The aim of this study is to evaluate the effects of omega-3 fatty acid supplementation on the Omega-3 Index, erythrocyte membrane composition, cognitive function, hormonal profile, speed, endurance performance, and hematological parameters in competitive athletes aged 16-35 years.
Skeletal muscle function, including the ability to generate force, sustain repeated high-intensity efforts, and resist fatigue, is essential for soccer performance. In addition to neuromuscular adaptations, increasing evidence suggests that nutritional interventions, particularly omega-3 fatty acid supplementation, may influence muscle function, recovery, inflammation, and cognitive performance. However, despite growing interest in omega-3 fatty acids, evidence regarding their effects on physical and cognitive performance in competitive soccer players remains limited. The present randomized, placebo-controlled trial aims to evaluate the effects of four weeks of high-dose omega-3 fatty acid supplementation in competitive male soccer players aged 16 to 35 years. Participants will continue their regular soccer training and maintain their habitual mixed diet throughout the study. The primary objective is to determine the effects of supplementation on the Omega-3 Index and the erythrocyte fatty acid profile, including omega-3, omega-6, trans fatty acids, and arachidonic acid (AA). In addition, the study will evaluate changes in cognitive function, hormonal profile, speed and endurance performance, hematological parameters, lipid profile, inflammatory markers, oxidative-antioxidant status, and erythrocyte membrane composition. The fatty acid profile will be assessed using a validated laboratory method that enables quantitative determination of individual fatty acids in erythrocyte membranes, providing an objective biomarker of long-term omega-3 status and membrane lipid composition. This approach allows comprehensive evaluation of the biological response to omega-3 supplementation in competitive athletes. The findings of this study are expected to improve understanding of the physiological effects of high-dose omega-3 fatty acid supplementation in soccer players and may contribute to evidence-based nutritional strategies aimed at optimizing health, recovery, cognitive function, and athletic performance.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
Participants will randomly assigned to the supplemented group. The supplement will be administered in a dose of 4 capsules twice a day for 4 weeks. Daily dose will contain 3500mg EPA + DHA
Participants will randomly assigned to the Placebo group. The placebo will be administered in a dose of 4 capsules twice a day for 4 weeks. Daily dose will contain 3500mg MCT.
Jerzy Kukuczka Academy of Physical Education in Katowice
Katowice, Mikolowska 72a, Poland
RECRUITINGChange in Omega Index
The Omega-3 Index will be assessed in erythrocytes as the combined percentage of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) relative to total fatty acids in erythrocyte membranes. Blood samples will be collected at baseline and after the 4-week supplementation period. In addition to the Omega-3 Index, the erythrocyte fatty acid profile, including individual omega-3 and omega-6 fatty acids, arachidonic acid (AA), and trans fatty acids, will be assessed. Changes from baseline to the end of the 4-week intervention will be evaluated.
Time frame: From enrollment to the end of 4-week supplementation
Neuromuscular function
Neuromuscular function was assessed using tensiomyography (TMG), a non-invasive method for evaluating the contractile properties of skeletal muscles. Parameters including contraction time (Tc), delay time (Td), sustain time (Ts), relaxation time (Tr), and maximal radial displacement (Dm) were measured at baseline and after the 4-week intervention.
Time frame: From enrollment to the end of supplementation period of 4 weeks
Hematological parameters and hormones
Hematological parameters were assessed using fasting venous blood samples. Outcome measures included complete blood count variables, including red blood cell count, white blood cell count, hemoglobin, hematocrit, platelet count, and red blood cell indices. Also testosteron and cortisol concentration was measured. Changes from baseline to the end of the 4-week intervention were evaluated.
Time frame: From enrollment to the end of supplementation period of 4 weeks
Lipoprteine profile
The lipoprotein profile was assessed using fasting blood samples. Outcome measures included total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglycerides. Changes from baseline to the end of the 4-week intervention were evaluated.
Time frame: From enrollment to the end of supplementation period of 4 weeks
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DIAGNOSTIC
Masking
DOUBLE
Enrollment
200
Cognitive function
Cognitive function was assessed using the Corsi Block-Tapping Test, which evaluates visuospatial working memory, short-term memory capacity, and executive cognitive performance. Changes in test performance were compared between baseline and the end of the 4-week intervention.
Time frame: From enrollment to the end of supplementation period of 4 weeks
Speed on 5 and 30m
Running times will be recorded using two pairs of dual-beam Witty Gate photocells (Microgate, Bolzano, Italy), a valid and reliable system for sprint performance assessment. Following a standardized warm-up, participants will perform two maximal 30-m sprint trials on an indoor artificial grass surface, with 15 minutes of passive recovery between trials. To prevent premature activation of the timing system, participants will start with the leading foot positioned 0.5 m behind the first timing gate. Split times at 5 m and 30 m will be recorded automatically, and the best performance from the two trials will be used for statistical analysis.
Time frame: From enrollment to the end of supplementation period of 4 weeks
Anaerobic performance
Anaerobic performance will be assessed using the Running-Based Anaerobic Sprint Test (RAST). Following a standardized warm-up, participants will perform six maximal 35-m sprints separated by 10 seconds of passive recovery. Sprint times will be recorded using an electronic timing system. Peak power, mean power, minimum power, fatigue index, and total sprint time will be calculated according to the standard RAST protocol. All tests will be performed under standardized environmental conditions, and participants will receive standardized verbal encouragement throughout the test.
Time frame: From enrollment to the end of supplementation period of 4 weeks
CMJ performance
Countermovement jump performance will be assessed using dual force plates (ForceDecks, VALD Performance, Australia), a validated system for quantifying vertical jump kinetics and kinematics. Before testing, participants will stand quietly on the force plates for 3 seconds to determine body mass and baseline force. The testing protocol will include bilateral countermovement jumps with arm swing (CMJa) and unilateral countermovement jumps performed separately on the dominant and non-dominant limbs. Participants will perform a rapid countermovement followed immediately by a maximal vertical jump. Three maximal trials will be completed for each test, with 1 minute of passive recovery between bilateral trials and 30 seconds between unilateral trials. The best trial for each test will be retained for analysis. Vertical ground reaction force data will be sampled at 1000 Hz and analyzed using the manufacturer's software. Outcome measures will incl
Time frame: From enrollment to the end of 4-week supplementation
Change in Reactive Strength and Leg Stiffness
Reactive strength and lower-limb stiffness will be assessed using the Myotest Pro system during three consecutive maximal plyometric jumps. Outcome measures will include reactive strength index (RSI) and leg stiffness. Changes from baseline to the end of the 4-week intervention will be evaluated.
Time frame: From enrollment to the end of 4-week supplementation