Stress and immune system

It has long been known that there is a relationship between physiological and psychological stress and immune function. The phenomenon that the concentration of immune markers decreases after heavy exercise (immunosuppression after exercise) is also well documented. Less well-researched, however, is the correlation between decreases in immune markers and upper airway infection (IOA) in athletes after excessive exercise.

A group of British scientists wanted to clarify this question in a study. For this purpose, 38 participants of the sailing regatta America's Cup were observed over a training period of 50 weeks. Saliva samples were taken from the athletes and the concentration of the so-called secretory immunoglobulin A (s-IgA) was measured. This is an antibody with an important protective function for the tissues of the upper respiratory tract (nose, throat and lungs). The samples were taken weekly, at least 38 hours after the last training session and always at the same time of day. The s-IgA measurements were then compared to the incidence of infection, exercise load and perceived fatigue.

In the weekly comparison, no significant relationship was found among the athletes between the absolute s-IgA concentration and the occurrence of an IOA. However, the s-IgA concentration showed marked interindividual fluctuations.

However, the scientists found that the s-IgA level decreased significantly in all participants in the 3 weeks prior to an upper respiratory tract infection. In addition, they observed that s-IgA usually returned to normal within 2 weeks of IOA. Another finding was that an athlete had a significantly higher risk of developing IOA if his s-IgA level dropped to below 40% of the average s-IgA concentration in a healthy state. As a rule, every second athlete fell ill (50:50).

The results of this study imply two things: even though athletes' s-IgA scores should not necessarily be compared, it has been shown that a decrease in s-IgA means a significantly higher risk for the individual in subsequent years 3 weeks to get an IOA. On the other hand, the relationship between s-IgA and the appearance of an IOA makes this marker a very useful control tool for coaches and athletes.

Medicine & Science in Sports Exercise. 2008, Vol. 40 (7), p. 1228-1236

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