Long-term swimming training modifies acute immune cell response to a high-intensity session

Area of Science:

• Exercise immunology
• Sports science
• Athlete health

Background:

• Long-term training effects on athletes' immune responses to acute exercise are understudied.
• Both chronic training and acute exercise induce complex immune adaptations.
• Understanding these adaptations is crucial for optimizing athlete health and performance.

Purpose of the Study:

• To investigate the impact of a 4-month swimming training cycle on immune cell responses to high-intensity exercise.
• To analyze immune cell changes during 24 hours of recovery post-exercise.
• To consider the influence of sex, maturity, and age group on these responses.

Main Methods:

• Forty-three swimmers (males and females) underwent high-intensity exercise sessions at two points during their training macrocycles.
• Blood samples were collected pre-exercise, immediately post-exercise, and at 2 and 24 hours post-exercise.
• Haemograms and lymphocyte subsets were analyzed using automated cell counters and flow cytometry, with upper respiratory symptoms (URS) and training load also quantified.

Main Results:

• The second macrocycle (M2) showed smaller increases in leukocytes and neutrophils post-exercise compared to the first (M1).
• Lymphocyte recovery was less efficient at 2 hours post-exercise in M2, with a notable decrease in CD19+ cells.
• Age and pubertal status influenced immune cell recovery, with differing CD4+/CD8+ ratios in youth versus seniors and less efficient NK cell recovery in late pubertal swimmers.

Conclusions:

• The training cycle resulted in an attenuated immediate immune response post-exercise and less efficient lymphocyte recovery.
• An accentuated decrease in CD19+ cells was observed, potentially indicating immune suppression.
• Increased frequency of URS suggests a prolonged period of susceptibility to infection following intense training.