Effects of L-Tyrosine and Caffeine on Performance in Elite Boxers

NCT07530185 — Not applicable, Not yet recruiting, 18 participants, Inonu University

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

Registry	NCT07530185, acronym TYCAF-BOX
Status	Not yet recruiting
Phase	Not applicable
Study type	Interventional; randomized, crossover, masking: double, basic science
Enrollment	18 (Estimated)
Sponsor	Inonu University (Other); collaborators: Ataturk University
Conditions	Sports Performance
Interventions	Placebo, L-Tyrosine, Caffeine, L-tyrosine + Caffeine (Dietary supplement)
Dates	start 2026-09-01 (estimated), primary completion 2026-12-01 (estimated), completion 2027-03-01 (estimated), first posted 2026-04-15, last updated 2026-07-08
Locations	1 site in Turkey (Türkiye)

-Summary

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.

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+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.

+Arms and interventions

Arm	Type	Interventions	Description
Placebo	Placebo comparator	Dietary Supplement: Placebo	Participants receive placebo condition.
L-tyrosine	Experimental	Dietary Supplement: L-Tyrosine	Participants receive L-tyrosine condition.
Caffeine	Experimental	Dietary Supplement: Caffeine	Participants receive caffeine condition.
Combined	Experimental	Dietary Supplement: L-tyrosine + Caffeine	Participants receive combined supplementation condition.
Control	No intervention		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.

+Outcome measures

Primary outcomes

Stroop Test Performance [up to 12 weeks]: Cognitive performance assessed using the Stroop test, including reaction time and accuracy.

Secondary outcomes

BDNF Levels [up to 12 weeks]: Serum brain-derived neurotrophic factor levels measured before and after exercise.
Oxidative Stress Markers [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.

+Eligibility

Sex: Male, ages: 18 Years to any, accepts healthy volunteers

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

+Locations (1)

Facility	City	Country	Status
Ataturk University Faculty of Sport Sciences	Erzurum	Turkey (Türkiye)