Dose-dependent effects of apilarnil on muscle damage and endurance performance during exhaustive swimming exercise in rats: translational ınsights for sports physiology

Intensive exercise is known to induce muscle damage accompanied by excessive oxidative stress and inflammatory responses, which may compromise performance and recovery. Apilarnil, a nutrient-rich bee product containing bioactive phenolic compounds and flavonoids, has been proposed to exert antioxidant and anti-inflammatory effects; however, its role in exercise-induced physiological stress remains insufficiently characterized. Male Wistar rats were allocated into five groups: Control (CN), Without Exercise and Apilarnil (WEAP), Exercise (EX), Exercise + Apilarnil 0.2 g.kg−1 (EX + AP1), and Exercise + Apilarnil 0.4 g.kg−1 (EX + AP2). Exercised rats performed daily swimming (30 min/day) for 14 days, while apilarnil (0.2 or 0.4 g·kg−1) or vehicle was administered once daily throughout the 14-day protocol. An exhaustive swimming test was conducted at the end of the 14-day period, after which serum muscle damage markers, lipid peroxidation, pro-inflammatory cytokines, and antioxidant enzyme activities were assessed in skeletal and cardiac muscle tissues. Compared with WEAP, exhaustive swimming increased muscle damage markers, lipid peroxidation, and inflammatory cytokine levels. Compared with EX, apilarnil supplementation attenuated oxidative and inflammatory responses and enhanced endogenous antioxidant enzyme activities. Notably, the lower apilarnil dose resulted in the greatest improvement in swimming performance, whereas performance benefits were attenuated at the higher dose despite favorable biochemical profiles. Apilarnil supplementation modulated exercise-induced oxidative stress and inflammatory responses in skeletal and cardiac muscle tissues, with dose-dependent effects observed primarily in biochemical markers. In contrast, endurance performance follows a non-linear pattern, peaking at the lower dose and diminishing at the higher dose, underscoring the need to identify an optimal ergogenic dose.