Stressful situations such as those derived from intense physical exercise can increase the incidence ofgastrointestinal disease episodes, particularly of diarrhea during heavy training (Mackinnon, 2000), and are likely to cause increased susceptibility to infections of the upper respiratory tract (Mackinnon, 2000) due in part to suppression of the functions of the immune systemsucceeding intense exercise sessions prolonged to exhaustion (Pedersen & Hoffman-Goetz, 2000).