In a recent study published in Nutrients, researchers analyzed the placebo effect of caffeine ingestion on running performance.
Study: Belief That Caffeine Ingestion Improves Performance in a 6-Minute Time Trial Test without Affecting Pacing Strategy. Image Credit: lymenko Mariia/Shutterstock.com
Background
The placebo effect has been studied in psychology and medicine in different clinical conditions. In recent years, interest in sports research has increased, with reports suggesting small to moderate performance improvements.
The placebo effect in sports is mainly studied from the perspective of ergogenic aids, such as bicarbonate, amino acids, or carbohydrates. However, placebo research in sports performance is linked to caffeine.
Since the pharmacological and expectancy effects of the ergogenic aid influence performance, caffeine is an ideal candidate to influence an athlete’s expectancies.
Data suggest that caffeine has increased in sports, with three-fourths of elite athletes taking caffeine during competitions.
The ergogenic effects of caffeine on endurance have been characterized, and athletes are more likely to have (positive) expectancies. Nevertheless, studies investigating placebos for improved performance are limited.
About the study
In the present study, researchers examined the placebo effect of caffeine ingestion on performance during a six-minute time-trial (TT) test. Individuals with regular running training (≥ 3 days/week) the past year were recruited.
The team implemented a randomized, counterbalanced, and repeated experimental design to compare the effects of caffeine ingestion (placebo) and control (no ingestion).
Each participant performed two TT tests seven days apart. Six participants started with the placebo condition, and seven started with the control condition. Subjects were instructed to avoid heavy exercise and caffeine intake 48 hours before the test.
They adopted a similar diet, fluid regimen, and sleep pattern 24 hours before each test. Both tests were conducted at the same time of the day to preclude the effects of circadian rhythm.
Participants were informed of caffeine’s ergogenic properties and associated performance improvements. Before the test, participants took a warm-up session involving 15 minutes of continuous running, running drills, mobility exercises, and 150m progressive runs.
Participants rested after warming up and were asked to cover the maximum possible distance at constant speed. The distance covered in six minutes was determined.
The pacing strategy was analyzed using partial times for each 400m. A power meter device was used to measure the kinematic variables of the gait cycle (contact time, step frequency, and vertical oscillation).
Participants received chewing gum while warming up and were informed it would allow optimal dose absorption to enhance performance. However, the gums did not contain caffeine or other psychoactive substances.
A day after the test, a questionnaire was administered to capture information on side effects. The Shapiro-Wild test assessed the normality of variables.
Differences between conditions were examined using t-tests for paired samples; the Wilcoxon test was used for variables without normal distribution, and the student’s t-test was used for normally distributed variables. Analysis of variance was performed for variables measured during the 400 m splits.
Findings
Belief in caffeine ingestion resulted in improved test performance. Eight individuals improved performance in the placebo condition, but five subjects did not.
There were no interactions between the pacing strategy and condition. However, a significant main effect was observed for the split. Pacing was U-shaped in both conditions, with faster starts and finishes.
Pairwise comparisons revealed greater speed during the second and third splits in the placebo condition.
Heart rate remained consistent between conditions, without significant interactions between split and condition, and progressively increased in each split. The rate of perceived exertion was also comparable between conditions.
Furthermore, no significant interactions were noted between split and condition in any kinematic variable. Side effects reported by participants were similar between conditions.
Three participants reported heightened activeness following placebo ingestion. No participant experienced sleeping problems.
Conclusions
The study examined the placebo effect of caffeine ingestion on running performance and pacing strategy during a six-minute TT test.
The team observed that belief in caffeine ingestion increased the distance covered in the placebo condition. There was no effect on heart rate, pacing strategy, kinematic variables, and rate of perceived exertion.
Overall, belief in caffeine increased distance by 1.6% or 46 m during the test without impacting the pacing strategy.
Thus, recreationally trained individuals could improve by approximately five seconds in 1,500 m competitions. Placebo use could be a wise strategy to enhance performance without the need for psychoactive substances.
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