(1) Purpose: Performing strenuous exercises negatively impacts the immune and gastrointestinal systems. These alterations cause transient immunodepression, increasing the risk of minor infections, especially in the upper respiratory tract. Recent studies have shown that supplementation of probiotics confers benefits to athletes. Therefore, the objective of the current study was to verify the effects of probiotic supplementation on cytokine production by monocytes and infections in the upper respiratory tract after an acute strenuous exercise. (2) Methods: Fourteen healthy male marathon runners received either 5 billion colony forming units (CFU) of a multi-strain probiotic, consisting of 1 billion CFU of each of Lactobacillus acidophilus LB-G80, Lactobacillus paracasei LPc-G110, Lactococcus subp. lactis LLL-G25, Bifidobacterium animalis subp. lactis BL-G101, and Bifidobacterium bifidum BB-G90, or a placebo for 30 days before a marathon. Plasma cytokines, salivary parameters, glucose, and glutamine were measured at baseline, 24 h before, immediately after, and 1 h after the race. Subjects self-reported upper respiratory tract infection (URTI) using the Wisconsin Upper Respiratory Symptom Survey (WURSS—21). The statistical analyses comprised the general linear model (GLM) test followed by the Tukey post hoc and Student’s t-test with p < 0.05. (3) Results: URTI symptoms were significantly lower in the probiotic group compared to placebo. The IL-2 and IL-4 plasma cytokines were lower 24 h before exercise, while the other cytokines showed no significant differences. A lower level of IL-6 produced by monocytes was verified immediately after the race and higher IL-10 at 1 h post. No differences were observed in salivary parameters. Conclusion: Despite the low number of marathoners participating in the study, probiotic supplementation suggests its capability to preserve the functionality of monocytes and mitigate the incidence of URTI.

Introduction and objective Moderate exercise performed in normoxia can be immunostimulatory, while strenuous exercise can be immunosuppressive. However, less is known about the effects of exercise under hypoxia on cytokines. The aim of this study was to evaluate the effects of an acute exercise session performed under hypoxia similar to an altitude of 4200 m on cytokine balance. Our hypothesis was that exercise, even of moderate intensity, associated with hypoxia may induce different changes in relation to the normoxic condition. Methods Eight healthy male volunteers were exercised on a treadmill for 1 hour at an intensity of 50% VO2peak under normoxic or hypoxic condition (4200 m). Blood samples were collected at rest and immediately 1 hour after the exercise, respectively to determine cytokines, hormones and metabolites. The two‐way ANOVA and the Bonferroni post hoc test were used and the significance adopted was P < .05. Results While IL‐2, the IL‐2/IL‐4 ratio and glutamine decreased under hypoxia, IL‐6 and IL‐1ra increased. There were increases in the IL‐2/IL‐4 ratio, IL‐6, IL‐1ra and IL‐10/TNF‐α in normoxia. There were no differences in cortisol or glucose. Conclusion Moderate exercise under hypoxia condition changes the Th1/Th2 balance including IL‐2, IL‐4 and TNF‐α cytokines, suggesting a Th2 response after 1 hour rest.