Effects of L-Tyrosine and Caffeine on Performance in Elite Boxers
Sports Performance
What this study involves
The registry does not currently label this study as recruiting. Ask about its status before planning a screening visit.
- Study type
- Interventional
- Phase
- Not applicable
- Age range
- 18 years - Not specified
- Sex eligible
- Male
- Healthy volunteers
- Accepted
- Participants
- 18 Estimated
These are starting points, not an eligibility decision. The research team must review the full requirements.
About the research
Participants will complete six sessions, including one familiarization and baseline session followed by five experimental conditions: control (no supplementation), placebo, L-tyrosine, caffeine, and combined L-tyrosine plus caffeine. The experimental conditions will be performed in a randomized, counterbalanced crossover design with a washout period of at least 72 hours between sessions. Resting physiological and cognitive assessments will be performed during the familiarization session, while biochemical, cognitive, and boxing-specific performance assessments will be conducted before and after each experimental session.
Read the full description
Participants will attend six sessions in total. The first session will be used for familiarization and baseline assessments, including anthropometric measurements, resting physiological measurements, and cognitive performance testing. The remaining five sessions will consist of one control condition (no supplementation) and four randomized experimental conditions (placebo, L-tyrosine, caffeine, and combined L-tyrosine plus caffeine) administered in a randomized, counterbalanced crossover design.
Each experimental session will be separated by a washout period of at least 72 hours. During the placebo, L-tyrosine, caffeine, and combined supplementation conditions, the assigned intervention will be administered 60 minutes before exercise. No supplement will be administered during the control condition.
Before and immediately after each experimental session, venous blood samples will be collected to assess brain-derived neurotrophic factor (BDNF) and oxidative stress biomarkers, including total antioxidant status (TAS), total oxidant status (TOS), malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GPx). Cognitive performance will be evaluated using the computerized Stroop test, and boxing-specific physical performance will be assessed using a standardized boxing simulation protocol. Heart rate and rating of perceived exertion (RPE) will also be recorded during the exercise protocol.
Who may be able to participate?
The list below is the sponsor’s full registry wording. It can include conditions, prior treatment, test results and other requirements. A match in search does not mean you qualify.
Inclusion Criteria:
Male elite boxers aged ≥18 years At least 8 years of boxing training experience Active participation in national or international competitions Regular training schedule No injury or illness affecting performance
Exclusion Criteria:
Use of nutritional supplements or stimulants within the last 4 weeks Any cardiovascular, metabolic, or neurological disorder Current injury or musculoskeletal limitation Smoking or excessive caffeine intake Failure to comply with study procedures
Understand screeningTreatment, groups and participation
The registry may describe treatments and study duration without a complete visit calendar. Ask the study team for the exact schedule, procedures, risks, costs and alternatives. Keep your usual care plan unless your treating clinician tells you otherwise.
- Assignment
- Random assignment
- Masking
- Double masked
Placebo
Participants receive placebo condition.
Dietary Supplement: Placebo
L-tyrosine
Participants receive L-tyrosine condition.
Dietary Supplement: L-Tyrosine
Caffeine
Participants receive caffeine condition.
Dietary Supplement: Caffeine
Combined
Participants receive combined supplementation condition.
Dietary Supplement: L-tyrosine + Caffeine
Control
Participants complete the experimental protocol without receiving placebo or active supplementation. Baseline cognitive, physiological, and physical performance assessments are performed under the control condition.
Placebo DIETARY_SUPPLEMENT
Placebo solution matched in taste and volume to active supplements.
L-Tyrosine DIETARY_SUPPLEMENT
L-tyrosine at 150 mg/kg body weight administered 60 minutes before exercise.
Caffeine DIETARY_SUPPLEMENT
Caffeine at 5 mg/kg body weight administered 60 minutes before exercise.
L-tyrosine + Caffeine DIETARY_SUPPLEMENT
Combined L-tyrosine (150 mg/kg) and caffeine (5 mg/kg) administered 60 minutes before exercise.
What researchers are measuring
Outcome measures describe what is being studied. They are not proof that a treatment works.
Primary measures
Stroop Test Performance
Time frame: up to 12 weeks
Cognitive performance assessed using the Stroop test, including reaction time and accuracy.
Secondary measures
BDNF Levels
Time frame: up to 12 weeks
Serum brain-derived neurotrophic factor levels measured before and after exercise.
Oxidative Stress Markers
Time frame: up to 12 weeks
Serum levels of total antioxidant status (TAS), total oxidant status (TOS), malondialdehyde (MDA), superoxide dismutase (SOD) activity, and glutathione peroxidase (GPx) activity will be measured.
Review the complete result tables and limitations in the official record.
Open official results ↗Research locations (1)
The overall study status and a local site’s status can differ. Confirm that location’s availability before traveling.
1 locations
Ataturk University Faculty of Sport SciencesErzurum, Turkey (Türkiye)Status unknown
Study team and timeline
- Lead sponsor
- Inonu University
- Study start
- Nov 15, 2026 Estimated
- Primary completion
- Jan 1, 2027 Estimated
- Study completion
- Jan 1, 2027 Estimated
- First posted
- Apr 15, 2026 Actual
- Last updated
- Nov 10, 2026 Actual
Official study contacts
Official study title
Effects of L-Tyrosine and Caffeine Supplementation on Cognitive, Physical, and Physiological Parameters in Elite Boxers: A Randomized Double-Blind Placebo-Controlled Crossover Study
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Source: ClinicalTrials.gov API v2. Information is submitted by sponsors and investigators. NLM does not approve the safety or science of all listed studies. Registry disclaimer.
Retrieved: Nov 12, 2026 · Last registry update: Nov 10, 2026