Physical PerformanceNCT07748429
Placebo Effect on Cycling Performance: Laboratory Crossover Study
A study testing Caffeine (6mg/kg) in people with Physical Performance and Placebo Effect, run by Poznan University of Physical Education at 1 site in Poland.
Trial 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. Read more about this study
- Who is it for?
- Ages 20 to 35 yearsHealthy volunteers can take part
- Conditions the study is for
- Physical Performance, Placebo Effect, Cognitive Performance
- What is being tested?
- Caffeine (6mg/kg)
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 80 participants
- Where
- 1 sitePoland
- Study dates
- 1 Jan 2027to 31 Mar 2029
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 20 to 35 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Age between 20 and 35 years,
- Healthy adults,
- Regular physical activity, but not professional athletes,
- Normal or corrected-to-normal vision,
- Habitual caffeine consumption.
Who cannot join
- 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.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Poland1 site
Poznan University of Physical Education
Poznan, Wielkopolska
Jakub Malik, PhD, +48739975701, malik@awf.poznan.pl
About this study
Official title: The Impact of Expectations on Physical Performance and Psychophysiological Potential: a Randomized, Double-blind, Placebo-controlled Crossover Study on the Placebo Effect in the Context of Caffeine Supplementation
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.
Read the detailed description
This study employs a randomized, double-blind, placebo-controlled crossover design to conduct a multifactorial analysis of psychophysiological and biomechanical dynamics. Participants (n = 80, aged 20-35 years) will complete four experimental sessions separated by 7-day washout periods, involving caffeine (6 mg/kg) or placebo administration. The laboratory protocol (160 minutes) integrates multiple modalities: (1) cognitive testing (Reaction Time Test and Flanker Test), (2) postural control assessment using the BTrackS Balance Plate, and (3) a standardized cycle ergometer exercise protocol consisting of 15 minutes at the anaerobic threshold followed by a 5-minute self-paced maximal effort trial. Belief manipulation (immediate vs. retrospective reporting) and cognitive anchoring (feedback conditions) are implemented to isolate expectancy-driven effects. Continuous metabolic and cardiorespiratory data collected using the Cosmed K5 system will be synchronized with blood biomarkers (lactate, glucose, caffeine, and paraxanthine) and salivary biomarkers (cortisol, testosterone, and alpha-amylase). Advanced statistical methods, including Functional Data Analysis (FDA) and machine learning, will be used to integrate physiological trajectories with behavioral predictors.
- Conditions
- Physical Performance, Placebo Effect, Cognitive Performance
- Being tested
- Caffeine (6mg/kg), Placebo (Starch capsule)
- Keywords
- Caffeine, Expectancy, Psychophysiology, Exercise PHysiology, Postural Control, Human Performance
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Caffeine (6mg/kg)Drug
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)Other
Corn starch administered in an identical encapsulated form as the active caffeine, 60 minutes prior to the laboratory exercise protocol.
| Study group | Role | What they receive |
|---|---|---|
| Sequence AABB | Experimental | Participants follow the sequence: Caffeine, Caffeine, Placebo, Placebo, with a 7-day washout period between sessions. Receives: Drug: Caffeine (6mg/kg); Other: Placebo (Starch capsule) |
| Sequence BBAA | Experimental | Participants follow the sequence: Placebo, Placebo, Caffeine, Caffeine, with a 7-day washout period between sessions. Receives: Drug: Caffeine (6mg/kg); Other: Placebo (Starch capsule) |
| Sequence ABAB | Experimental | Participants follow the sequence: Caffeine, Placebo, Caffeine, Placebo, with a 7-day washout period between sessions. Receives: Drug: Caffeine (6mg/kg); Other: Placebo (Starch capsule) |
| Sequence BABA | Experimental | Participants follow the sequence: Placebo, Caffeine, Placebo, Caffeine, with a 7-day washout period between sessions. Receives: Drug: Caffeine (6mg/kg); Other: Placebo (Starch capsule) |
What is being measured
The primary outcome is the main question the study is designed to answer.
Physical Work Capacity (total work in J)
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.
Measured: Measured during each laboratory exercise protocol (approximately 85-120 minutes).
Psychomotor Vigilance Test Reaction Time (ms)
Reaction time during the Psychomotor Vigilance Test expressed in milliseconds (ms).
Measured: 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).
Flanker Test Reaction Time (ms)
Reaction time during the Flanker Test expressed in milliseconds (ms).
Measured: 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).
Postural Control (mm)
Center of Pressure excursions measured using the BTrackS Balance Plate and expressed in millimeters (mm).
Measured: Measured continuously during the exercise protocol and at T1 (minute 2), T2 (minute 55), and T3 (minute 125).
Explosive power variables (mm)
Explosive lower-limb power expressed in millimeters (mm) - Countermovement Jump - height.
Measured: 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).
Secondary outcomes (50)
Exercise Heart Rate (bpm)
Heart rate expressed in beats per minute (bpm) recorded continuously throughout the standardized laboratory exercise protocol.
Measured: Measured continuously during each laboratory exercise protocol (approximately 85-120 minutes).
Exercise Heart Rate Variability (ms)
Heart rate variability expressed in milliseconds (ms) and recorded continuously throughout the standardized laboratory exercise protocol to assess autonomic regulation.
Measured: Measured continuously during each laboratory exercise protocol (approximately 85-120 minutes).
Salivary Cortisol Concentration (nmol/L)
Salivary cortisol concentration expressed in nmol/L.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before warm-up (60 minutes post-ingestion), 3 minutes post-exercise, and 10 minutes post-exercise.
Salivary Testosterone Concentration (pmol/L)
Salivary testosterone concentration expressed in pmol/L.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before warm-up (60 minutes post-ingestion), 3 minutes post-exercise, and 10 minutes post-exercise.
Salivary Alpha-amylase Activity (U/L)
Salivary alpha-amylase activity expressed in U/L.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before warm-up (60 minutes post-ingestion), 3 minutes post-exercise, and 10 minutes post-exercise.
Simple Reaction Time (ms)
Reaction time during the Simple Reaction Time test expressed in milliseconds (ms).
Measured: 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).
Heart Rate Recovery (bpm)
Heart rate recorded during the post-exercise recovery period, expressed in beats per minute (bpm).
Measured: Measured continuously during the first 5 minutes immediately following exercise cessation.
Rating of Perceived Exertion (Borg Scale, points)
Perceived exertion will be assessed using the Borg Rating of Perceived Exertion Scale and reported in points (6-20).
Measured: Before and immediately after warm-up, immediately after the Anaerobic Threshold phase, immediately after the Self-paced Maximal Time-trial, and immediately after cooldown during each laboratory study visit.
Personality Traits (NEO-FFI, points)
Personality traits will be assessed using the NEO Five-Factor Inventory (NEO-FFI). The questionnaire provides scores for five personality domains: Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness. Results will be reported as domain scores in points.
Measured: Measured at baseline (first study visit).
Mood State (POMS/BRUMS) (points)
Mood state assessed using the Profile of Mood States (POMS/BRUMS), expressed in points.
Measured: Measured during each laboratory study visit.
Caffeine Expectancy (Caff-EQ-Brief) (points)
Caffeine expectancy assessed using the Caffeine Expectancy Questionnaire-Brief (Caff-EQ-Brief), expressed in points.
Measured: Measured 30 minutes post-ingestion.
Urine pH
Urine pH measured using a urine strip analyzer.
Measured: Measured once prior to the start of each laboratory study visit.
White blood cells count and differential (count/L)
Assessment of the hematological parameter will be performed from fingertip capillary blood collected before supplementation (baseline), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
White blood cells count and differential (%)
Assessment of the hematological parameter will be performed from fingertip capillary blood collected before supplementation (baseline), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (red blood cells, RBC) (count/L)
Assessment of the hematological parameter will be performed from fingertip capillary blood collected before supplementation (baseline), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (hemoglobin concentration, HGB) (mmol/L)
Assessment of the hematological parameter will be performed from fingertip capillary blood collected before supplementation (baseline), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (hematocrit, HCT) (L/L)
Assessment of the hematological parameter will be performed from fingertip capillary blood collected before supplementation (baseline), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (mean corpuscular volume, MCV; mean platelet volume, MPV) (fL)
Assessment of the hematological parameter will be performed from fingertip capillary blood collected before supplementation (baseline), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (mean corpuscular hemoglobin mass, MCH) (fmol)
Assessment of the hematological parameter will be performed from fingertip capillary blood collected before supplementation (baseline), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (mean corpuscular hemoglobin concentration, MCHC) (mmol/L)
Assessment of the hematological parameter will be performed from fingertip capillary blood collected before supplementation (baseline), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (platelet count, PLT) (count/L)
Assessment of the hematological parameter will be performed from fingertip capillary blood collected before supplementation (baseline), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (platelet hematocrit, PCT) (cL/L)
Assessment of the hematological parameter will be performed from fingertip capillary blood collected before supplementation (baseline), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (platelet distribution width, PDW; platelet large cell ratio, PLCR; red blood cells distribution width - coefficient of variation, RDW-C) (%)
Assessment of the hematological parameter will be performed from fingertip capillary blood collected before supplementation (baseline), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (red blood cells distribution width - standard deviation, RDW-S) (fL)
Assessment of the hematological parameter will be performed from fingertip capillary blood collected before supplementation (baseline), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Urea Concentration (mmol/L)
Urea concentration measured from fingertip capillary blood and expressed in mmol/L.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Glucose Concentration (mg/dL)
Glucose concentration measured from fingertip capillary blood and expressed in mg/dL.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Creatinine concentration (μmol/L)
Creatinine concentration measured from fingertip capillary blood and expressed in µmol/L.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Muscle damage markers (activity of alanine aminotransferase, aspartate aminotransferase, creatine kinase, lactate dehydrogenase) (U/L)
Assessment of the muscle damage markers (activity of alanine aminotransferase, aspartate aminotransferase, creatine kinase, lactate dehydrogenase) (U/L) will be performed from fingertip capillary blood.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Lactate concentration (mmol/L)
Blood lactate concentration measured from fingertip capillary blood and expressed in mmol/L.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Electrolites' concentration (Ca, Na, K, Cl) (mmol/L)
Assessment of electrolites' concentration (Ca, Na, K, Cl) (mmol/L) will be performed from fingertip capillary blood.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Blood pH
Assessment of gasometry markers (blood pH) will be performed from fingertip capillary blood.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Partial Pressure of Carbon Dioxide and Oxygen (pCO2, pO2) (mmHg)
Assessment of gasometry markers (pCO2, pO2) (mmHg) will be performed from fingertip capillary blood.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
CAF and PAX concentrations (µmol/L)
Assessment of caffeine and paraxanthine concentrations (µmol/L) will be performed from fingertip capillary blood.
Measured: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Static weight distribution (mm)
Static weight distribution expressed in millimeters of Center of Pressure symmetry.
Measured: Measured at the start of each study visit.
Analysis of body composition (fat-free mass, fat mass) (kg)
Assessment of body composition (fat-free mass, fat mass) (kg) will be carried out at the start of each study visit.
Measured: Measured at the start of each study visit.
Analysis of body composition (total body water) (L)
Assessment of body composition (total body water) (L) will be carried out at the start of each study visit.
Measured: Measured at the start of each study visit.
Analysis of body composition (total body water) (%)
Assessment of body composition (total body water) (%) will be carried out at the start of each study visit.
Measured: Measured at the start of each study visit.
Autonomic Response during Cognitive Performance (bpm)
Heart rate and heart rate variability recording during cognitive testing blocks, expressed in beats per minute (bpm).
Measured: Measured at three time points: T1 (pre-ingestion; 2 minute of protocol), T2 (post-ingestion/pre-exercise; 55 minute of protocol), and T3 (post-exercise; 125 minute of protocol).
Anthropometric Indices (kg)
Body mass in kilograms will be measured at the start of each study visit.
Measured: Measured at the start of each study visit.
Anthropometric Indices (metres)
Height in metres will be measured at the start of each study visit.
Measured: Measured at the start of each study visit.
Explosive power variables (ms)
Explosive lower-limb power variables expressed in milliseconds (ms) - Countermovement Jump - contact time and flight time.
Measured: 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 power variables (W)
Explosive lower-limb power expressed in Watts (W) - Countermovement Jump - power.
Measured: 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).
Hydration Status (g/mL)
Assessment of urine specific gravity (g/mL) using a urine strip analyzer.
Measured: Once prior to the start of each laboratory study visit.
Flanker Test Accuracy (%)
Accuracy during the Flanker Test expressed as the percentage of correct responses.
Measured: 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).
Heart Rate Variability Recovery (ms)
Heart rate variability expressed in milliseconds (ms) during the post-exercise recovery period.
Measured: Measured continuously during the first 5 minutes immediately following exercise cessation.
Caffeine Expectancy Questionnaire Score (points)
Caffeine expectancy assessed using the Caffeine Expectancy Questionnaire and expressed in points.
Measured: Measured 30 minutes post-ingestion.
Suggestibility (SSS) (points)
General suggestibility assessed using the Short Suggestibility Scale (SSS), expressed in points.
Measured: Measured during the last study visit.
Intrinsic Motivation (IMI) (points)
Task-specific intrinsic motivation assessed using the Intrinsic Motivation Inventory (IMI), expressed in points.
Measured: Measured after each test block during every laboratory study visit.
Sport Motivation (SMS) (points)
Sport motivation assessed using the Sport Motivation Scale (SMS), expressed in points.
Measured: Measured during the first study visit.
Sleep Quality (LSEQ) (points)
Subjective sleep quality assessed using the Leeds Sleep Evaluation Questionnaire (LSEQ), expressed in points.
Measured: Measured once during each laboratory study visit.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted5 Aug 2026
- Study start1 Jan 2027 (estimated)
- Primary completion31 Mar 2028 (estimated)
- Study completion31 Mar 2029 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Physical PerformanceStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- Participants are divided into two MetaGroups (MG1 and MG2). MG1 follows a fully blinded crossover design (sequences AABB or BBAA), while MG2 follows a partially blinded mixed design (sequences ABAB or BABA), with all participants undergoing four experimental sessions separated by a 7-day washout period.
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 80 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Poznan University of Physical Education
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Jakub Malik, PhD, Principal investigator, Poznan University of Physical Education, Department of Sports Psychology
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07748429
- Sponsor's protocol ID
- 152-2-26
- Other IDs
- 2025/57/N/NZ4/04470
- Status last verified
- Jul 2026
- First submitted
- 21 Jul 2026
- Last updated
- 18 Sep 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: The study protocol will be published as an open-access article. Upon completion of the study, de-identified individual participant data (IPD) and relevant analytic code will be deposited in an open-access repository such as Zenodo or OSF, following the FAIR principles.
Study at a glance
From the registry record, last updated by the sponsor on 18 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Impact of Expectations on Physical Performance and Psychophysiological Potential: a Randomized, Double-blind, Placebo-controlled Crossover Study on the Placebo Effect in the Context of Caffeine Supplementation
- ClinicalTrials.gov ID
- NCT07748429
- Acronym / sponsor ID
- 152-2-26
- Conditions
- Physical Performance, Placebo Effect, Cognitive Performance
- Keywords
- Caffeine, Expectancy, Psychophysiology, Exercise PHysiology, Postural Control, Human Performance
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 80 participants (estimated)
- Lead sponsor
- Poznan University of Physical EducationUniversity, hospital or other
- Study start
- 1 Jan 2027 (estimated)
- Primary completion
- 31 Mar 2028 (estimated)
- Study completion
- 31 Mar 2029 (estimated)
- First posted
- 5 Aug 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Detailed description
This study employs a randomized, double-blind, placebo-controlled crossover design to conduct a multifactorial analysis of psychophysiological and biomechanical dynamics. Participants (n = 80, aged 20-35 years) will complete four experimental sessions separated by 7-day washout periods, involving caffeine (6 mg/kg) or placebo administration. The laboratory protocol (160 minutes) integrates multiple modalities: (1) cognitive testing (Reaction Time Test and Flanker Test), (2) postural control assessment using the BTrackS Balance Plate, and (3) a standardized cycle ergometer exercise protocol consisting of 15 minutes at the anaerobic threshold followed by a 5-minute self-paced maximal effort trial. Belief manipulation (immediate vs. retrospective reporting) and cognitive anchoring (feedback conditions) are implemented to isolate expectancy-driven effects. Continuous metabolic and cardiorespiratory data collected using the Cosmed K5 system will be synchronized with blood biomarkers (lactate, glucose, caffeine, and paraxanthine) and salivary biomarkers (cortisol, testosterone, and alpha-amylase). Advanced statistical methods, including Functional Data Analysis (FDA) and machine learning, will be used to integrate physiological trajectories with behavioral predictors.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 4
- Model description
- Participants are divided into two MetaGroups (MG1 and MG2). MG1 follows a fully blinded crossover design (sequences AABB or BBAA), while MG2 follows a partially blinded mixed design (sequences ABAB or BABA), with all participants undergoing four experimental sessions separated by a 7-day washout period.
| Arm | Type | Receives |
|---|---|---|
| Sequence AABB | Experimental | Drug: Caffeine (6mg/kg), Other: Placebo (Starch capsule)Participants follow the sequence: Caffeine, Caffeine, Placebo, Placebo, with a 7-day washout period between sessions. |
| Sequence BBAA | Experimental | Drug: Caffeine (6mg/kg), Other: Placebo (Starch capsule)Participants follow the sequence: Placebo, Placebo, Caffeine, Caffeine, with a 7-day washout period between sessions. |
| Sequence ABAB | Experimental | Drug: Caffeine (6mg/kg), Other: Placebo (Starch capsule)Participants follow the sequence: Caffeine, Placebo, Caffeine, Placebo, with a 7-day washout period between sessions. |
| Sequence BABA | Experimental | Drug: Caffeine (6mg/kg), Other: Placebo (Starch capsule)Participants follow the sequence: Placebo, Caffeine, Placebo, Caffeine, with a 7-day washout period between sessions. |
Who may qualify
- Ages
- 20 to 35 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (5 listed)
- Age between 20 and 35 years,
- Healthy adults,
- Regular physical activity, but not professional athletes,
- Normal or corrected-to-normal vision,
- Habitual caffeine consumption.
Key exclusion criteria (8 listed)
- 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,
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| 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. | Drug | Sequence AABB, Sequence ABAB, Sequence BABA, Sequence BBAA |
| Placebo (Starch capsule)Corn starch administered in an identical encapsulated form as the active caffeine, 60 minutes prior to the laboratory exercise protocol. | Other | Sequence AABB, Sequence ABAB, Sequence BABA, Sequence BBAA |
Primary outcome
Physical Work Capacity (total work in J)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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.
50 secondary outcomes
Exercise Heart Rate (bpm)
Time frame: Measured continuously during each laboratory exercise protocol (approximately 85-120 minutes).
Exercise Heart Rate Variability (ms)
Time frame: Measured continuously during each laboratory exercise protocol (approximately 85-120 minutes).
Salivary Cortisol Concentration (nmol/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before warm-up (60 minutes post-ingestion), 3 minutes post-exercise, and 10 minutes post-exercise.
Salivary Testosterone Concentration (pmol/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before warm-up (60 minutes post-ingestion), 3 minutes post-exercise, and 10 minutes post-exercise.
Salivary Alpha-amylase Activity (U/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before warm-up (60 minutes post-ingestion), 3 minutes post-exercise, and 10 minutes post-exercise.
Simple Reaction Time (ms)
Time frame: 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).
Heart Rate Recovery (bpm)
Time frame: Measured continuously during the first 5 minutes immediately following exercise cessation.
Rating of Perceived Exertion (Borg Scale, points)
Time frame: Before and immediately after warm-up, immediately after the Anaerobic Threshold phase, immediately after the Self-paced Maximal Time-trial, and immediately after cooldown during each laboratory study visit.
Personality Traits (NEO-FFI, points)
Time frame: Measured at baseline (first study visit).
Mood State (POMS/BRUMS) (points)
Time frame: Measured during each laboratory study visit.
Caffeine Expectancy (Caff-EQ-Brief) (points)
Time frame: Measured 30 minutes post-ingestion.
Urine pH
Time frame: Measured once prior to the start of each laboratory study visit.
White blood cells count and differential (count/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
White blood cells count and differential (%)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (red blood cells, RBC) (count/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (hemoglobin concentration, HGB) (mmol/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (hematocrit, HCT) (L/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (mean corpuscular volume, MCV; mean platelet volume, MPV) (fL)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (mean corpuscular hemoglobin mass, MCH) (fmol)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (mean corpuscular hemoglobin concentration, MCHC) (mmol/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (platelet count, PLT) (count/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (platelet hematocrit, PCT) (cL/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (platelet distribution width, PDW; platelet large cell ratio, PLCR; red blood cells distribution width - coefficient of variation, RDW-C) (%)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Hematological indices (red blood cells distribution width - standard deviation, RDW-S) (fL)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Urea Concentration (mmol/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Glucose Concentration (mg/dL)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Creatinine concentration (μmol/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Muscle damage markers (activity of alanine aminotransferase, aspartate aminotransferase, creatine kinase, lactate dehydrogenase) (U/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Lactate concentration (mmol/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Electrolites' concentration (Ca, Na, K, Cl) (mmol/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Blood pH
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Partial Pressure of Carbon Dioxide and Oxygen (pCO2, pO2) (mmHg)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
CAF and PAX concentrations (µmol/L)
Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.
Static weight distribution (mm)
Time frame: Measured at the start of each study visit.
Analysis of body composition (fat-free mass, fat mass) (kg)
Time frame: Measured at the start of each study visit.
Analysis of body composition (total body water) (L)
Time frame: Measured at the start of each study visit.
Analysis of body composition (total body water) (%)
Time frame: Measured at the start of each study visit.
Autonomic Response during Cognitive Performance (bpm)
Time frame: Measured at three time points: T1 (pre-ingestion; 2 minute of protocol), T2 (post-ingestion/pre-exercise; 55 minute of protocol), and T3 (post-exercise; 125 minute of protocol).
Anthropometric Indices (kg)
Time frame: Measured at the start of each study visit.
Anthropometric Indices (metres)
Time frame: Measured at the start of each study visit.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 18 Sep 2026.
- Individual participant dataSharing planned: Yes. The study protocol will be published as an open-access article. Upon completion of the study, de-identified individual participant data (IPD) and relevant analytic code will be deposited in an open-access repository such as Zenodo or OSF, following the FAIR principles.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Jakub Malik, PhD principal investigator
Poznan University of Physical Education, Department of Sports Psychology
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Caffeine (6mg/kg) in people with Physical Performance and Placebo Effect, run by Poznan University of Physical Education at 1 site in Poland.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 5 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 18 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Poland. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Jakub Malik, PhD (+48739975701, malik@awf.poznan.pl), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Physical Work Capacity (total work in J) (time frame: Measured during each laboratory exercise protocol (approximately 85-120 minutes).). The study lists 5 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 18 Sep 2026.