Mucosal immunity and illness incidence in elite rugby union players across a season

Med Sci Sports Exerc. 2011 Mar;43(3):388-97. doi: 10.1249/MSS.0b013e3181ef9d6b.


Purpose: To examine the relationship between upper respiratory illness (URI) incidence with changes in mucosal immunity (saliva immunoglobulin A (s-IgA) and saliva lysozyme (s-Lys)) and training load (TL) in a squad of elite rugby union players.

Methods: Timed resting morning saliva samples were taken from players (n = 31) at preselected time points for 11 months. Weekly illness rates and TL were assessed using a Web-based diary and from medical/coaching staff reports.

Results: No significant correlation was found between absolute s-IgA or s-Lys concentrations and URI incidence. Peaks in URI (December and March) were preceded by periods of increased training intensity and reduced game activity. In 23% of all URI episodes, players reported that presence of an illness either reduced activity (14.4%) or felt the need to go to bed (8.6%). When s-IgA concentration was expressed relative to that when in a URI-free state, a 15% reduction (P = 0.08) was observed in individuals who had present URI symptoms. Decreases in absolute s-IgA (December) and s-Lys (November and February) concentrations were associated with a corresponding increase in saliva cortisol (P < 0.05). Lower s-IgA (P < 0.05) and s-Lys concentrations were consistently observed in backs than forwards, whereas URI incidence also differed for player position (3.4 forwards vs 4.3 backs).

Conclusions: Regular monitoring of s-IgA and s-Lys may be useful in the assessment of exercise stress and URI risk status in elite team sport athletes. A combination of alterations in training intensity and seasonal influence is a likely contributor to observed peaks in URI incidence. It is probable that stress-induced increases in cortisol release contribute to reductions in mucosal immunity, which, when lowered, predispose rugby players to increased risk of illness.

MeSH terms

  • Adult
  • Athletes / statistics & numerical data
  • Football*
  • Heart Rate / physiology
  • Humans
  • Hydrocortisone / immunology
  • Immunity, Mucosal*
  • Immunoglobulin A, Secretory / immunology
  • Incidence
  • Male
  • Muramidase / immunology
  • Oxygen Consumption / physiology
  • Respiratory Tract Infections / epidemiology*
  • Saliva / immunology
  • Young Adult


  • Immunoglobulin A, Secretory
  • Muramidase
  • Hydrocortisone