Aim: Concerns have been raised regarding the effects of prolonged intensive training on adolescent athletes. This study investigated the differences in mucosal immune functions and stress responses between intensively trained male adolescent volleyball players and age-matched sedentary controls.
Methods: Twelve male volleyball players (16.5 [0.7] years of age) and sixteen healthy sedentary male volunteers (17.1 [0.6] years of age) participated in this study. Volleyball players were engaged in regular and year-round training. Unstimulated saliva samples were collected from volleyball players during the high-intensity training period and from the counterparts at the same timepoints after at least 18 hours of rest. Concentrations of salivary total protein, secretory immunoglobulin A (SIgA), cortisol, and lactoferrin were measured.
Results: Results of this study revealed that the SIgA concentrations and the ratio of SIgA/total protein in volleyball players were significantly lower compared with those in sedentary controls. However, the salivary cortisol concentrations and the ratio of cortisol/total protein in volleyball players were markedly higher compared with those in sedentary controls. No significant difference was observed in lactoferrin levels between volleyball players and sedentary controls.
Conclusion: The findings of this study suggest that the prolonged intensive training may elicit a sustained stress and induce a suppressive effect on mucosal immunity in regularly and intensively trained adolescent athletes.