Training load, hormonal and immune responses, stress tolerance and upper respiratory tract infections in young soccer players

Abstract

There has been a substantial increase in research dedicated to determining the relationship between fitness level, immune function and steroids hormones. Among distinct approaches and research designs, there are those that aimed to investigate the relationship between hormonal changes and mucosal immunity, as well as, the impact of these parameters on the incidence and susceptibility to contracting upper respiratory tract infection (URTI)and changes in performance. The adaptation to physical or psychological stress usually involves the activation of the hypothalamic corticotropin-releasing-hormone, anterior pituitary adrenocorticotropic hormone, and adrenal glucocorticoids (cortisol and corticosterone) in anticipation of or during stressful situations understanding as a homeostatic response of the body. Among the hormones reacting to exercise and stress, cortisol is probably the more affected. Due to altered circulating levels with different forms of exercise, cortisol has been used to determine the physiological and psychological stress imposed during single and repeated exercise sessions. It has been proposed that metabolic stress stimulates the HPA, leading to an increased secretion of hormones such adrenocroticotropic hormone (ACTH) and cortisol, consistent with the increased susceptibility to contracting URTI. Various authors have utilized the salivary concentrations of immunoglobulin A (SIgA) to investigate the relationship between exercise training load, immune function and URTI incidence. Levels of salivary immunoglobulin A (SIgA) are lower in athletes engaged in heavy training. It has been suggested that changes in concentration of SIgA also may act as a marker of excessive training. In addition, psychological stress is also thought to influence mucosal immune function. Sustained periods of psychological stress have been associated with reduction in SIgA concentrations. Salivary immunoglobulin A concentration and secretion rate has been show to correlate more closely with URTI than changes in serum antibodies or other immune parameters. Although the implications of an observed impact on SIgA and salivary cortisol levels following heavy exercise are of great interest to sport scientists, relatively few data have been obtained in a true environment setting among young team sports athletes. Therefore, the aims of the present study are 1) to assess possible changes in SIgA and salivary cortisol after training and competitive sessions in young soccer players belonged to two distinct ages (under-15 and under-17 yr), 2) examine the impact of relative age, maturation status and anthropometric variables on salivary responses, and, 3)verify the association between ratings of perceived effort, SIgA and cortisol rest levels, with URTI occurrences within a training and competition season. (AU)