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NCT Number: NCT07748429

Placebo Effect on Cycling Performance: Laboratory Crossover Study

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.

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Key information

Conditions

Physical Performance Cognitive Performance Placebo Effect

Age range

20 year–30 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

About this study

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.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Age between 20 and 30 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.

Treatment and study plan

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.

Primary outcomes

  1. 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.

Secondary outcomes

  1. Exercise Heart Rate (bpm)

    Time frame: Measured continuously during each laboratory exercise protocol (approximately 85-120 minutes).

    Heart rate expressed in beats per minute (bpm) recorded continuously throughout the standardized laboratory exercise protocol.

  2. Exercise Heart Rate Variability (ms)

    Time frame: Measured continuously during each laboratory exercise protocol (approximately 85-120 minutes).

    Heart rate variability expressed in milliseconds (ms) and recorded continuously throughout the standardized laboratory exercise protocol to assess autonomic regulation.

  3. Salivary Cortisol Concentration (nmol/L)

    Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, after warm-up (60 minutes post-ingestion), and 3 minutes post-exercise.

    Salivary cortisol concentration expressed in nmol/L.

  4. Salivary Testosterone Concentration (pmol/L)

    Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, after warm-up (60 minutes post-ingestion), and 3 minutes post-exercise.

    Salivary testosterone concentration expressed in pmol/L.

  5. Salivary Alpha-amylase Activity (U/L)

    Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, after warm-up (60 minutes post-ingestion), and 3 minutes post-exercise.

    Salivary alpha-amylase activity expressed in U/L.

  6. 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).

    Reaction time during the Simple Reaction Time test expressed in milliseconds (ms).

  7. Heart Rate Recovery (bpm)

    Time frame: Measured continuously during the first 5 minutes immediately following exercise cessation.

    Heart rate recorded during the post-exercise recovery period, expressed in beats per minute (bpm).

  8. 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).

  9. 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.

    Perceived exertion will be assessed using the Borg Rating of Perceived Exertion Scale and reported in points (6-20).

  10. Personality Traits (NEO-FFI, points)

    Time frame: Measured at baseline (first study visit).

    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.

  11. Mood State (POMS/BRUMS) (points)

    Time frame: Measured during each laboratory study visit.

    Mood state assessed using the Profile of Mood States (POMS/BRUMS), expressed in points.

  12. Caffeine Expectancy (Caff-EQ-Brief) (points)

    Time frame: Measured 30 minutes post-ingestion.

    Caffeine expectancy assessed using the Caffeine Expectancy Questionnaire-Brief (Caff-EQ-Brief), expressed in points.

  13. Urine pH

    Time frame: Measured once prior to the start of each laboratory study visit.

    Urine pH measured using a urine strip analyzer.

  14. 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.

    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.

  15. White blood cells count and differential (%)

    Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.

    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.

  16. 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.

    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.

  17. 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.

    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.

  18. Hematological indices (hematocrit, HCT) (L/L)

    Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.

    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.

  19. 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.

    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.

  20. 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.

    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.

  21. 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.

    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.

  22. 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.

    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.

  23. 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.

    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.

  24. 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.

    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.

  25. 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.

    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.

  26. Urea Concentration (mmol/L)

    Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.

    Urea concentration measured from fingertip capillary blood and expressed in mmol/L.

  27. Glucose Concentration (mg/dL)

    Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.

    Glucose concentration measured from fingertip capillary blood and expressed in mg/dL.

  28. Creatinine concentration (μmol/L)

    Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.

    Creatinine concentration measured from fingertip capillary blood and expressed in µmol/L.

  29. 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.

    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.

  30. Lactate concentration (mmol/L)

    Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.

    Blood lactate concentration measured from fingertip capillary blood and expressed in mmol/L.

  31. 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.

    Assessment of electrolites' concentration (Ca, Na, K, Cl) (mmol/L) will be performed from fingertip capillary blood.

  32. Blood pH

    Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.

    Assessment of gasometry markers (blood pH) will be performed from fingertip capillary blood.

  33. 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.

    Assessment of gasometry markers (pCO2, pO2) (mmHg) will be performed from fingertip capillary blood.

  34. CAF and PAX concentrations (µmol/L)

    Time frame: Measured at baseline (pre-supplementation), 30 minutes post-ingestion, before exercise, and 3 minutes post-exercise.

    Assessment of caffeine and paraxanthine concentrations (µmol/L) will be performed from fingertip capillary blood.

  35. Static weight distribution (mm)

    Time frame: Measured at the start of each study visit.

    Static weight distribution expressed in millimeters of Center of Pressure symmetry.

  36. Analysis of body composition (fat-free mass, fat mass) (kg)

    Time frame: Measured at the start of each study visit.

    Assessment of body composition (fat-free mass, fat mass) (kg) will be carried out at the start of each study visit.

  37. Analysis of body composition (total body water) (L)

    Time frame: Measured at the start of each study visit.

    Assessment of body composition (total body water) (L) will be carried out at the start of each study visit.

  38. Analysis of body composition (total body water) (%)

    Time frame: Measured at the start of each study visit.

    Assessment of body composition (total body water) (%) will be carried out at the start of each study visit.

  39. 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).

    Heart rate and heart rate variability recording during cognitive testing blocks, expressed in beats per minute (bpm).

  40. Anthropometric Indices (kg)

    Time frame: Measured at the start of each study visit.

    Body mass in kilograms will be measured at the start of each study visit.

  41. Anthropometric Indices (metres)

    Time frame: Measured at the start of each study visit.

    Height in metres will be measured at the start of each study visit.

  42. Explosive power variables (ms)

    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 variables expressed in milliseconds (ms) - Countermovement Jump - contact time and flight time.

  43. Explosive power variables (W)

    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 Watts (W) - Countermovement Jump - power.

  44. 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.

  45. Hydration Status (g/mL)

    Time frame: Once prior to the start of each laboratory study visit.

    Assessment of urine specific gravity (g/mL) using a urine strip analyzer.

  46. 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).

  47. 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).

  48. Flanker Test Accuracy (%)

    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).

    Accuracy during the Flanker Test expressed as the percentage of correct responses.

  49. Heart Rate Variability Recovery (ms)

    Time frame: Measured continuously during the first 5 minutes immediately following exercise cessation.

    Heart rate variability expressed in milliseconds (ms) during the post-exercise recovery period.

  50. Caffeine Expectancy Questionnaire Score (points)

    Time frame: Measured 30 minutes post-ingestion.

    Caffeine expectancy assessed using the Caffeine Expectancy Questionnaire and expressed in points.

  51. Suggestibility (SSS) (points)

    Time frame: Measured during the last study visit.

    General suggestibility assessed using the Short Suggestibility Scale (SSS), expressed in points.

  52. Intrinsic Motivation (IMI) (points)

    Time frame: Measured after each test block during every laboratory study visit.

    Task-specific intrinsic motivation assessed using the Intrinsic Motivation Inventory (IMI), expressed in points.

  53. Sport Motivation (SMS) (points)

    Time frame: Measured during the first study visit.

    Sport motivation assessed using the Sport Motivation Scale (SMS), expressed in points.

  54. Sleep Quality (LSEQ) (points)

    Time frame: Measured once during each laboratory study visit.

    Subjective sleep quality assessed using the Leeds Sleep Evaluation Questionnaire (LSEQ), expressed in points.

Study contacts

Contact information is provided by the study sponsor or research team.

Jakub Malik, PhD

CONTACT

[email protected]

+48739975701

Sponsors and collaborators

Lead sponsor

Poznan University of Physical Education

Other

Registry information

Official study 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

Important dates

Study start
2026
Primary completion
2028
Study completion
2029
First posted
Aug 5, 2026
Registry last updated
Aug 5, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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