Study Title and Description
The use of energy drinks in sport: perceived ergogenicity and side effects in male and female athletes.
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*?|
Primary Publication Information
|Title||The use of energy drinks in sport: perceived ergogenicity and side effects in male and female athletes.|
|Author||JJ Salinero,B Lara,J Abian-Vicen,C Gonzalez-Millán,F Areces,C Gallo-Salazar,D Ruiz-Vicente,J Del Coso,|
Secondary Publication Information
There are currently no secondary publications defined for this study.
Extraction Form: Behavior - Design Details - INCLUDED Studies
No arms have been defined in this extraction form.
|Question... Follow Up||Answer||Follow-up Answer|
|What outcome is being evaluated in this paper?||Behavior|
|What is the objective of the study (as reported by the authors)?||The aim of the present study was to assess psycho-physiological changes and the prevalence of side effects resulting from the ingestion of 3 mg caffeine/kg body mass in the form of an energy drink.|
|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)||A total of ninety-eight athletes from seven different sport disciplines (rugby, volleyball, tennis, badminton, swimming, soccer and hockey) volunteered to participate in the study (Table 1). All the participants were especially recruited because they were light caffeine consumers (60 mg/d, approximately 1 cup of coffee). Participants were non-smokers and were not under medical treatment during the study period. Of these participants, eight did not complete all the required experimental protocols and their results were excluded from the statistical analysis. Thus, the study sample was composed of ninety participants (fifty-three male, thirty-seven female). We performed a priori statistical power analysis based on a previous study with the same caffeinated energy drink(20). To obtain significant differences between the ingestion of a caffeinated energy drink v. a placebo drink with an 80%of statistical power and with an alpha value of 1·96 (95% of confidence), we required a sample size of seventy-four participants to detect changes in nervousness or gastrointestinal side effects. Experimental design A double-blind and placebo-controlled experimental design was used for the present study. Each participant took part in two different experimental trials under the same experimental conditions and standardisations. The order of the experimental trials (e.g. caffeinated energy drink or placebo beverage) was randomised for each participant. To control for the order effects, the order of the experimental trials was counterbalanced and forty-five participants performed caffeinated energy drink and placebo beverage order while the remaining forty-five participants performed the placebo beverage and caffeinated energy drink order. To comply with these two criteria, each participant was assigned with a number by an experimenter who did not take part in the experiment. Odd numbers received the caffeinated energy drink and placebo beverage order while even numbers received the placebo beverage and caffeinated energy drink order. The experimental trials were separated by 1 week to allow complete caffeine washout. On one occasion, participants ingested 3mg caffeine/kg body mass (3mg/kg) by means of a powdered caffeine-containing energy drink (Furew; Pro-Energetics) dissolved in 250ml of tapwater.Onanother occasion, participants ingested the same amount of energy drink but with no caffeine content (placebo; 0mg/kg). The two experimental drinks had a similar taste and appearance and they only differed in the amount of caffeine they contained. The energy drinks also contained taurine (18·7mg/kg), sodium bicarbonate (4·7 mg/kg), L-carnitine (1·9 mg/kg) and maltodextrin (6·6mg/kg); however, these substances were ingested in identical proportions in the two experimental trials. Both experimental trials were performed at the same time of the day to avoid the effects of circadian rhythms in the studied variables(31). The experimental beverages were ingested 60 min before the onset of the experimental trials to allow for complete caffeine absorption(32), and they were provided in opaque plastic bottles to avoid identification. An alphanumeric code was assigned to each trial to blind participants and investigators to the beverage tested. Standardisation The day before each experimental trial, participants were nude weighed (+/-50 g; Radwag) to calculate the amount of caffeine required for each individual caffeinated energy drink. The amount of the energy drinks was individually calculated to avoid the effects of body mass on the variables under investigation. On that day, participants refrained from strenuous exercise and adopted a similar diet and fluid intake regimen. Participants were encouraged to withdraw from all dietary sources of caffeine (coffee, cola drinks, chocolate, etc.) and alcohol 48 h before testing. In addition, participants were instructed to have a light meal at least 2 h before the onset of the experimental trials. These standardisations were reported to the technical staff of the teams and food and fluid diaries were obtained to ensure compliance. Experimental protocol On the day of testing, participants ingested the corresponding beverage (caffeine-containing energy drink or placebo energy drink) and completed a specific sport session, including a standardised warm-up and a simulated competition. Thereafter, participants were required to fill out a questionnaire about their sensations of muscle power, endurance and perceived exertion (RPE) during the test. This questionnaire included a 1- to 10- point scale to assess each item, and participants were previously informed that 1 point meant minimal amount of that item and 10 points meant maximal amount of the item. Moreover, participants were asked to indicate on a yes/no scale whether they had had any perceptible effect. In addition, participants were provided with a survey to be filled out before going to sleep about nervousness, gastrointestinal problems, muscular pain, headache and activeness they had perceived in the hours after the drink ingestion. In the following morning after the ingestion of the energy drinks, participants were asked about sleep quality (e.g. insomnia) on a yes/no scale and about perceived fatigue on a 1- to 10-point scale. This survey has been previously used to assess side effects resulting from energy drink ingestion(20). Participants who did not complete these questionnaires on time were eliminated from the analysis. Thus, eight participants were excluded from the statistical analysis based on this criterion, as indicated in the ‘Participants’ section. Statistical analysis Results of quantitative data are presented as means and standard deviations. Differences in the 1- to 10-point scale were analysed using the Wilcoxon signed-rank test. Effect size was calculated (Cohen’s d) for each item. Results of qualitative data (e.g. side effects) are presented as percentages. Differences in side effects after beverage intake were analysed using the McNemar test. Sex influences on the tested variables were verified by using a general linear model and a two-way repeated-measures ANOVA (beverage £ sex). The criterion for statistical significance in all these tests was set at P,0·05. The SPSS for Windows 19.0 statistical package (SPSS, Inc.) was used to analyse the data.|
|How many outcome-specific endpoints are evaluated?||5|
|What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately)||sleep|
|List additional health endpoints (separately).||fatigue|
|List additional health endpoints (separately)|
|Notes||sleep was measured as insomnia|
|What is the study design?||Controlled Trial|
|Randomized or Non-Randomized?||RCT|
|What were the diagnostics or methods used to measure the outcome?||Subjective|
|Optional: Name of Method or short description||questionnaire|
|Energy drinks||Energy drinks|
|What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.)||placebo (0 mg caffeine in energy drink mixture) or 3 mg/kg caffeine in energy drink mixture|
|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|
|Provide a general description of results (as reported by the authors).||In the morning after the intake of the experimental beverage, females showed higher perceived fatigue after the intake of the placebo beverage (d = 0·17; P=0·035), while males showed no effect (d = 0·08; P=0·109; Table 3) . There was a statistically significant effect observed for sex interaction (P=0·008). The ingestion of the caffeinated energy drink produced a higher prevalence of side effects such as insomnia (31·2% caffeine v. 10·4% placebo; P,0·001), nervousness (13·2% caffeine v. 0% placebo; P=0·002) and activeness (16·9% caffeine v. 3·9% placebo; P=0·007) than the ingestion of the placebo energy drink (Table 4). In these three variables, there were significant differences in the female subpopulation, while in the male subpopulation there were only significant differences between caffeine and placebo in the prevalence of insomnia. There were no sex differences in the incidence of side effects (sex x beverage interaction; P.0·05).|
|Did the authors perform a dose-response analysis (or trend/related analysis)?||No|
|What were the authors's observations re: trend analysis?|
|What were the author's conclusions?||In comparison to the placebo beverage, ingestion of the caffeinated energy drink enhanced the subjective perception of muscle power during exercise and reduced overall fatigue the following morning after the intake of the beverage. Moreover, the caffeinated energy drink increased the prevalence of side effects such as insomnia, activeness and nervousness. Interestingly, the caffeinated energy drink affected both male and female participants in a similar manner. In conclusion, the ingestion of a caffeinated energy drink (3mg caffeine/kg body mass) improved perceived muscle power during intense exercise, although it did not affect subjective feelings of endurance or exhaustion. Following the exercise bout, the ingestion of the caffeine-containing energy drink significantly increased the prevalence of side effects, such as insomnia, activeness and nervousness. The presence of these side effects was similar between male and female participants. These data indicate that energy drinks produce minor side effects, and special attention should be paid to these beverages when they are ingested in the afternoon.|
|What were the sources of funding?||The present study received no specific grant from any funding agency, commercial or not-for-profit sectors.|
|What conflicts of interest were reported?||None of the authors has any conflicts of interest to declare.|
|Does the exposure (dose) need to be standardized to the SR?||Yes|
|Provide calculations/conversions for the exposure based on the decision tree in the guide (for all endpoints/exposure levels of interest).||3 mg/kg dose x 70.4 kg (mean body weight, from study) = 211 mg/day caffeine|
|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.||sleep - LOAEL = 211 mg/day caffeine (sleep disturbances) nervousness - LOAEL = 211 mg/day caffeine headache - NOAEL = 211 mg/day caffeine irritable - NOAEL = 211 mg/day caffeine fatigue - NOAEL = 211 mg/day caffeine|
|Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot.||single dose effects seen at levels less than Nawrot. caffeine improved ratings of fatigue relative to placebo, in women.|
|What is the importance of the study with respect to the adverseness of the outcome?||Important|
No baseline characteristics have been defined for this extraction form.
Results & Comparisons
No Results found.
|Arm or Total||Title||Description||Comments|
No quality dimensions were specified.
No quality rating data was found.