Acute Effects of Caffeine on Repeated Sprint Performance and Energy Distribution

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

Interventions

OTHER

Cycling Repeated Sprint Test (6 × 10 s)

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.

OTHER

Breath-by-Breath VO₂ Monitoring - COSMED K5

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).

OTHER

Capillary Blood Lactate Sampling (non-invasive)

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).

OTHER

Heart Rate Monitoring

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.

Sponsors & Collaborators

• Trabzon University

  lead OTHER

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

DOUBLE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

25 Years

Sex

MALE

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2025-04-15

Primary Completion

2025-05-30

Completion

2025-05-30

Countries

• Turkey (Türkiye)

Study Locations