Placebo Effect in Field-Based Physical Performance

Psychophysiological Mechanisms of the Placebo Effect on Physical Performance in Field Settings

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.

Study Overview

• Status: Not yet recruiting
• Conditions: Cognitive Performance; Placebo Effect; Physical Performance
• Intervention / Treatment: Drug: Caffeine (6mg/kg); Other: Placebo (Starch capsule); Other: Sham (No Treatment)

Detailed Description

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
• Enrollment (Estimated): 120
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Jakub Malik, PhD; Phone Number: +48739975701; Email: malik@awf.poznan.pl

Study Locations

• Poland
  • Greater Poland Voivodeship
    • Poznan, Greater Poland Voivodeship, Poland
      • Poznań University of Physical Education
      • Contact: Jakub Malik, PhD; Phone Number: +48739975701; Email: malik@awf.poznan.pl

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Age between 20 and 35 years,
• Healthy adults,
• Regular physical activity,
• 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.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Caffeine Group; Participants ingest a single dose of caffeine (6mg/kg body mass) prior to a field-based exercise protocol (e.g., Cooper test or Repeated Sprint Ability).	Drug: Caffeine (6mg/kg); Anhydrous caffeine administered in an encapsulated form at a dosage of 6mg per kilogram of body mass, 30-60 minutes before the exercise protocol.
Active Comparator: Placebo Group; Participants ingest a single dose of placebo (corn starch) in an identical capsule prior to a field-based exercise protocol.	Other: Placebo (Starch capsule); Corn starch administered in an identical encapsulated form as the active caffeine, 30-60 minutes before the exercise protocol.
Sham Comparator: Control Group; Participants perform the same field-based exercise protocol without ingesting any capsule or active substance.	Other: Sham (No Treatment); Participants perform the same exercise protocols without any capsule or substance administration.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
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.	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.	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.	Measured during the exercise protocol immediately following administration of the study intervention.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Exercise Heart Rate (bpm)	Heart rate (beats per minute) recorded continuously throughout the standardized exercise protocol.	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.	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.	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).	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).	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.	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.	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.	Continuously monitored during the exercise protocol immediately following administration of the study intervention.
Anthropometric Indices (kg)	Body mass expressed in kilograms.	Measured at the start of the protocol.
Anthropometric Indices (m)	Height expressed in metres.	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.	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.	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.	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.	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.	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.	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.	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).	Measured immediately before and immediately after the exercise protocol.
Performance Expectancy (points)	Measured immediately before the exercise protocol following administration of the study intervention.	Measured immediately after completion of the exercise protocol.

Collaborators and Investigators

• Sponsor: Poznan University of Physical Education
• Investigators: Principal Investigator: Jakub Malik, PhD, Poznan University of Physical Education, Department of Sports Psychology

Study record dates

Study Major Dates

• Study Start (Estimated): September 1, 2026
• Primary Completion (Estimated): March 31, 2028
• Study Completion (Estimated): March 31, 2029

Study Registration Dates

• First Submitted: July 21, 2026
• First Submitted That Met QC Criteria: July 31, 2026
• First Posted (Actual): August 3, 2026

Study Record Updates

• Last Update Posted (Actual): August 3, 2026
• Last Update Submitted That Met QC Criteria: July 31, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Caffeine; Psychophysiology; Expectancy; Postural Control; Exercise Physiology; Human Performance
• Additional Relevant MeSH Terms: Heterocyclic Compounds; Heterocyclic Compounds, 2-Ring; Heterocyclic Compounds, Fused-Ring; Dietary Carbohydrates; Carbohydrates; Alkaloids; Purinones; Purines; Polymers; Macromolecular Substances; Polysaccharides; Glucans; Biopolymers; Xanthines; Caffeine; salicylhydroxamic acid; Starch
• Other Study ID Numbers: 152-1-26; 2025/57/N/NZ4/04470 (Other Grant/Funding Number: National Science Centre)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED
• IPD Plan Description: The decision regarding the sharing of individual participant data has not yet been finalized. We are currently evaluating the feasibility, ethical considerations, and data privacy requirements for potential data sharing. A formal plan will be developed and implemented in accordance with institutional policies and regulatory standards upon the completion of the study.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No