**3. Gut microbiota composition and physical activity**

Physical activity, especially moderate, has a positive effect on our body [34]. It can reduce metabolic and inflammatory diseases and influence the microbiota and health of humans and animals. Physical activity can be divided into the moderate level (< 70% VO2 max) and high-intensity level (> 70% VO2max). According to published studies, moderate physical activity has a positive effect on intestinal permeability, absorption and assimilation of food, and excretion of toxic metabolites [46]. In contrast, higher exercise intensity can negatively affect the digestive system and lead to the exercise-induced gastrointestinal syndrome, which affects 70% of athletes [47]. This may be the result of exercise-induced changes in the immune system of the digestive tract, leading to an increase in the inflammatory response and gastrointestinal symptoms [48].

The balance between exercise intensity, performance, and microbiota composition should be monitored for a long-time to optimize performance, health, and well-being and limit gastrointestinal syndromes.
