Caffeine (6mg/kg): Anhydrous caffeine administered in an encapsulated form at a dosage of 6 mg per kilogram of body mass, 60 minutes before the exercise protocol.
Placebo (Starch capsule): Corn starch administered in an identical encapsulated form as the active caffeine, 60 minutes prior to the laboratory exercise protocol.
Study summary
This study aims to determine the impact of the placebo (PLA) effect on physical and cognitive performance in a controlled laboratory setting. The study investigates how expectations and beliefs about substance intake (caffeine vs. placebo) interact with actual consumption to influence performance and physiological stress markers. Healthy adults (n = 80) will participate in four testing sessions using a randomized, double-blind, placebo-controlled crossover design. Physiological stress markers (cortisol and alpha-amylase), heart rate, and performance metrics will be monitored during a standardized cycling exercise protocol. This phase provides the dense mechanistic data required to refine a mathematical model of the placebo effect, offering insights into how individual personality traits and cognitive anchoring influence psychophysiological potential.
Eligibility
Sex
ALL
Min age
20 Years
Max age
35 Years
Healthy volunteers
Accepted
Inclusion Criteria:
* Age between 20 and 35 years,
* Healthy adults,
* Regular physical activity, but not professional athletes,
* Normal or corrected-to-normal vision,
* Habitual caffeine consumption.
Exclusion Criteria:
* History of neurological, psychiatric, cardiovascular, or metabolic disorders,
* Current use of medication or supplements affecting the central nervous system,
* Musculoskeletal injuries that would impair physical performance,
* No habitual caffeine consumption or severe negative side effects of caffeine,
* Diagnosed sleep disorders or chronic fatigue,
* Diagnosed major depressive disorder or other severe psychiatric conditions,
* Presence of any menstrual disorders,
* Inability to attend all experimental study visits.
Primary outcome measure(s)
Physical Work Capacity (total work in J) — Measured during each laboratory exercise protocol (approximately 85-120 minutes). Total physical work performed, expressed in Joules (J), during the standardized laboratory exercise protocol, including both the Anaerobic Threshold phase and the Self-paced Maximal Time-trial.
Psychomotor Vigilance Test Reaction Time (ms) — Measured at T1 (pre-ingestion, minute 2 of the protocol), T2 (post-ingestion/pre-exercise, minute 55 of the protocol), and T3 (post-exercise, minute 125 of the protocol). Reaction time during the Psychomotor Vigilance Test expressed in milliseconds (ms).
Flanker Test Reaction Time (ms) — Measured at T1 (pre-ingestion, minute 2 of the protocol), T2 (post-ingestion/pre-exercise, minute 55 of the protocol), and T3 (post-exercise, minute 125 of the protocol). Reaction time during the Flanker Test expressed in milliseconds (ms).
Postural Control (mm) — Measured continuously during the exercise protocol and at T1 (minute 2), T2 (minute 55), and T3 (minute 125). Center of Pressure excursions measured using the BTrackS Balance Plate and expressed in millimeters (mm).
Explosive power variables (mm) — Continuous recording throughout the exercise protocol and discrete assessments at T1 (2 minute of protocol), T2 (55 minute of protocol), and T3 (125 minute of protocol). Explosive lower-limb power expressed in millimeters (mm) - Countermovement Jump - height.
Trial sites (1)
Facility
City
Region
Status
Poznan University of Physical Education
Poznan
Wielkopolska
More Poznan University of Physical Education trials in Poland
This page summarises publicly available registry data for informational purposes — not medical advice. Eligibility is determined by each study team; patients should discuss participation with their clinician.
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