Combined Effects of Blueberry Supplementation and Football Training on Muscle Damage, Liver Enzymes, and Respiratory Function in Adolescent Athletes

Background: Blueberries contain bioactive compounds that may support exercise-related physiological adaptations. However, evidence regarding their effects on muscle damage, liver enzymes, and respiratory function in adolescent athletes is limited. This study investigated the effects of blueberry supplementation combined with football training on these parameters in adolescent football players. Methods: Thirty-six male adolescent players were randomly assigned to a control group (CG, n = 12), a blueberry supplementation group (EG, n = 12), or a blueberry supplementation plus additional exercise group (SEG, n = 12). All participants completed eight weeks of regular football training. The EG and SEG consumed 26 g/day of freeze-dried blueberry powder. Muscle damage and liver enzyme markers (CK, CK-MB, ALT, AST, LDH) and respiratory parameters (MIP, MEP, FVC, FEV₁, PEFmax, FEV₁/FVC) were assessed before and after the intervention. Results: No significant group × time effects were observed for muscle damage or liver enzyme markers (p > 0.05). In contrast, the SEG showed significant improvements in all respiratory parameters compared with the CG and EG (p < 0.05). Conclusion: Blueberry supplementation alone did not significantly affect muscle damage or liver enzyme responses in adolescent football players. When combined with structured football training and additional exercise, it may contribute to improved respiratory function and favorable functional adaptations.