The impact of soccer training on the immune system.

Objective: The aim of this study was to evaluate whether the level of some immune markers changed in soccer players during pre-season and during playing-season.

Design: An observational study for one soccer season (one year).

Setting: Professional soccer players.

Participants: Thirteen professional soccer players (age: 26.3 +/- 3.7 years).

Measures: The effect of 11 months of soccer training sessions and matches on circulating leukocyte and lymphocyte subpopulations was investigated. Blood samples were taken before the season and also 6 weeks, 6 months and 11 months later. All samples were taken at 08:00 h.

Results: Total lymphocyte counts did not change in all samples. During the pre-season, however, the concentrations of some inflammatory lymphocyte subpopulations were changed: CD4CD45RA+ was elevated and CD57 and CD8CD57 showed a significant decrease (p < 0.05), At the competitive period, CD4 and CD8 were increased. At the end of the season there were significant changes in some immune cells: total leukocyte and neutrophil number and CD8+ cell concentration was increased compared to pre-season values and the CD4/CD8 ratio was decreased.

Conclusions: The results suggest that athletes exposed to a long-term training periods can exhibit variations in some immune cells. The clinical significance of these variations requires more detailed investigation.