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.
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
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
Placebo solution matched in taste and volume to active supplements.
L-tyrosine at 150 mg/kg body weight administered 60 minutes before exercise.
Caffeine at 5 mg/kg body weight administered 60 minutes before exercise.
Ataturk University Faculty of Sport Sciences
Erzurum, Turkey (Türkiye)
Stroop Test Performance
Cognitive performance assessed using the Stroop test, including reaction time and accuracy.
Time frame: up to 12 weeks
BDNF Levels
Serum brain-derived neurotrophic factor levels measured before and after exercise.
Time frame: 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.
Time frame: up to 12 weeks
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DOUBLE
Enrollment
18
Combined L-tyrosine (150 mg/kg) and caffeine (5 mg/kg) administered 60 minutes before exercise.