This study aims to investigate the placebo (PLA) effect on physical performance across different sports disciplines in real-world, field-based settings. The study investigates how participant expectations and beliefs regarding caffeine (CAF) intake influence physical performance and psychomotor function outside the controlled laboratory environment. Healthy, physically active adults (n = 120) from diverse sports backgrounds will be randomly assigned to receive caffeine, placebo, or no intervention. Participants will perform discipline-specific field exercise tests (e.g., running-based protocols or repeated sprint protocols) while physiological responses are monitored using wearable technology. Physical performance outcomes and psychomotor responses will be analyzed to evaluate the real-world impact of the placebo effect and to distinguish the pharmacological effects of caffeine from those driven by psychological expectations across different athletic settings.
This study employs a cross-sectional design conducted in diverse field settings to investigate the placebo (PLA) effect across different sports disciplines. Participants (n = 120, aged 20-35 years) representing different training profiles (endurance and mixed) will be randomly assigned to one of three parallel groups: Caffeine, Placebo, or Control. Each participant will complete a single experimental session lasting approximately 35 minutes, consisting of: (1) baseline psychomotor assessment using the Simple Reaction Time test, (2) a discipline-specific exercise protocol (e.g., the Cooper test performed on an athletics track or a Repeated Sprint Ability protocol), and (3) post-exercise recovery monitoring. Physiological parameters, including heart rate (HR), heart rate variability (HRV), and respiratory rate (RR), together with postural stability, will be continuously monitored using wearable technology. The study will evaluate how psychological expectations influence physical performance, psychomotor function, and physiological responses during sport-specific exercise, providing evidence for the role of the placebo effect under real-world athletic conditions.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
QUADRUPLE
Enrollment
120
Anhydrous caffeine administered in an encapsulated form at a dosage of 6mg per kilogram of body mass, 30-60 minutes before the exercise protocol.
Corn starch administered in an identical encapsulated form as the active caffeine, 30-60 minutes before the exercise protocol.
Participants perform the same exercise protocols without any capsule or substance administration.
Poznan University of Physical Education
Poznan, Greater Poland Voivodeship, Poland
Physical Performance Capacity (total distance in running, metres)
Total physical work capacity measured as the total running distance (metres) completed during the standardized exercise protocol.
Time frame: Measured during the exercise protocol immediately following administration of the study intervention.
Physical Performance Capacity (total work in Joules for cycling)
Total physical work capacity measured as the total mechanical work (Joules) completed during the standardized cycling exercise protocol.
Time frame: Measured during the exercise protocol immediately following administration of the study intervention.
Physical Performance Capacity (exercise duration until exhaustion, minutes)
Total physical work capacity measured as exercise duration until volitional exhaustion during the standardized exercise protocol.
Time frame: Measured during the exercise protocol immediately following administration of the study intervention.
Exercise Heart Rate (bpm)
Heart rate (beats per minute) recorded continuously throughout the standardized exercise protocol.
Time frame: Continuously monitored during the exercise protocol immediately following administration of the study intervention.
Cognitive Heart Rate (bpm)
Heart rate recorded during standardized cognitive performance tasks.
Time frame: Measured during cognitive testing immediately before and immediately after the exercise protocol.
Post-Exercise Heart Rate Recovery (bpm)
Heart rate recorded during the post-exercise recovery period.
Time frame: Continuously monitored during the first 5 minutes immediately following completion of the exercise protocol.
Cognitive Reaction Time (ms)
Reaction time measured during standardized cognitive tasks (e.g., Psychomotor Vigilance Test, Stroop Test, Flanker Test).
Time frame: Measured immediately before and immediately after the exercise protocol.
Rating of Perceived Exertion (Borg Scale, points)
Perceived exertion assessed using the Borg Rating of Perceived Exertion Scale (6-20).
Time frame: Measured immediately after completion of the exercise protocol.
Biomechanical Kinematic Profile (cm)
Continuous recording of kinematic parameters derived from wearable sensors, including step length and vertical oscillation.
Time frame: Continuously monitored during the exercise protocol immediately following administration of the study intervention.
Biomechanical Kinematic Profile (ms)
Continuous recording of stance time derived from wearable sensor data.
Time frame: Continuously monitored during the exercise protocol immediately following administration of the study intervention.
Biomechanical Kinematic Profile (steps/min)
Continuous recording of cadence derived from wearable sensor data.
Time frame: Continuously monitored during the exercise protocol immediately following administration of the study intervention.
Anthropometric Indices (kg)
Body mass expressed in kilograms.
Time frame: Measured at the start of the protocol.
Anthropometric Indices (m)
Height expressed in metres.
Time frame: Measured at the start of the protocol.
Body composition (fat-free mass, fat mass) (kg)
Assessment of body composition (fat-free mass, fat mass) (kg) will be performed at the start of the protocol.
Time frame: Measured at the start of the protocol.
Body composition (fat-free mass, fat mass) (%)
Assessment of body composition (fat-free mass, fat mass) (%) will be performed at the start of the protocol.
Time frame: Measured at the start of the protocol.
Body composition (total body water) (L)
Assessment of body composition (total body water) (L) will be performed at baseline at the start of the protocol.
Time frame: Measured at the start of the protocol.
Body composition (total body water) (%)
Assessment of body composition (total body water) (%) will be performed at baseline at the start of the protocol.
Time frame: Measured at the start of the protocol.
Exercise Heart Rate Variability (ms)
Heart rate variability recorded continuously throughout the standardized exercise protocol to assess autonomic regulation.
Time frame: Continuously monitored during the exercise protocol immediately following administration of the study intervention.
Cognitive Heart Rate Variability (ms)
Heart rate variability recorded during standardized cognitive performance tasks.
Time frame: Measured during cognitive testing immediately before and immediately after the exercise protocol.
Post-Exercise Heart Rate Variability Recovery (ms)
Heart rate variability recorded during the post-exercise recovery period.
Time frame: Continuously monitored during the first 5 minutes immediately following completion of the exercise protocol.
Cognitive Accuracy (%)
Accuracy measured during standardized cognitive tasks (e.g., Psychomotor Vigilance Test, Stroop Test, Flanker Test).
Time frame: Measured immediately before and immediately after the exercise protocol.
Performance Expectancy (points)
Measured immediately before the exercise protocol following administration of the study intervention.
Time frame: Measured immediately after completion of the exercise protocol.
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