Acute and Long-Term Inflammatory Responses in Well-Trained Young Swimmers throughout a Training Season

Abstract

Background: The immunological responses to exercise and the corresponding adaptations in high-level sports have become an important issue, from both the health and the physical performance points of view. A better understanding of the immune responses to exercise and chronic exercise training may benefit athletes and improve physical performance and health. The purpose of this study was to investigate the fluctuations in the immune status of young swimmers throughout a training season. Methods: Twelve well-trained male swimmers (14.08 ± 1.0 yrs) were recruited. Measurements were carried out at the beginning of the training season (T1) and pre- and post the taper of each competitive period (i.e., T2, T3 for the first training macrocycle, and T4, T5 for the second macrocycle, respectively). Blood samples were collected before and 1 hour post a maximal 400 m swimming testing at each of the above time points. Serum interleukin (IL)-1β, IL-6, IL-1rα, IL-4, IL-10, C-reactive protein (CRP) and creatine kinase (CK) levels were measured. Adjustment for exercise-induced plasma volume changes was performed before all data analyses. Two-way analysis of variance (ANOVA) with repeated measures was used for statistics. Results: An anti-inflammatory profile was induced during the second competitive period characterized by a reduction in the levels of inflammatory indices (T1 compared to T4 and T5, IL-1β: p = 0.019, p = 0.034 respectively; T1 compared to T4, CRP: –43%, p > 0.05) along with a tendency of increase in anti-inflammatory ones (T1–T5, IL-6: 75%, T4–T5 IL-10: 122%; p > 0.05). Moreover, acute exercise induced anti-inflammatory responses, causing an increase in anti-inflammatory cytokines (IL-6, IL-10, IL-1rα; p < 0.05). There was a significant decrease in serum CK levels between T1-T4 both in the pre- and post-test condition (p = 0.027, p = 0.005, respectively), while significant differences were found between pre- and post-test at T1, T2, and T4 (p = 0.000, p = 0.011, p = 0.017, respectively). Conclusions: The findings of this study indicated that swimming training throughout a season induces mild long-term but strong acute effects on the immune profile of the swimmers. These findings should be taken into consideration throughout a training season in young swimmers, adjusting the exercise stimuli accordingly in terms of volume, intensity, and recovery time.