Table 1.

PICOs criteria for inclusion and exclusion of studies

Parameter	Inclusion Criteria	Exclusion Criteria
Population	Healthy and unhealthy population, from sedentary lifestyle to professional athletes, no age limit	Animals, Subjects who take or have taken (before intervention) antibiotics, pre/probiotics or symbiotics
Intervention	Resistance training intervention, or measurement in specific strength athletes	Any kind of endurance PA/PE, combined PA
Comparison	Different type of physical activity (e.g., endurance, combined, HIIT) or control group without intervention	Absence of any kind of comparison
Outcomes	Alpha and beta diversities Taxonomical composition Microorganism abundance	Lack of measurements which are included in inclusion criteria
Study type	Observational studies Intervention studies	Systematic reviews, Meta-analysis, case study