Effect of caffeine ingestion on high-intensity intermittent exercise performance in athletes
Whelan, Heather Kim
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To determine whether acute caffeine ingestion improves high-intensity intermittent exercise performance, 17 college-level, competitive athletes (9 males, 8 females, mean age 22 years) performed caffeine and placebo trials in a double-blind randomized study. Caffeine and placebo (lactose) doses of 6 mg/kg body weight (rounded to nearest 100 mg) were given in 100 mg capsules; a dose consistently shown to produce urine caffeine levels below the maximum permitted by the International Olympic Committee. Habitual caffeine consumption, usual physical activity level, and food intake for 3 days prior to each trial were determined by questionnaire. At each trial, one week apart, subjects performed three 30 second sprints on a treadmill (7.5 mph, 20% incline) separated by 2 minutes of walking, followed by a final sprint to exhaustion. Time to exhaustion (TM-EXH) was recorded and ranged from 20-90 seconds. Subjects reported a rating of perceived exertion (RPE) at the end of each sprint. Fingertip blood lactate (LACT) was measured following the third 30 second sprint, final sprint, and after 5 minutes of recovery. Respiratory variables were measured throughout the trial and the respiratory exchange ratio (RER) was determined for each sprint and recovery period within each trial. Repeated measures ANOVA showed no significant differences between the caffeine and placebo trials for TM-EXH, RPE, LACT, or RER. However, although not significant, there was an average increase in TM-EXH during the caffeine trial by 2 seconds (4%); with 6 of 9 males and 5 of 8 females running longer during the caffeine trial. Habitual caffeine consumption did not appear to influence the results. In conclusion, the ingestion of caffeine prior to high intensity intermittent exercise seems to improve performance by a narrow and statistically non-significant margin. Note:Page 99 has been removed due to copyright reasons.