Oxidative stress and hematological alterations without a cortisol response to exercise in young swimmers during the luteal phase

Physiological response to exercise in young female athletes is understudied, especially regarding how the luteal phase of the menstrual cycle influences performance in demanding sports such as swimming. Therefore, this study aimed to evaluate the post-exercise hormonal response, oxidative stress markers, and hematological parameters following a moderate-intensity exercise test in trained adolescent female swimmers. Eighteen swimmers (aged 12-16 years) performed a swimming test (800m + 200m + 50m) during their rigorously verified luteal phase. Blood samples were collected before exercise, immediately after exercise, and after 3 hours of recovery. Moderate-intensity exercise significantly increased 8-isoprostane levels, while cortisol and 4-hydroxynonenal levels showed no significant changes. Microscopic blood smear analysis showed erythrocyte anisocytosis and poikilocytosis, toxic granulation in granulocytes, and activated lymphocytes. These findings suggest that young swimmers are more prone to exercise-induced oxidative stress, likely due to an immature antioxidant system. The disconnect between stable cortisol levels and elevated 8-isoprostanes highlights a complex relationship between endocrine and redox factors. Our results underscore the importance of considering the menstrual cycle for health monitoring and the accurate training planning for young female athletes.