Caffeine, Cycling, Ergogenics, Exercise, Fat Metabolism
Conditions
Brief summary
The goal of this clinical trial is to learn if different forms of caffeine ingestion can influence fat oxidation during submaximal cycling exercise. The study will recruit healthy adults, both men and women, aged 18 to 50, who regularly perform aerobic exercise. The main questions it aims to answer are: * Does caffeine increase fat oxidation during one hour of cycling at the Fatmax intensity? * Do different forms of caffeine ingestion (capsule, coffee, chewing gum, or mouth rinse) differ in their effect on fat oxidation? * Do these caffeine forms alter total energy expenditure, cardiorespiratory response, or perceived exertion during exercise? * Are there differences in the occurrence or severity of side effects between caffeine administration methods? Researchers will compare each caffeine form to its corresponding placebo to determine their effects on fat oxidation and other physiological outcomes. Participants will: * Attend a pre-experimental session to determine their Fatmax intensity and VO₂max using an incremental cycling test * Perform eight experimental sessions, each consisting of one hour of cycling at Fatmax intensity * Receive caffeine or placebo via capsules, coffee, chewing gum, or mouth rinse according to a randomized, double-blind, crossover design * Be monitored for fat and carbohydrate oxidation, total energy expenditure, heart rate, and perceived exertion during exercise * Report any side effects immediately after the session and 24 hours later using a structured questionnaire All sessions will be conducted under controlled laboratory conditions with standardized protocols to ensure safety and reliable measurements.
Interventions
DRUGCaffeine (Guinama Anhydrous Powder)
3 mg/kg of anhydrous caffeine powder (Guinama, Spain) administered in an opaque capsule 60 min before exercise.
DIETARY_SUPPLEMENTCaffeine (Nescafé Classic Coffee)
3 mg/kg of caffeine via Nescafé Classic (Nestlé, Switzerland) dissolved in 250 mL of water 60 min before exercise.
DIETARY_SUPPLEMENTCaffeine (Kafewake Gum)
3 mg/kg of caffeine via Kafewake gum (Arafarma group, Spain), chewed for 10 min before exercise.
OTHERCaffeine Mouth Rinse Solution
3 mg/kg of caffeine (Nescafé Classic) dissolved in 25 mL of water for a 20-second rinse before exercise.
OTHERPlacebo (Cellulose Capsule)
Opaque capsule containing cellulose powder, matching caffeine capsules, taken 60 min before exercise.
OTHERPlacebo (Decaffeinated Coffee)
Decaffeinated Nescafé (Nestlé, Switzerland) in 250 mL of water, matching caffeinated coffee, taken 60 min before.
OTHERPlacebo (Non-caffeine Gum)
Kafewake Non-caffeinated gum (Arafarma group, Spain) with identical taste and texture, chewed for 10 min before.
OTHERPlacebo Mouth Rinse Solution
Decaffeinated Nescafé in 25 mL of water for a 20-second rinse immediately before exercise.
Sponsors
Universidad Rey Juan Carlos
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
DOUBLE (Subject, Investigator)
Intervention model description
Participants will undergo all experimental conditions (caffeine via capsule, coffee, chewing gum, and mouth rinse, and their corresponding placebos) in a randomized, double-blind, counterbalanced crossover design.
Eligibility
Sex/Gender
ALL
Age
18 Years to 50 Years
Healthy volunteers
Yes
Inclusion criteria
* Healthy men and women aged 18-50 years * Regular aerobic exercise at least 1 hour per day, 2 days per week * Provide written informed consent
Exclusion criteria
* Smoking * Use of medication or ergogenic supplements during the study period * Caffeine intolerance or allergy * Cardiopulmonary or musculoskeletal disorders * Use of oral contraceptives in female participants
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Rate of fat oxidation during submaximal cycling exercise at Fatmax intensity | 1 hour per experimental session | Continuous measurement of fat oxidation using indirect calorimetry during 1-hour cycling at Fatmax intensity. Calculated from respiratory gas exchange (VO₂ and VCO₂) using Frayn's equations. Unit of Measure: grams per minute (g/min). |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Rate of carbohydrate oxidation during submaximal cycling exercise at Fatmax intensity | 1 hour per experimental session | Continuous measurement of carbohydrate oxidation using indirect calorimetry during 1-hour cycling at Fatmax intensity. Calculated from respiratory gas exchange (VO₂ and VCO₂) using Frayn's equations. Unit of Measure: grams per minute (g/min). |
| Total energy expenditure during exercise | 1 hour per experimental session | Estimated from indirect calorimetry data using Brouwer's equation, recorded continuously during 1-hour cycling at Fatmax intensity. Unit of Measure: kilocalories per minute (kcal/min). |
| Mean Exercise Heart Rate | 1 hour per experimental session | Heart rate monitored continuously via a chest strap (Polar H9, Polar Electro, Findland) during the exercise test. Unit of Measure: beats per minute (bpm). |
| Oxygen consumption | 1 hour per experimental session | Volume of oxygen consumed during the exercise session measured breath-by-breath via indirect calorimetry using the Ergostik gas analyzer (Geratherm Respiratory GmbH, Germany). Unit of Measure: Liters per minute (L/min). |
| Carbon Dioxide Production | 1 hour per experimental session | Volume of carbon dioxide produced during the exercise session measured breath-by-breath via indirect calorimetry using the Ergostik gas analyzer (Geratherm Respiratory GmbH, Germany). Unit of Measure: Liters per minute (L/min). |
| Blood lactate concentration | Every 20 minutes during each 1-hour session | Measured from capillary blood samples taken from the fingertip during exercise to assess metabolic response to different caffeine interventions. Unit of measure: Millimoles per liter (mmol/L). |
| Rating of Perceived Exertion (RPE) during exercise | Every 10 minutes during each 1-hour session | Assessed using Borg's 6-20 scale; participants report perceived exertion at regular intervals. Unit of Measure: Units on a scale (from 6 to 20). |
| Occurrence of caffeine-related side effects | Immediately after each session and 24 hours post-exercise | Structured questionnaire assessing symptoms commonly associated with caffeine intake, such as nervousness, tremors, insomnia, gastrointestinal discomfort, and increased heart rate. |
Countries
Spain
Contacts
PRINCIPAL_INVESTIGATORJuan Del Coso, PhD
Universidad Rey Juan Carlos
PRINCIPAL_INVESTIGATORArturo Casado, PhD
Universidad Rey Juan Carlos
Outcome results
None listed