Acute Effects of Caffeine on Repeated Sprint Performance and Energy Distribution

Acute Effect of Caffeinated and Decaffeinated Coffee Consumption on Repeated Sprint Performance and Energy Contribution Distribution

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

Study Overview

• Status: Completed
• Conditions: Healthy Adult Male
• Intervention / Treatment: 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

Detailed Description

This investigation examined whether acute ingestion of low-dose caffeine delivered through commercially available regular coffee would alter repeated sprint capacity and metabolic energy system dynamics in athletes who compete in combat disciplines. A within-subject, double-blind, placebo-controlled crossover framework was adopted to ensure methodological rigor and minimize order and expectation biases. Eligible participants were physically active male combat sports competitors (n = 15; aged 18-25 years) with a documented competitive history spanning at least five years at the regional and national levels. Volunteers were excluded if they reported recent use of performance-modifying agents, stimulant or psychotropic medications, tobacco products, or any diagnosed condition affecting cardiovascular, metabolic, or musculoskeletal function. To standardize caffeine baseline, all participants were instructed to abstain from caffeinated products for a minimum of two weeks prior to the study onset and throughout the entire data collection period.

Each participant attended the laboratory on four separate occasions. The initial visit served as a familiarization session and included anthropometric assessment. The subsequent three sessions were assigned in a randomized, counterbalanced order, with a minimum 48-hour recovery interval separating each visit. During these sessions, participants received one of three coded supplementation conditions - placebo (decaffeinated coffee), low-dose caffeine (1.5 mg·kg-¹ body mass), or moderate-low-dose caffeine (3 mg·kg-¹ body mass) - each dissolved in 250 mL of hot water and consumed over a 10-minute period. The caffeine content of both the caffeinated and decaffeinated coffee products (Nescafe Gold) was verified by an accredited food analysis laboratory. To maintain identical volume, appearance, and taste across all conditions, decaffeinated and caffeinated coffees were blended in varying proportions for each dose level. Supplementation was administered 60 minutes before the commencement of exercise testing. Performance testing comprised a standardized cycling-based repeated sprint protocol: six 10-second maximal effort sprints, each separated by a 30-second passive recovery period, performed on a mechanically braked cycle ergometer (Monark 894E) with resistance set at 10% of individual body mass. A structured warm-up preceded each testing bout. Primary performance variables derived from sprint testing included peak power output, mean power output, and fatigue index. Perceptual and physiological responses were documented via the Borg rating of perceived exertion scale, peak heart rate, and capillary blood lactate concentration measured at rest and immediately following the final sprint. Breath-by-breath oxygen uptake data were collected continuously using a portable metabolic system (COSMED K5) to facilitate estimation of energy system contributions. The relative and absolute contributions of the phosphocreatine (ATP-PCr), glycolytic, and oxidative metabolic pathways were quantified using established indirect methods. Excess post-exercise oxygen consumption (EPOC) kinetics were modeled with mono-exponential curve fitting to isolate the fast EPOC component, which served as a proxy for PCr resynthesis. Glycolytic contribution was estimated from the net change in blood lactate concentration, applying an established oxygen-equivalent conversion factor. Oxidative metabolism was derived from the net elevation in VO₂ above resting values during exercise. Total energy expenditure was computed as the cumulative sum of all three pathway contributions. To control for dietary and diurnal confounders, participants replicated identical pre-test meal patterns documented during the first testing session, and all laboratory visits were conducted between 08:00 and 11:00 h. Dietary adherence was verified through structured diet logs reviewed by the research team. Data were analyzed using one-way repeated-measures ANOVA with Bonferroni-adjusted pairwise comparisons, and partial eta squared (η²p) was reported as the measure of effect magnitude. The study received full ethical clearance from the Trabzon Eurasia University Ethics Committee and was conducted in accordance with the principles outlined in the Declaration of Helsinki. Informed consent form obtained from all the participants.

• Study Type: Interventional
• Enrollment (Actual): 15
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Akçaabat
    • Trabzon, Akçaabat, Turkey (Türkiye), 61300
      • Trabzon University Faculty of Sport Sciences

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• 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

Exclusion Criteria:

• 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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Double

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Placebo Comparator: Placebo; 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); 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.
Experimental: Low-Dose Caffeine - 1.5 mg·kg-¹; 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); 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.
Experimental: Low-Dose Caffeine - 3 mg·kg-¹; 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); 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
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 Outcome Measures

Outcome Measure	Measure Description	Time Frame
Total Energy Expenditure	Computed as the cumulative sum of ATP-PCr, glycolytic, and oxidative pathway contributions, expressed in kilojoules (kJ), using a caloric equivalent of 20.92 kJ per liter of O₂ consumed.	On 3 testing days with 48-hour interval
Energy System - Oxidative Contribution	Estimated absolute contributions (kJ) of each metabolic pathway. Oxidative contribution calculated as net VO₂ elevation above resting baseline. Breath-by-breath VO₂ data collected continuously via COSMED K5 portable metabolic system.	On 3 testing days with 48-hour interval
Energy System - ATP Contribution	ATP-PCr contribution derived from the fast component of EPOC kinetics modeled via mono-exponential curve fitting (OriginPro 8.0).	On 3 testing days with 48-hour interval
Energy System - Glycolytic Contribution	Glycolytic contribution estimated from net blood lactate rise (3 mL O₂·kg-¹ per 1 mmol·L-¹ increase).	On 3 testing days with 48-hour interval
Peak Heart Rate	Highest recorded heart rate (bpm) during the repeated sprint test.	On 3 testing days with 48-hour interval
Delta Blood Lactate Concentration	Difference between resting capillary blood lactate (measured after 20-minute passive rest prior to testing) and maximum post-exercise lactate (measured immediately following the final sprint). Expressed in mmol·L-¹.	On 3 testing days with 48-hour interval
Rating of Perceived Exertion	Subjective effort rating collected using the Borg scale (6-20) following the completion of the repeated sprint protocol.	On 3 testing days with 48-hour interval

Collaborators and Investigators

• Sponsor: Trabzon University

Study record dates

Study Major Dates

• Study Start (Actual): April 15, 2025
• Primary Completion (Actual): May 30, 2025
• Study Completion (Actual): May 30, 2025

Study Registration Dates

• First Submitted: May 12, 2026
• First Submitted That Met QC Criteria: May 18, 2026
• First Posted (Actual): May 19, 2026

Study Record Updates

• Last Update Posted (Actual): May 19, 2026
• Last Update Submitted That Met QC Criteria: May 18, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: basic science
• Other Study ID Numbers: E-69268593-050.04-25025

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: All the data collected in this study anonymized and only will be used in the scope of academic paper publication.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No