Follow-up Answer
Refid 23669879
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What outcome is being evaluated in this paper? Behavior
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What is the objective of the study (as reported by the authors)? The purpose of this study was to determine the oral dose of caffeine needed to increase muscle force and power output during all-out single multijoint movements.
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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) Thirteen resistance-trained men underwent a battery of muscle strength and power tests in a randomized, double-blind, crossover design, under four different conditions: (a) placebo ingestion (PLAC) or with caffeine ingestion at doses of (b) 3 mg · kg(-1) body weight (CAFF 3mg), (c) 6 mg · kg(-1) (CAFF 6mg), and (d) 9 mg · kg(-1) (CAFF 9mg). The muscle strength and power tests consisted in the measurement of bar displacement velocity and muscle power output during free-weight full-squat (SQ) and bench press (BP) exercises against four incremental loads (25%, 50%, 75%, and 90% one-repetition maximum [1RM]). Cycling peak power output was measured using a 4-s inertial load test. Caffeine side effects were evaluated at the end of each trial and 24 h later. Side effects evaluation. Immediately after each neuromuscular test battery (QUEST + 0 h) and 24 h later (QUEST + 24 h), participants answered a questionnaire. The QUEST + 0 h was designed to evaluate the physical fatigue, the perceived performance, and the side effects (e.g., urine output, gastrointestinal problems, tachycardia, or headache) felt by the participants during the neuromuscular test battery. QUEST + 24 h was designed to evaluate physical fatigue and side effects (e.g., sleep quality, gastrointestinal problems, tachycardia, muscle soreness, or headache) perceived by participants during the 24 h after the caffeine dose was ingested. These surveys included eight items on a yes/no scale and were based on previous publications about side effects derived from the ingestion of caffeine (8,11). Statistical analysis. The Shapiro–Wilk test was used to assess normal distribution of data. Reported side effects in the questionnaires were not normally distributed, and a nonparametric statistical technique was used.
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How many outcome-specific endpoints are evaluated? 3
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What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Anxiety
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List additional health endpoints (separately).
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List additional health endpoints (separately)
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Notes sleep was measured as reported insomnia
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Clinical Clinical
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Physiological Physiological
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Other
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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? Subjective
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Optional: Name of Method or short description Side effects evaluation. Immediately after each neuromuscular test battery (QUEST + 0 h) and 24 h later (QUEST + 24 h), participants answered a questionnaire. The QUEST + 0 h was designed to evaluate the physical fatigue, the perceived performance, and the side effects (e.g., urine output, gastrointestinal problems, tachycardia, or headache) felt by the participants during the neuromuscular test battery. QUEST + 24 h was designed to evaluate physical fatigue and side effects (e.g., sleep quality, gastrointestinal problems, tachycardia, muscle soreness, or headache) perceived by participants during the 24 h after the caffeine dose was ingested. These surveys included eight items on a yes/no scale and were based on previous publications about side effects derived from the ingestion of caffeine (8,11).
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Caffeine (general) Caffeine (general)
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Coffee
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Chocolate
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Energy drinks
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Gum
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Medicine/Supplement
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Soda
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Tea
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Measured Measured
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Self-report
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Children
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Adolescents
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Adults Adults
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Pregnant Women
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What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) placebo (0 mg caffeine) vs (3, 6, or 9 mg/kg caffeine)
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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) N/A
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Provide a general description of results (as reported by the authors). Finally, the CAFF9mg trial produced a drastic increase in the reported frequency of side effects (Table 1). The following morning of each experimental trial (QUEST + 24 h), very few participants (8%) reported that PLAC treatment produced residual side effects such as muscle soreness, increase in the estimates of urine output, and gastrointestinal problems. The CAFF3mg trial produced very similar side effects to PLAC, with an additional 8% of participants reporting a headache. The CAFF6mg trial tended to increase the frequency of muscle soreness and headaches and the estimates of urine output in comparison with the PLAC and CAFF3mg treatments, although still with a frequency lower than 31% of the subjects. In addition, CAFF6mg produced symptoms of increased vigor and sleep problems, although with a very low incidence (8%). Finally, CAFF9mg increased the frequency of all adverse side effects, with a frequency of appearance from 23% to 54%. Of note, 23% of participants reported tachycardia and anxiety or nervousness, 38% with gastrointestinal problems, and 54% with insomnia or sleep disturbances (Table 1).
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Did the authors perform a dose-response analysis (or trend/related analysis)? No
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What were the authors's observations re: trend analysis?
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What were the author's conclusions? One of the findings of the present study was that the presence of negative side effects increased markedly with the 9-mg/kg caffeine dose (Table 1). In the present study, we found gastrointestinal problems, headaches, and insomnia appearing with doses at or higher than 6 mg/kg (Table 1).
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What were the sources of funding? No funding was received for this work.
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What conflicts of interest were reported? The authors report no conflicts of interest.
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Does the exposure (dose) need to be standardized to the SR? Multiple metrics
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Provide calculations/conversions for the exposure based on the decision tree in the guide (for all endpoints/exposure levels of interest). Average body weight of participant = 76.5 kg 3 mg/kg = 230 mg caffeine 6 mg/kg = 459 mg caffeine 9 mg/kg = 689 mg caffeine
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List all the endpoint(s) followed by the dose (mg) which will be used in comparison to Nawrot.  Characterize value as LOAEL/NOAEL, etc. if possible.  anxiety LOAEL = 689 mg caffeine/day; NOAEL = 230 mg/day caffeine headaches LOAEL = 459 mg caffeine/day; NOAEL = 230 mg/day caffeine insomnia LOAEL = 459 mg caffeine/day; NOAEL = 230 mg/day caffeine
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Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot. effects seen at levels higher than Nawrot
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What is the importance of the study with respect to the adverseness of the outcome? Important
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Results & Comparisons

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Adverse Events
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