title: The impact of soccer training on the immune system.
abstract: 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.
  
  
  METHODS
  An observational study for one soccer season (one year).
  
  
  METHODS
  Professional soccer players.
  
  
  METHODS
  Thirteen professional soccer players (age: 26.3 +/- 3.7 years).
  
  
  METHODS
  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.
authors.affiliation: Faculty of Sport Sciences, University of Porto, Portugal.
authors.forename: A N
authors.initials: AN
authors.lastname: Rebelo
authors.forename: J R
authors.initials: JR
authors.lastname: Candeias
authors.forename: M M
authors.initials: MM
authors.lastname: Fraga
authors.forename: J A
authors.initials: JA
authors.lastname: Duarte
authors.forename: J M
authors.initials: JM
authors.lastname: Soares
authors.forename: C
authors.initials: C
authors.lastname: Magalhães
authors.forename: J A
authors.initials: JA
authors.lastname: Torrinha
mesh_terms: D000328:Adult; D016516:CD4-CD8 Ratio; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D005500:Follow-Up Studies; D006801:Humans; D007111:Immunity, Cellular / Q000276:immunology*; D007694:Killer Cells, Natural / Q000276:immunology; D007958:Leukocyte Count; D007962:Leukocytes / Q000276:immunology; D018655:Lymphocyte Count; D016131:Lymphocyte Subsets / Q000276:immunology; D009504:Neutrophils / Q000276:immunology; D012916:Soccer / Q000193:education / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology