Study Title and Description
Caffeinated chewing gum increases repeated sprint performance and augments increases in testosterone in competitive cyclists.
Key Questions Addressed
|1||For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on reproductive and developmental outcomes?|
Primary Publication Information
|Title||Caffeinated chewing gum increases repeated sprint performance and augments increases in testosterone in competitive cyclists.|
|Author||CD Paton,T Lowe,A Irvine,|
Secondary Publication Information
There are currently no secondary publications defined for this study.
Extraction Form: Reproductive Toxicity - Design Details
No arms have been defined in this extraction form.
|Question... Follow Up||Answer||Follow-up Answer|
|What outcome is being evaluated in this paper?||Reproductive and Development|
|What is the objective of the study (as reported by the authors)?||Given the limited and inconsistent findings in the literature regarding the effects of caffeine on repeated high intensity, intermittent exercise, the purpose of this study was to investigate the effects of caffeine, delivered via a novel method (chewing gum), on fatigue during repeated high-intensity sprints in well-trained cyclists. Furthermore, in an attempt to gain an understanding of the effects of caffeine on hormonal activity during intense exercise the acute salivary cortisol and testosterone responses were also investigated.|
|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)||The study was a balanced, placebo controlled, double blind, cross-over trial. Nine well-trained male cyclists completed this study. Dietary control: Prior to commencing the study subjects were provided with a comprehensive list of common dietary caffeine sources including food, beverages, medicines and supplements; subjects were asked to identify any caffeinated products that they regularly consumed as part of their diet. Cyclists were also required to complete a 3-day food diary in order to confirm that they were habitually low to moderate (<300 mg per day) caffeine users; regular high dose (>500 mg per day) caffeine users were excluded from the study. During the 24 h prior to the experimental trials, cyclists were instructed to prepare for the session as though it were a competition, and to abstain from caffeine consumption. Caffeine administration: Immediately following the second exercise set, after the collection of a second saliva sample, cyclists received either the placebo or caffeine treatment. Caffeine was administered as an absolute dose (240 mg), as six pieces of commercially available (spearmint flavoured) caffeinated chewing-gum (Jolt caffeine-energy gum, Gum Runners, Hackensack, NJ, USA). Cyclists chewed the gum for 5 min and were then required to expectorate the chewed gum into a container. Saliva collection and analysis: Saliva samples were collected upon arrival to the laboratory (baseline), and immediately following each set of five sprints. A further four samples were collected immediately following sets one to four. Saliva samples were immediately frozen at- 20 C until radioimmunoassay (RIA). Saliva samples were analysed in triplicate for testosterone and cortisol using radioimmunoassay. Statistical analyses: Effects of caffeine on performance and salivary hormone concentrations were expressed in raw units, as percentage changes, and as standardised effects. Magnitudes of the standardised effects were interpreted and reported using the modified Cohen effect thresholds of: 0.2, 0.5, and 0.8 for small, moderate, and large, respectively, in accordance with the recommendations and guidelines of Hopkins (2002 ).|
|How many outcome-specific endpoints are evaluated?||1|
|What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately)||salivary testosterone|
|List additional health endpoints (separately).|
|List additional health endpoints (separately)|
|Notes||Cortisol also evaluated but was not included for purposes of SR|
|What is the study design?||Controlled Trial|
|Randomized or Non-Randomized?||RCT|
|What were the diagnostics or methods used to measure the outcome?||Objective|
|Optional: Name of Method or short description||RIA|
|Caffeine (general)||Caffeine (general)|
|What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.)||Placebo vs exposed|
|What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models. Copy from methods)||NA|
|Provide a general description of results (as reported by the authors).||The main finding for testosterone was that following the chewing of caffeinated gum, subjects experienced a mean increase of 12%; ± 14% (90% CL) relative to the placebo condition with a moderate effect size of 0.50; ± 0.56 (90% CL). The main finding for cortisol was that following the chewing of caffeinated gum, subjects showed a relative decrease of 21%; ± 31% compared to placebo, equivalent to a moderate effect size of - 0.30; ± 0.34.|
|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 conclusion, results of the study show that a moderate dose (~3 mg kg-1) of caffeine delivered by chewing gum is ergogenic and can delay fatigue during repeated high intensity, intermittent sprint exercise. The key findings in this study were that caffeine, administered via a novel method, led to substantial improvements in performance during repeated sprint cycling by reducing the rate of accumulated fatigue over four exercise sets. The decrease in fatigue following caffeine ingestion was associated with moderate increases in testosterone of ~12% whereas cortisol showed a moderate decrease of ~21% relative to the placebo condition.|
|What were the sources of funding?||The authors gratefully acknowledge the funding provided by the Waikato Institute of Technology to enable this study, and the assistance of Dr. David Rowlands on manuscript preparation.|
|What conflicts of interest were reported?||The authors received no assistance from any commercial company whose products were used in the study, and report no conflict of interest with this study and its results.|
|Does the exposure (dose) need to be standardized to the SR?||No|
|Provide calculations/conversions for the exposure based on the decision tree in the guide (for all endpoints/exposure levels of interest).|
|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.||NOEL = 240 mg for acute increase in salivary testosterone|
|Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot.||90%CL was not stat sig, thus was regarded as a NOEL authors evaluated cortisol as well; did not include in comparisons|
|What is the importance of the study with respect to the adverseness of the outcome?||Low|
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.