Study Preview
Study Title and Description
The effect of caffeine on performance in collegiate tennis players
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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| Title | The effect of caffeine on performance in collegiate tennis players |
| Author | C. S. Klein, A. Clawson, M. Martin, M. J. Saunders, J. A. Flohr, M. K. Bechtel, W. Dunham, M. Hancock and C. J. Womack |
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| Year | 2012 |
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Secondary Publication Information
There are currently no secondary publications defined for this study.
Extraction Form: Cardiovascular Design
| Question... Follow Up | Answer | Follow-up Answer | |
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| 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)? | The purpose of this study was to determine the effect of caffeine supplementation on simulated match performance in collegiate tennis players, and to ascertain whether this polymorphism influences the magnitude of the putative ergogenic effects of caffeine supplementation. |
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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 Twenty NCAA Division I tennis players (10 men; 10 women) (18–24 years), participating on the same collegiate tennis team, volunteered for this study. Two participants did not maintain consistent training throughout the study period (due to injuries unrelated to the study), and thus were dropped from the data analysis. Two other subjects were excluded after they were unable to provide sufficient samples for genotyping; therefore, 8 men and 8 women participated in the study. Participants self-reported average weekly intake of coffee, tea, soda, chocolate, and other caffeinated beverages. Approximate milligram doses were assigned, and an approximate daily intake was obtained. Based on previous criteria, participants were characterized as having low (0–150 mg/day), moderate (151–300 mg/day), and high ( > 300 mg/day) caffeine intake. Testing Procedures Subjects performed a total of four exercise trials in the study: a maximal exercise test, familiarization trial, and two experimental trials (described below). A minimum of 2-day recovery was provided between the experimental trials. Maximal exercise test. The test began with subjects running at a self-selected pace between 6.0 and 7.0mph on Stairmaster Club track treadmill (Kirkland, WA) at 0% grade for 1 minute. Every subsequent minute, the treadmill (TM) grade was increased by 2% until volitional fatigue. Familiarization trial. Subjects completed a familiarization trial for the experimental trials described below. All protocols and procedures mimicked those used in the experimental trials. However, subjects received no supplementation before the familiarization trial. Tennis test. Subjects completed two separate exercise sessions with each session consisting of a treadmill (TM) test followed by a tennis skills test (TST). The tests were performed in the morning following a 12-hour fast. The participants were instructed to avoid consumption of food and beverages containing caffeine for 24 hours before the tests. One hour before testing, subjects ingested a capsule containing either 6mg of anhydrous caffeine per kilogram of body weight (Terra Vita; Brampton, Canada) or placebo (white flour), administered in a doubleblind fashion. The TM test began with a 15-minute warm-up at a speed corresponding to 50% VO2max followed by 30 minutes of TM work (which consisted of a total of 54 high-intensity repetitions [18, 12, 12, and 12, separated by 90 seconds rest]). Two minutes following the TM test, the TST was administered, which consisted of 9 intervals separated by 20 or 90 seconds of rest. Each interval included six sets of six different shots (four ground strokes, one approach shot, and one volley) to emulate a single game within a set of tennis. Subjects were tested indoors, and ball feeding was conducted by the same highly skilled tennis coach throughout all trials. A small (n = 6) cohort of tennis players performed repeated tests of the TST to establish the reliability of this skill test. Coefficient of variation from this sample was 0.7%. HR was obtained using a Polar heart rate monitor. During the TM test, HR was were recorded upon completion of the interval immediately preceding the 90-second rest period for a total of five measurements, which were then averaged. HR was recorded after a 12-interval block throughout the TST, with a final reading at the end of the last interval. These five readings were used to determine average scores. Genotyping DNA was obtained from whole-blood samples via a QiaAmp mini-blood kit (Qiagen, Inc., Valencia, CA). Restriction fragment length polymorphism–polymerase chain reaction (RFLP-PCR) was used for genotyping. participants were grouped as AA homozygotes and C allele carriers. Investigators were blinded to the genotype until all subjects completed the study. Furthermore, all genotyping was performed by an investigator not involved with the performance testing. Statistical Analysis SPSS 16.0 (Thomson Learning, Pacific Grove, CA) was used for statistical analyses. Potential differences in average HR during the TM test and average HR during the TST were assessed using repeated measures analysis of variance (RMANOVA) with treatment (caffeine; placebo) as the within-subjects factor and the genotype (AA homozygotes; C allele carriers) as the between-subjects factor. An a priori RMANOVA was performed for successful shots in the TST, and no significant (p > 0.05) gender or gender x treatment interaction was observed. Thus, the results for male and female participants were pooled for subsequent analysis. For all RMANOVA procedures, post hoc tests were performed using independent and dependent t-tests with a Bonferroni correction. Significance was determined at an alpha level of p < 0.05. |
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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? | 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 | Polar heart rate monitor |
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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.) | Treatment (caffeine; placebo) was the within-subjects factor and the genotype (AA homozygotes; C allele carriers) was the between-subjects factor in a RMANOVA. |
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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 competing financial interests exist. |
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| Refid | 10258 |
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| What were the sources of funding? | None reported |
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Results & Comparisons
No Results found.
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