**1. Introduction**

Hard and under pressure training combined with stress caused by attending various competitions by reducing the physical and mental strength of individuals causes dysfunction in the immune system of professional athletes. Intense training, insufficient rest and improper nutrition are the factors that induce stress in athletes and make them prone to several health complications like immune depression, inflammatory dysregulation, increased respiratory tract infections, and mental stress [1–3]. Many epidemiological studies have reported that the symptoms of respiratory tract infections increase 1 to 2 weeks after strenuous endurance competition. The biological balance of the body's organisms improves host health, improves immune system function, and increases the body's defenses. Microbiota plays an important role in the physical performance of the host [4–6]. Dietary nutrients improve energy gain during exercise, which can bring many metabolic benefits to an athlete during exercise and recovery. Studies have shown that metabolic activity and related pathways increase in the microbiome of athletes compared to sedentary individuals [7–9]. Many studies have shown the benefits of probiotics such as reducing toxins, increasing immunity and resistance to infections, production of vitamins and nutrients, production of organic acids, reduction of allergic reactions and respiratory infections, arthritis and modulation of immune responses. Investigating the link between probiotic use and physical function, which shows that probiotics protect the body against undesirable physiological changes that may be caused by strenuous exercise. Probiotics can improve intestinal barrier properties [10] and antioxidant status [11]. Decreased physical performance and immune system strength following chronic fatigue in athletes who exercise intensively has been proven in many studies. Nieman et al. (2019) showed that regular and continuous exercise increases the strength of athletes' immune systems, while with heavy and intermittent exercise, the opposite results have been reported. The results of some studies show that heavy exercise, although It does not harm the organs, but it disrupts the immune system [12]. Humoral immunity in athletes is often assessed by measuring mucosal immunoglobulins A (IgA) and M(IgM) especially the amount of secretion changes from tissues in sports activities. Decrease in immunoglobulin After the intense sports activities, Increasd the possibility of upper respiratory tract infections. Lymphocytes play a very important role in the immune system due to the secretion of antibodies. Increasing the level of immunity and reducing the risk of disease in athletes, in addition to Increase their performance, will reduce treatment costs and improving immune function [13–19], so in this study, the effect of consumption of probiotic juice of *Bacillus coagulans* on the level of some immune system factors such as IgA IgM and lymphocyte Has been studied.
