Effects of L-Tyrosine and Caffeine on Performance in Elite Boxers (TYCAF-BOX)

Effects of L-Tyrosine and Caffeine Supplementation on Cognitive, Physical, and Physiological Parameters in Elite Boxers: A Randomized Double-Blind Placebo-Controlled Crossover Study

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.

Study Overview

• Status: Not yet recruiting
• Conditions: Sports Performance
• Intervention / Treatment: Dietary supplement: Placebo; Dietary supplement: L-Tyrosine; Dietary supplement: Caffeine; Dietary supplement: L-tyrosine + Caffeine

Detailed 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.

• Study Type: Interventional
• Enrollment (Estimated): 18
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Halil UÇAR; Phone Number: +90 5462921133; Email: halil.ucar@inonu.edu.tr

Study Locations

• Turkey (Türkiye)
  • Erzurum, Turkey (Türkiye)
    • Ataturk University Faculty of Sport Sciences
    • Contact: Halil UÇAR; Phone Number: +90 5462921133; Email: halil.ucar@inonu.edu.tr

Participation Criteria

Eligibility Criteria

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

Description

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

Study Plan

How is the study designed?

Design Details

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

Number of Arms

5

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Placebo Comparator: Placebo; Participants receive placebo condition.	Dietary supplement: Placebo; Placebo solution matched in taste and volume to active supplements.
Experimental: L-tyrosine; Participants receive L-tyrosine condition.	Dietary supplement: L-Tyrosine; L-tyrosine at 150 mg/kg body weight administered 60 minutes before exercise.
Experimental: Caffeine; Participants receive caffeine condition.	Dietary supplement: Caffeine; Caffeine at 5 mg/kg body weight administered 60 minutes before exercise.
Experimental: Combined; Participants receive combined supplementation condition.	Dietary supplement: L-tyrosine + Caffeine; Combined L-tyrosine (150 mg/kg) and caffeine (5 mg/kg) administered 60 minutes before exercise.
No Intervention: 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Stroop Test Performance	Cognitive performance assessed using the Stroop test, including reaction time and accuracy.	up to 12 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
BDNF Levels	Serum brain-derived neurotrophic factor levels measured before and after exercise.	up to 12 weeks
Oxidative Stress Markers	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.	up to 12 weeks

Collaborators and Investigators

• Sponsor: Inonu University
• Collaborators: Ataturk University

Study record dates

Study Major Dates

• Study Start (Estimated): September 1, 2026
• Primary Completion (Estimated): December 1, 2026
• Study Completion (Estimated): March 1, 2027

Study Registration Dates

• First Submitted: April 1, 2026
• First Submitted That Met QC Criteria: April 8, 2026
• First Posted (Actual): April 15, 2026

Study Record Updates

• Last Update Posted (Actual): July 8, 2026
• Last Update Submitted That Met QC Criteria: July 6, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Cognitive performance; BDNF; Caffeine; Anaerobic performance; L-tyrosine; Boxing
• Additional Relevant MeSH Terms: Amino Acids, Peptides, and Proteins; Heterocyclic Compounds; Heterocyclic Compounds, 2-Ring; Heterocyclic Compounds, Fused-Ring; Alkaloids; Purinones; Purines; Amino Acids; Amino Acids, Aromatic; Amino Acids, Cyclic; Xanthines; Caffeine; Tyrosine
• Other Study ID Numbers: UcarPhD2026

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

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