Acute Effects of Caffeine on Repeated Sprint Performance and Energy Distribution

NCT07596511 | Completed

• 1 other identifier: E-69268593-050.04-25025
• Study Type: interventional
• Target: 15
• Locations: 1 country
• Sites: 1

Brief Summary

The goal of this study is to learn if low-dose caffeinated coffee improves repeated sprint performance and affects energy system contributions in combat sports athletes. The main questions it aims to answer are:

• Does low-dose caffeinated coffee (1.5 or 3 mg·kg-¹) improve peak power, mean power, and fatigue index during repeated sprint tests?
• What physiological responses (heart rate, blood lactate, perceived exertion, and energy system contributions) do participants have when consuming caffeinated coffee? Researchers compared caffeinated coffee at two doses (1.5 and 3 mg·kg-¹ body mass) to a placebo (decaffeinated coffee of identical taste and appearance) to see if low

Conditions

Healthy Adult Male

Keywords

basic science

Outcome Measures

Primary Outcomes (3)

• Peak Power Output

  Highest instantaneous power output (Watts) recorded across all six 10-second sprint bouts on the cycle ergometer (Monark 894E), with resistance set at 10% of body mass.

  On 3 testing days with 48-hour interval

• Mean Power Output

  Average power output (Watts) calculated across all six sprint efforts, reflecting the athlete's overall capacity to sustain high-intensity output across the full protocol.

  On 3 testing days with 48-hour interval

• Fatigue Index

  Quantified as: FI = 100 × (1 - total peak power / ideal peak power), where ideal peak power is the product of the highest single-sprint peak power and the total number of repetitions. Expressed as a percentage (%).

  On 3 testing days with 48-hour interval

Secondary Outcomes (7)

• Total Energy Expenditure

  On 3 testing days with 48-hour interval

• Energy System - Oxidative Contribution

  On 3 testing days with 48-hour interval

• Energy System - ATP Contribution

  On 3 testing days with 48-hour interval

• Energy System - Glycolytic Contribution

  On 3 testing days with 48-hour interval

• Peak Heart Rate

  On 3 testing days with 48-hour interval

Study Arms (3)

Placebo

PLACEBO COMPARATOR

Participants ingested decaffeinated coffee (Nescafe Gold, decaffeinated) at a dose equivalent to 3 mg·kg-¹ of body mass, dissolved in 250 mL of hot water and consumed over 10 minutes, administered 60 minutes before the exercise test.

Other: Cycling Repeated Sprint Test (6 × 10 s); Other: Breath-by-Breath VO₂ Monitoring - COSMED K5; Other: Capillary Blood Lactate Sampling (non-invasive); Other: Heart Rate Monitoring

Low-Dose Caffeine - 1.5 mg·kg-¹

EXPERIMENTAL

A blended preparation of caffeinated and decaffeinated (for the similar taste of intensity with 3 mg/kg intervention) Nescafe Gold coffee dissolved in 250 ml hot water was administered at a total dose corresponding to 1.5 mg·kg-¹ body mass of caffeine. Volume was equalized to the placebo condition through addition of decaffeinated coffee.

Other: Cycling Repeated Sprint Test (6 × 10 s); Other: Breath-by-Breath VO₂ Monitoring - COSMED K5; Other: Capillary Blood Lactate Sampling (non-invasive); Other: Heart Rate Monitoring

Low-Dose Caffeine - 3 mg·kg-¹

EXPERIMENTAL

Regular caffeinated Nescafe Gold coffee dissolved in 250 ml hot water was administered at a dose delivering 3 mg·kg-¹ body mass of caffeine.

Other: Cycling Repeated Sprint Test (6 × 10 s); Other: Breath-by-Breath VO₂ Monitoring - COSMED K5; Other: Capillary Blood Lactate Sampling (non-invasive); Other: Heart Rate Monitoring

Interventions

Cycling Repeated Sprint Test (6 × 10 s) OTHER

A standardized cycling-based repeated sprint protocol consisting of six 10-second maximal-effort sprints, each separated by a 30-second passive rest interval, performed on a mechanically braked cycle ergometer (Monark 894E, Vansbro, Sweden). Resistance was calibrated at 10% of the participant's individual body mass. The inertial momentum of the flywheel was excluded from power output calculations following the approach described by Bogdanis et al. (2008). Each session was preceded by a structured warm-up consisting of five 30-second bouts at 100 W, followed by a 5-minute seated rest before test commencement. Each participant initiated the protocol with their dominant leg to ensure procedural consistency across all sessions.

Low-Dose Caffeine - 1.5 mg·kg-¹; Low-Dose Caffeine - 3 mg·kg-¹; Placebo

Breath-by-Breath VO₂ Monitoring - COSMED K5 OTHER

Continuous breath-by-breath oxygen uptake (VO₂) data were collected throughout each testing session using the COSMED K5 portable metabolic system (Rome, Italy). Data were used to estimate the relative and absolute contributions of the three metabolic energy pathways. The fast component of excess post-exercise oxygen consumption (EPOC) was extracted and modeled using a mono-exponential function (OriginPro 8.0, OriginLab Corp.) to estimate phosphocreatine (PCr) resynthesis during recovery intervals and following the final sprint. Oxidative metabolism contribution was derived by subtracting resting VO₂ from exercise VO₂. Total energy demand was expressed in both liters of O₂ and kilojoules (caloric equivalent: 20.92 kJ·L-¹ O₂).

Low-Dose Caffeine - 1.5 mg·kg-¹; Low-Dose Caffeine - 3 mg·kg-¹; Placebo

Capillary Blood Lactate Sampling (non-invasive) OTHER

Capillary blood samples were obtained at two time points per session: (1) resting lactate (LA\_rest) - collected following a 20-minute passive rest period immediately before the sprint test, in accordance with published lactate clearance protocols; and (2) maximal post-exercise lactate (LA\_max) - collected immediately upon completion of the final sprint repetition. Delta lactate (ΔLA) was calculated as the arithmetic difference between LA\_max and LA\_rest and expressed in mmol·L-¹. Delta lactate values were additionally used to estimate the glycolytic energy system contribution, applying a conversion factor of 3 mL O₂·kg-¹ body mass per 1 mmol·L-¹ increase in blood lactate concentration (Di Prampero \& Ferretti, 1999).

Low-Dose Caffeine - 1.5 mg·kg-¹; Low-Dose Caffeine - 3 mg·kg-¹; Placebo

Heart Rate Monitoring OTHER

Continuous heart rate was recorded throughout each testing session via chest type radiotelemetry sensor integrated with COSMED K5. Peak heart rate (HR\_peak, bpm) was defined as the highest value observed across the entire repeated sprint protocol and reported as a secondary physiological outcome.

Low-Dose Caffeine - 1.5 mg·kg-¹; Low-Dose Caffeine - 3 mg·kg-¹; Placebo

Eligibility Criteria

• Age: 18 Years - 25 Years
• Sex: male
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Male combat sports athletes aged 18 to 25 years
• Minimum of five years of continuous structured training
• Competitive experience at both regional (state) and national levels
• Willingness to abstain from all caffeinated products for two weeks prior to and throughout the study period
• Ability to follow a standardized dietary protocol prescribed by an Olympic Preparation Center dietitian
• Provision of written informed consent

You may not qualify if:

• Age below 18 years
• Self-reported use of anabolic agents, hormonal modulators, or performance-influencing dietary supplements within the three months preceding enrollment
• Current use of narcotic, psychotropic, stimulant medications, or tobacco products during the assessment period
• Presence of any diagnosed medical condition (including cardiovascular, metabolic, neurological, respiratory, or musculoskeletal disorders) that may compromise safe participation
• Withdrawal from the study at the participant's own request

Sponsors & Collaborators

• Trabzon University: lead

Study Sites (1)

Trabzon University Faculty of Sport Sciences

Trabzon, Akçaabat, 61300, Turkey (Türkiye)

Location

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, INVESTIGATOR
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Assisstant Professor - PHD

Study Record Dates

• First Submitted: May 12, 2026
• First Posted: May 19, 2026
• Study Start: April 15, 2025
• Primary Completion: May 30, 2025
• Study Completion: May 30, 2025
• Last Updated: May 19, 2026

Record last verified: 2026-05

Data Sharing

• IPD Sharing: Will not share

Locations

TU (1)